Philosophy

Philosophy

EpistemologyIntermediate 2

Philosophy: Epistemology (Intermediate 2)

Acknowledgements

SFEU (Scottish Further Education Unit) gratefully acknowledges the contribution made to this publication by Learning and Teaching Scotland who have granted permission to use material previously produced by HSDU.

SFEU also thanks SQA for permission to reproduce parts of the Arrangement Documents.

Scottish Further Education Unit 0


Contents

Introduction 3

Statement of Standards: Unit Specification 5

Guidance on Learning and Teaching Approaches 7

Section 1: What is Knowledge? 9

Section 2 43- Option A: Descartes’ Rationalism 43- Option B: Humes’ Empiricism 77

Glossary 119



Introduction

Scotland has long been recognised as providing educational opportunities to its citizens that encompass both breadth and depth. The need to educate the whole person, and not simply concentrate on immediately obvious practical skills, is also firmly embedded in all Scottish educational philosophy. As a result, education focuses on the dual objectives of providing citizens with practical skills and knowledge related to employment, and broader intellectual and social skills which enable them to participate fully in society and lead rich, fulfilling lives. It is also recognised that these broader skills are increasingly important as societies become more complex and ideologically diverse. Scottish society today has bee influenced by a wide variety of cultures and traditions, and it is therefore important that all its citizens are able to develop and express their own values and perspectives in a reasoned way. In addition, it is important that they are able to discuss and reflect upon perspectives and values which may be different from their own. This can only be accomplished through a process of reasoned debate and discussion which acknowledges shared human experiences and also the validity of alternative views. Developing a structured approach to all forms of discourse will contribute to this process.

The opportunity for individuals to develop and discuss their own values and perspectives, and learn to appreciate those of others, is an important aspect of Scottish Primary and Secondary Education. For this reason the process of discussion, debate and reflection features in many areas of the curriculum from P1-S4. The Intermediate 2 Philosophy Course provides the opportunity for candidates to continue to develop the concepts and skills needed for productive social discourse and offers certificated progression in S5 and S6. The Course is also suitable for delivery in Further Education colleges and is appropriate for adult students who have an interest in philosophical issues.

Candidates who gain a Course award will be in a good position to continue their studies of philosophical issues at Higher level or in Further Education colleges. Those who choose to progress to study alternative subjects will also benefit. Developing basic critical thinking skills and the ability to reason in a structured way is an important part of the Intermediate 2 Philosophy Course and these skills are of relevance in all subject areas. This will help candidates to develop as members of society who can express their own opinions and values confidently but also appreciate the opinions and values of others.

The Course consists of four mandatory Units. The Critical Thinking in Philosophy Unit helps candidates to develop an understanding of good and bad arguments and develop basic reasoning skills. In the Metaphysics Unit candidates investigate aspects of a perennial philosophical debate and some of the positions adopted in relation to that debate. The Epistemology Unit focuses on questions surrounding the nature, sources and possibilities of knowledge. Moral Philosophy involves the study of issues and theories concerning moral judgements.

Aims

The Course aims to allow candidates to:

Develop basic critical thinking skills which are of importance in all areas of human life and discourse.

Develop knowledge and understanding of basic philosophical techniques, issues, positions and concepts which are relevant in many areas of human life and discourse.



Develop basic analytical and evaluative skills which help them to begin to examine the reasoning and assumptions on which the positions and theories they study are based.

Present their own ideas and opinions confidently and in a reasoned manner. Gain insight from the ideas and opinions of others which may conflict with their own. Engage personally with a range of important questions and issues in order to inform

their own ideas and opinions in a way which contributes to personal and social development.



Statement of Standards: Unit Specification

This Unit is a mandatory Unit of the Intermediate 2 Philosophy Course, but it can also be taken as a freestanding Unit.

This Unit offers progression for candidates who have studied an appropriate Intermediate 1 Course or Unit(s). It is also suitable as an Intermediate 2 level introduction for those who have no background in the subject. The issues studied in this Unit underlie many questions of both philosophical and general human interest such as: ‘Can we know what other people are thinking and feeling?’, ‘Can we know about things that we haven’t experienced?’ and ‘Can we be certain that the world will continue to work in the way it does now?’.

Candidates develop the knowledge and skills necessary to understand and examine philosophical issues in the area of epistemology. They do this by investigating specific epistemological issues which arise from the question: ‘What is knowledge?’. They also examine the position adopted by either René Descartes or David Hume in relation to this question. The chosen position is studied with reference to specific extracts from the writings of the relevant philosopher.

Specific philosophical questions, issues, positions and extracts are studied in this Unit but the critical thinking skills developed are relevant in a wide variety of contexts. These skills prepare candidates for the study of Philosophy at Higher or in Courses at Further Education colleges. Candidates will also be prepared for the study of any other subject which requires the critical analysis and evaluation of complex or abstract ideas. In addition, candidates will have demonstrated the skills necessary for entry into any field of employment where the ability to analyse basic issues and arguments and assess complex or abstract ideas, is required.

Epistemology (Intermediate 2)

In this Unit candidates study specific philosophical issues in the area of Epistemology. They also study aspects of the positions of either René Descartes or David Hume. The Unit is divided into two Sections and a brief overview of each Section appears below:

Section 1:

There is no choice of options in this Section of the Unit. All candidates must investigate the following question:

What is knowledge?

When investigating this question, candidates study a variety of issues and concepts in the area of epistemology.

Section 2:

In this Section of the Unit there is a choice of option to be studied. Candidates investigate aspects of either a specific rationalist or a specific empiricist epistemological position. The options are:



Option A: Descartes’ Rationalism

or

Option B: Hume’s Empiricism

Candidates must study all mandatory content in relation to their chosen option.The positions adopted by each philosopher are based on reasoning which can only properly be understood by examining the writings of the relevant philosopher. Candidates must therefore investigate the chosen position by studying key extracts from the writings of that philosopher. The key extracts are prescribed.

Outcomes

1. Demonstrate an understanding of philosophical issues in the area of epistemology. 2. Critically examine a standard philosophical position in the area of epistemology. 3. Critically assess a standard philosophical position in the area of epistemology.

Outcome 1

Demonstrate an understanding of philosophical issues in the area of epistemology.

Performance Criteria (a) Describe the tripartite theory of knowledge. (b) Describe specific philosophical problems associated with the tripartite theory. (c) Describe specific aspects of the key philosophical positions of scepticism, rationalism

and empiricism.

Outcome 2

Critically examine a standard philosophical position in the area of epistemology.

Performance Criteria (a) Describe specific aspects of the account of knowledge given by one specific

philosopher. (b) Explain the reasoning on which these aspects are based. (c) Cite specific extracts from the writings of this philosopher in support of the

explanation.

Outcome 3

Critically assess a standard philosophical position in the area of epistemology.

Performance Criteria (a) Explain the strengths and weaknesses of specific aspects of the account of

knowledge given by one specific philosopher. (b) State a position on the persuasiveness of this account of knowledge. (c) Give reasons to support this position.



Guidance on Learning and Teaching Approaches

In Section 1 candidates gain an understanding of some time-honoured issues in the area of epistemology. These issues are abstract in nature. Therefore care must be taken to illustrate them in a way that is accessible to Intermediate 2 candidates. The illustrations used are a matter for the professional judgement of the teacher or lecturer in light of the resources available and his/her knowledge of the prior experience of candidates. They might include discussing experiences or scenarios which will be familiar to candidates or investigating contemporary fictional treatments of the issues. For example, philosophical issues surrounding the problem of justification might be introduced through a discussion of optical illusions or popular films such as The Matrix and Total Recall.

Care must also be taken to ensure that candidates have a sound understanding of all issues in Section 1 of this Unit. Candidates will need this understanding to critically examine the position chosen in Section 2 in a meaningful way. It is therefore recommended that centres deliver Section 1 before investigating either position in Section 2. For the same reason, it is also of vital importance that candidates are familiar with all content in Section 1.

In Section 2, candidates study one option from a choice of two. The option chosen is a matter for the professional judgement of the teacher or lecturer in light of the resources available and his/her knowledge of the prior experience of candidates. Candidates must apply their understanding of the issues in Section 1 when critically examining and assessing this position. It is therefore important that teachers or lecturers maximise opportunities to integrate the understanding gained in Section 1 when delivering Section 2.

Candidates must also critically examine and assess the account of knowledge on which the position chosen in Section 2 is based. This can be accomplished only if candidates engage with the writings of the relevant philosopher; summaries and paraphrases do not always contain the relevant stages of reasoning. For this reason, it is essential that candidates are very familiar with all prescribed extracts. It is also recommended that prescribed extracts are used to introduce key stages in the relevant philosopher’s reasoning. Summaries or paraphrases of the writer’s ideas are useful when filling gaps between key stages in the argument or to help overcome problems with understanding or language. However, they should not be used as a substitute for a study of the key extracts.

For candidates who study this Unit as part of the Intermediate 2 Course, there are significant opportunities to integrate knowledge and/or skills in the remaining three Units. Understanding of issues and positions in the area of epistemology are also relevant when studying the Moral Philosophy and Metaphysics Units. In addition, the skills acquired during the study of the Critical Thinking in Philosophy Unit will help candidates to examine and assess the issues, positions and reasoning which they study in this Unit. Aspects of the skills of critical analysis and evaluation are relevant to all four Units in the Course. Candidates will have many opportunities to adapt and refine them in a variety of contexts while studying the Course.



All of the content of this Unit can also be studied in the Higher Epistemology Unit. If a centre makes the judgement that the Higher Unit would be more appropriate for a particular candidate, the candidate can be assessed at that level. However, it should be noted that there is additional content and differences in the skills being assessed at Higher. Additional learning and teaching will be required to ensure the successful completion of the Higher Unit in these circumstances.

If candidates go on to study the Higher Epistemology Unit there will be significant opportunities to build on and develop the knowledge and skills they have already acquired. However, it may be advisable to choose a different Option in Section 2 at Higher level. This will help to maintain student motivation and interest. It will also allow candidates to develop their knowledge and skills in a different context.



Section 1: What is Knowledge?

Contents

Teaching Outline 10

Teaching and Learning Approaches 11

Guide to Resources 12

Knowledge Handout 1 13– Knowing How and Knowing That

Knowledge Handout 2 16– The Tripartite Theory of Knowledge

Knowledge Handout 3 22– Sources of Justification: Rationalism– Problems of A Priori Justification

Knowledge Handout 4 26– Sources of Justification: Empiricism– Problems of A Posteriori Justification

Knowledge Handout 5 31– Scepticism

Sample Activities 34

Suggested Answers 40



Teaching Outline

The materials in this part of the pack are for Learning Outcome 1 of the Intermediate 2 Epistemology unit, introduced by SQA in 2006. This part of the unit is intended both to introduce students to the key philosophical issue of knowledge and its acquisition, and prepare them for the later study of an early modern philosopher working in this field – either Descartes or Hume.

One of the innovations of the revised Intermediate 2 Philosophy is a greater emphasis on extracts from primary texts. It is expected that students will be able to demonstrate some familiarity with the text chosen, and be able both to explain and to evaluate the philosopher’s response to the philosophical questions under examination. Given that this will involve close reading of extracts in class with students, it is anticipated that this part of the unit will cover approximately one third of the work of the typical class, with the remaining two thirds being devoted to work on the chosen primary text.

The rationale behind this part of the unit is that students must become familiar with a body of epistemological issues and concepts as a preparation for engagement with the texts of either Descartes or Hume. The unit thus introduces epistemology as one of the main branches of a discipline whose concern is the attempt to clarify and to justify our important beliefs (a centrally important belief being that it is possible for us to gain knowledge). Students are then introduced to an area of perennial philosophical concern – namely, the fact that many of the concepts which we employ pre-philosophically are in fact ambiguous. This is, of course, the case with regard to ‘knowledge’. It is intended that by examining why epistemology is important, and how the claim that we have knowledge is potentially ambiguous, students will come to think philosophically – asking questions such as ‘what does this mean?’, ‘is it true?’, and ‘how is this important?’.

This part of the unit then shifts from the general to the particular, introducing the traditional tripartite model of propositional knowledge, and considering the three elements of belief, truth and justification. Philosophical terms are introduced as required. Students should be encouraged to learn and to apply these; while it will be adequate for assessment purposes that students can point out that belief, truth and justification are three conditions which must be met in order for us to have propositional knowledge, a good candidate will be able to explain that these conditions are individually necessary and jointly sufficient. It is the intention of these packs that the terminology of the subject will be taught alongside the substantive content – and that students will be encouraged to learn both.

The Rationalism/Empiricism debate is introduced in terms of the problematic justification condition. The thinking behind this part of the unit is that irrespective of which of the philosophers teachers opt to study for the other two learning outcomes, it is necessary for students to have a grounding in the debate. Descartes makes a conscious decision to reject empiricism, and Hume to reject rationalism – and students should be aware of the putative strengths and weaknesses of the rejected position, as well as studying the philosopher’s argument for his preferred approach to the gaining of scientific knowledge. Once again an important element in students’ learning is the acquisition of a body of relevant and appropriate philosophical terminology – so that students can do more than merely recall a list of key points, and ‘strengths and weaknesses’.



Finally, there is a brief introduction to three enduring epistemological problems: the problem of other minds; the reliability of authority; and the problem of induction. By this stage in their study, students should be able to relate these problems to the tripartite theory. Equally importantly, they should see how important beliefs which are central to our everyday lives may be revealed as philosophically interesting and problematic when we clarify them and question the possibility of their justification.



Teaching and Learning Approaches

Extensive guidance on teaching and learning approaches is provided in the Course Specification, and teachers are referred to these at www.sqa.org.uk This part of the pack introduces some simple scenarios which can be the basis for class discussion. These – and examples from film and television – tend to be particularly helpful in getting students to recognise both the importance, and the philosophical interest, of the issues covered in this study unit. Good students may identify examples of their own which are especially useful in class discussion, and which will help to consolidate understanding of the topic, and familiarity with the terms and concepts employed by epistemologists.


http://www.sqa.org.uk/


Guide to Resources

A number of texts have been published in recent years which introduce epistemology at a level appropriate to Intermediate 2. Particularly recommended are:

Cole, P. (2002) The Theory of Knowledge. Hodder & Stoughton.

Cardinal, D. et al (2004) Epistemology – The Theory of Knowledge. Hodder Murray.

Most general textbooks are either pitched at the A level/first year undergraduate market, and/or they concentrate on epistemological issues which are beyond the narrower confines of Intermediate 2 Philosophy. The following may, however, be useful for teachers in preparing tutorials:

Hospers, J. (1997) An Introduction to Philosophical Analysis. Routledge.

Morton, A. (1996) Philosophy in Practice – An Introduction to the Main Questions. Blackwell.

A fashion has recently grown for Philosophy Through Film. For students or teachers who have seen the ‘Matrix’ trilogy, the following unconventional text may provide useful material:

Lawrence, M. (2004) Like a Splinter in Your Mind – The Philosophy Behind the Matrix Trilogy. Blackwell.

There are dozens of websites, of varying scholarly quality, which discuss the philosophy behind The Matrix. The best is the official Warner Brothers site, which has material on the Brain in a Vat and other related philosophical topics. It is available at:

http://whatisthematrix.warnerbros.com/rl_cmp/phi.html


http://whatisthematrix.warnerbros.com/rl_cmp/phi.html


Knowledge Handout 1

Knowing How and Knowing That

Philosophers are interested in knowledge. This will not surprise you – even if you have never studied any philosophy before, you will expect that philosophers are interested in gaining philosophical knowledge – just as historians seek historical knowledge, and mathematicians seeks mathematical knowledge, biologists seeks biological knowledge, and so on.

Clearly a philosopher does want philosophical knowledge. But there is a more important point to make here. Historians and mathematicians and biologists want knowledge – but they don’t ask what ‘knowledge’ is. They take it for granted that there is knowledge, and then set out to find it. Philosophers are different. They ask questions such as ‘what is knowledge?’, and ‘is it possible to have knowledge that is 100% reliable – knowledge that is absolutely certain?’. This is what we are to be studying in the Epistemology unit of Intermediate 2 Philosophy.

Let’s see how this fits in with a definition of ‘philosophy’.

Philosophy is an activity.

When we are doing philosophy, we are trying to do two things:

1. We are trying to clarify our important beliefs.2. We are trying to justify our important beliefs.

One of the important beliefs that we all have is that knowledge is possible – that we can gain knowledge by various means. One of the reasons for studying Intermediate 2 Philosophy is, after all, that you want to have knowledge of Philosophy. But you also want to have knowledge of many other things: whether it will rain today; what books you need for your course; when the class begins; who can tell you what you need to revise for the exam; where the exam will be held; and so on.

We go through life taking for granted that knowledge is possible – and that gaining knowledge is straightforward – so that by the time we are in our teens, we have already learned an enormous amount (and that one of the most important differences between a 16-year-old person and a 16-week-old person is the massive amount of learning – ‘knowledge-acquisition’ – that the 16-week-old has ahead of him or her).

If we think about the definition of ‘philosophy’ given above, we can see, then, that there are two tasks for philosophers:

1. Getting clear what it means to say that we have knowledge (this is the ‘clarifying’ part).

2. Proving that knowledge is possible (this is the ‘justifying’ part).

Philosophers who deal with these questions are ‘epistemologists’. The word ‘epistemology’ was introduced into philosophy by a nineteenth century Scottish philosopher, James Ferrier. It is made up of two Greek words. In Greek ‘episteme’ means ‘knowledge’, and ‘logos’ means ‘explanation, or study’. So ‘epistemology’ is the study of knowledge.



It may seem that the epistemologist’s questions aren’t worth asking. How can we doubt that we have knowledge? How can there be any question about what knowledge is? This raises an important point about philosophy. Philosophers tend to take nothing for granted. Philosophers will generally be very suspicious of the notion that ‘it’s just obvious’. What do we mean when we say that we have knowledge?

Think about the ways in which we use the verb ‘to know’:

1. I know that David Hume died in 1776.2. I know how to use this software.3. I know who committed the ‘Jack the Ripper’ killings.4. I know the quickest way to get from Glasgow to Edinburgh.5. I know French.6. I know France.

This short list contains three different uses of the word to ‘know’. So if we are to clarify what it means to say that we have knowledge, then we will have to start by getting clear what are these three, and how they differ.

Firstly, there is the use of ‘know’ in example 1: I know that … – where what comes after the word ‘that’ is a statement (also known as a ‘proposition’). In the case of example 1, we have three things:

a) The proposition ‘David Hume died in 1776’.b) The person who is making the claim – ‘I’.c) The relationship between the person and the proposition – here a relation of

‘knowing’.

Notice how this is different from example 2. In example 2, what is known is not a fact (a true proposition such as ‘David Hume died in 1776’), but rather how to do something. This is the kind of knowledge that we have when we have ‘know-how’. So if I know how to write HTML code on a computer, or how to bake a cake or solve simultaneous equations, then I have this kind of knowledge.

Example 3 is really just the same kind of knowledge as was example 1 – what we call ‘propositional knowledge’. Whereas in example 2 the target for knowledge is some skill, such as a mathematical skill, or a baking skill, in examples 1 and 3 the target for knowledge is a proposition – ‘David Hume died in 1776’, or ‘The Prince of Wales was Jack the Ripper’.

Example 4 can be thought of either as propositional knowledge, or as know-how. ‘I know the quickest way to get from Glasgow to Edinburgh’ could be set out as:

a) I know how to get from Glasgow to Edinburgh by the quickest method.b) I know that the quickest way to get from Glasgow to Edinburgh is by hiring a

helicopter.

People who are training to drive black taxis have to ‘do the knowledge’. What this means is that they have to know their way around the city so well that they can pass a rigorous examination before getting a licence. Here again we can think of their knowledge in one of two ways: the Edinburgh taxi driver needs to know how to get from Waverley station to the Scottish Parliament; alternatively s/he has to know that Waverley Station is at Waverley Bridge, and the Scottish Parliament is at Holyrood.



‘I know French’ (example 5) is, of course, an example of know-how. What it means is ‘I know how to speak French’.

Finally, example 6 is importantly different. ‘I know France’ means ‘I am familiar with France, having been there’. This is really a third way of using the verb ‘to know’: it is what philosophers call knowledge by acquaintance. If I say that I know the paintings of Gauguin, or that I know the man who wrote the book or know the Beethoven Violin Concerto, then this means that I am acquainted with – I have been in some kind of contact with the man (whom I have met), the paintings (which I have seen), or the music (which I have heard). Notice how our Edinburgh cabbie can also be said to have knowledge by acquaintance (of course: he needs to be very familiar with Edinburgh).



Knowledge Handout 2

The Tripartite Theory of Knowledge

As we have seen, the word ‘knowledge’ is used in different – though related – ways. Philosophers are interested in all these, but our concern in this course is with propositional knowledge. Propositional knowledge is knowing that. My knowledge that a straight line is the shortest distance between two points, or that the sun is shining outside my room as I write this, are examples of propositional knowledge.

I have just claimed to have two pieces of knowledge. I know that:

1. A straight line is the shortest distance between two points.2. The sun is shining outside my room.

What are the conditions for my having propositional knowledge?

Consider the following story:

Fred is taking part in a psychology experiment. The experimenters tell Fred that they are giving him a powerful mind-altering drug, which will make all women look like his mother. Fred believes them, although the drug which they give him is actually only an ordinary aspirin.

The point of the experiment is to test whether he will think that women look like his mother just because he expects them to do so. Fred’s mother is a telephone repair engineer, and has been called to fix a telephone in the psychology department. By mistake she walks into the laboratory where Fred is.

‘Ha ha’, says Fred. ‘Good trick – how did you find out that my real mother is a telephone engineer?’.

Think about this story – and before turning the page, ask yourself: does Fred know that the woman is his mother?



The answer is, surely, that Fred doesn’t know that the woman is his mother. He believes that the psychologists have given him a drug which really will have the effect that they claim (so that any woman who comes into the room will look like Fred’s mother). Because he believes this, he does not believe that the woman is his mother – even though it is true.

It is a necessary condition for having knowledge that I have belief. A necessary condition is, as the term suggests, a condition which must be met (so that, for example, it is a necessary condition for being someone’s sister that you are female. If you are not female, then you just can’t be a sister).

We need to be careful here. Sometimes people say things like:

Well, I know that Iceland beat Scotland – but I don’t believe it.

This seems to be suggesting that you can have knowledge and not have belief – that is, it seems to be suggesting that belief is not, after all, a necessary condition for knowledge. But someone who says, ‘I know that Iceland beat Scotland – but I don’t believe it’ is not making a sincere statement. This is an example of hyperbole – of exaggerating for effect. What the person who says this really means is something like: ‘I know that Iceland beat Scotland – but it’s a very surprising result’. Presumably football fans don’t want to say things in conversations with each other such as ‘I’m very surprised’. ‘I don’t believe it!’ – even when the evidence is staring you in the face – gets your point across more effectively.

So however people use language in everyday speech, we cannot really claim to have knowledge that something is the case when we don’t believe that it is the case.

Remember that what we are discussing here is propositional knowledge. Philosophers sometimes use the letter ‘p’ to stand for any proposition (in the same way that in algebra, ‘x’ and ‘y’ and ‘z’ can be used to represent any value). So ‘p’ could stand for ‘a straight line is the shortest distance between two points’, or for ‘the sun is shining outside my room’ – or for any other proposition. We can now bring all of this together, and say that:

I cannot know that p unless I believe that p.

Or, in other words, it is a necessary condition for my knowing that p that I believe that p.

Now consider the following extract, taken from a website:1

‘The facts are simple,’ says Charles K. Johnson, president of the International Flat Earth Research Society. ‘The earth is flat.’

As you stand in his front yard, it is hard to argue the point. From among the Joshua trees, creosote bushes, and tumbleweeds surrounding his southern California hillside home, you have a spectacular view of the Mojave Desert. It looks as flat as a pool table. Nearly 20 miles to the west lies the small city of Lancaster; you can see right over it. Beyond Lancaster, 20 more miles as the cueball rolls, the Tehachapi Mountains rise up from the desert floor. Los Angeles is not far to the south. Near Lancaster, you see the Rockwell International plant where the Space Shuttle was built. To the north, beyond the next hill, lies Edwards Air Force Base, where the Shuttle was tested. There, also, the Shuttle will land when it returns from orbiting the earth. (At least, that’s NASA’s story.)

1 http://www.lhup.edu/~dsimanek/fe-scidi.htmb


http://www.lhup.edu/~dsimanek/fe-scidi.htmb


‘You can’t orbit a flat earth,’ says Mr. Johnson. ‘The Space Shuttle is a joke – and a very ludicrous joke.’ His soft voice carries conviction, for Charles Johnson is on the level. He believes that the main purpose of the space program is to prop up a dying myth – the myth that the earth is a globe. ‘Nobody knows anything about the true shape of the world,’ he contends. ‘The known, inhabited world is flat. Just as a guess, I’d say that the dome of heaven is about 4,000 miles away, and the stars are about as far as San Francisco is from Boston.’

Charles K. Johnson really believes that the earth is flat – and that NASA is part of a conspiracy which is trying to fool us all into believing that it is in fact a globe.

Does Charles know that the earth is flat? Think about this before turning the page.



The problem with Charles Johnson’s claiming to know that the earth is flat is that it is not. He may sincerely believe that the earth is flat, but his belief is a false belief. In the middle ages everyone believed that the earth was stationary. They would have claimed, if asked, to know that the earth was stationary. We now know that it is moving around the sun at about 30 kilometres per second (ie. about 18½ miles per second).

Note how Charles Johnson meets one of the necessary conditions for having knowledge: he has a belief (and it is a sincere belief). But even though he satisfies this condition, he still does not have knowledge that the earth is flat.

What this shows is that while the belief condition is a necessary condition for knowledge, it is not a sufficient condition. A sufficient condition for knowledge – as the term suggests – is a condition which, if met, guarantees that we have knowledge. Think back to the ‘sister’ example earlier. It is a necessary condition for being a sister that you be female (you cannot be a non-female sister). But being female is not sufficient, because you could be an only child. So being a sibling is a further necessary condition (and again, this one by itself is necessary but not sufficient). There are two individually necessary and jointly sufficient conditions for being a sister:

being female being a sibling.

Notice how we can define a sister as being ‘a female sibling’. All sisters are female siblings – and all female siblings are sisters.

The ‘flat earth’ example shows that a further necessary condition for having knowledge is that the proposition in question is true. This is the truth condition. The proposition ‘the earth is flat’ is false – and so it cannot be an object of knowledge.

Now take a moment to think about how Fred (the participant in the psychology experiment) and Charles Johnson (the President of the Flat Earth Society) are alike, and how they differ. Do this before turning the page.



Fred and Charles are alike in that neither has knowledge. Fred does not know that the telephone engineer is his mother, and Charles does not know that the earth is flat.

The two differ, in that Charles has a belief – but what he believes is false.

Fred does not believe that the woman is his mother – but what he does not believe is true.

We now have two individually necessary conditions for knowledge. Are these jointly sufficient (in the same way that being a sister and being a sibling are jointly sufficient for being a sister)?

It may seem surprising, but in fact it is possible to have a true belief but not have knowledge. To see this, consider the following case.

Suppose I have been given some mind-altering drug without my being aware of it (it has been slipped into my coffee this morning). The effect of the drug is to make me go through the rest of the day compulsively making predictions, which I will sincerely believe to be true.

I tell you that I know the numbers which are going to come up in next Saturday’s lottery draw: 5, 11, 13, 28, 33, 34. I am so certain that these numbers are going to come up that I force you to write them down – which you do to humour me.

On the following Sunday, you happen to notice the previous evening’s lottery results, and the numbers look strangely familiar. You go to find the scrap of paper on which you copied down my forecast, and there are the very same numbers that are in the newspaper: 5, 11, 13, 28, 33 and 34 (no-one won the jackpot, which was £10 million).

Amazed (and a little sorry for having mocked me), you ring me to ask how I knew that these numbers would come up. By now the drug has worn off – but I still don’t know that I was drugged. ‘How did you know that these numbers would come up?’, you ask. ‘Well’, I reply, ‘I just felt it in my water.’

Note how, like Charles Johnson, I had a sincerely held belief. Unlike Charles, my belief turned out to be true. Would you say that I knew that these numbers would come up in the lottery? Think about this before turning the page.



The answer is, surely, that I did not know. A lucky guess, or a hunch that turns out to be true, is not knowledge.

The key question in this last example is: ‘how did you know that these numbers would come up?’. The answer ‘I felt it in my water’ is just not a satisfactory answer to that question (nor is ‘I just did’. Think of the number of times that you have replied to the ‘how do you know?’ question by saying ‘I just do’).

To have knowledge, we need to be – to use a common expression – ‘in a position to know’. If the national lottery was actually rigged, and if I was a national lottery official, then I might be ‘in a position to know’ what numbers were coming up next Saturday. In answer to the question ‘how did you know that these numbers would come up?’, ‘the thing is rigged, and I’m in on it’ is a satisfactory answer (at least from an epistemological point of view). ‘I just did’ is not a satisfactory answer – it does not provide justification for a claim to have knowledge.

So I can have a true belief yet not have knowledge. The belief condition and the truth condition are individually necessary, but are not jointly sufficient for knowledge. A third condition must also be met – the justification condition. This condition is met when I can give a satisfactory answer to the question ‘how do you know?’.

So knowledge is justified, true belief. The three conditions – the belief condition, the truth condition and the justification condition are individually necessary and jointly sufficient for knowledge.

Finally, it may have occurred to you that the term ‘satisfactory answer’ is a little unclear. What makes an answer to this question a satisfactory answer, and how can I be sure that my answer is satisfactory? This question is a major one for philosophers such as Descartes and Hume – both of whom recognise that what we may take to be justification may in fact not after all be justification. Think of the people who thought that the earth was stationary. What more justification would you need than the fact that you can see it and feel it to be stationary? The history of humanity is to a great extent a history of our discovering that we have got things wrong – that what we had taken ourselves to know (sometimes with great confidence) was in fact wrong. Clearly, when we have had false beliefs which we took to be knowledge, we were mistaken in thinking that these beliefs could be justified. This leaves us with an unsettling question: what are the errors which we are making today, and which future generations will discover?



Knowledge Handout 3

Sources of Justification: Rationalism

The justification condition is the most troublesome of the three conditions for knowledge – and much philosophical effort has gone into answering the question of how we can ever justify our knowledge claims.

One way of answering the ‘how do you know?’ question is by using reason. Think of the following statement:

Everybody who is a sister is female.

How do you know that everybody who is a sister is female? One way would be to check sisters – to see if any of them were male. You could check lots and lots of sisters; once you’d realised that all of the sisters that you had checked were female, you might come to the conclusion that all of them are. There are two things to notice about this:

1. It is not absolutely guaranteed to be reliable (if you haven’t checked every single one of them, can you be certain that there are no non-female sisters?).

2. You don’t need to do this anyway. The truth of the claim that all sisters are female does not need to be checked in this way.

‘Everybody who is a sister is a female’ is an example of a truth which can be known independently of experience. The philosophical term for this is that it is an a priori truth. A priori truths are known to be true prior to experience. Before doing any checking, we know that all sisters are female. This is true by definition. If we take, by contrast, the statement:

Everybody who is a sister is shorter than seven feet tall.

We can’t check this for truth or falsity just by thinking about it. This statement is an a posteriori statement. A posteriori statements are known to be true (or false) as a result of experience – in this case, as a result of checking to see whether there is evidence of anyone having been a sister, and having been 7 ft tall or more.

So a priori knowledge is knowledge which we gain just by thinking. The justification condition is met merely by reflecting mentally on the meanings of the words ‘all’, ‘sisters’, and ‘female’.

Here are some more examples of knowledge which we arrive at a priori:

All bachelors are unmarried. If Dundee is south of Aberdeen, then Aberdeen is north of Dundee. If Dundee is south of Aberdeen, and Edinburgh is south of Dundee, then Edinburgh is

south of Aberdeen. Anyone who is 7 ft tall is more than 6 ft tall.

Remember that the key question with which we are concerned is the justification question – the ‘how do you know?’ question. In the case of the statement ‘all bachelors are unmarried’ we can answer this by doing some simple reasoning:



1. There are two necessary conditions for being a bachelor – these are (a) being unmarried, and (b) being a man.

2. These two conditions are, therefore, individually necessary and jointly sufficient, so that:

3. We can define a bachelor as an unmarried man – and substitute ‘unmarried man’ for bachelor.

4. The statement can therefore be rewritten as ‘all unmarried men are unmarried’ – and this just has to be true.

This is an example of what philosophers call ‘conceptual analysis’. To analyse is to break something down into its component parts. We break down a concept by finding its necessary and sufficient conditions.

In the statement ‘all bachelors are unmarried’, the subject (what the statement is about) is ‘all bachelors’, and the predicate (what is being claimed about the subject) is ‘are unmarried’. The predicate is here contained in the subject – and we just have to think about the meaning of the statement to see that it is true. Its meaning guarantees its truth. A statement where the meaning guarantees the truth in this way is called an analytic statement. In an analytic statement, the meaning guarantees the truth (and we see this by analysing the concepts which it contains – in the above case, by analysing the concept ‘bachelor’).

Any statement which is not analytic is synthetic.

Some philosophers have come to think of reason as the most reliable source of justification – as the best way of answering the ‘how do you know?’ question – because truths which are a priori discoverable are absolutely certain. Think of the following piece of knowledge:

A straight line is the shortest distance between two points.2

This statement is true. I believe it – and you should believe it. If I am asked ‘how do you know?’, my response will be that we just need to think about the statement to grasp its truth. So it is justifiable a priori.

There is another point to make about the statement, though. It is not only true: it is true and could not possibly not be true. It is, to use the philosophical term, necessarily true. This term – not to be confused with ‘necessary conditions’, which we came across earlier – is used to describe all those statements which are true and not possibly not true.

Notice that we do not get the same certainty when we move from a priori to a posteriori truths. The statement:

The edge of my desk is a straight line.

is true – but it is not necessarily true (it is only contingently true). The world could have been such that the edge of the desk was curved (I have another desk which is curved). Philosophers sometimes express this by imagining other possible worlds, which are just like this world except for some particular detail.

2 On a plane surface – which should be assumed in what follows.



There could be another world in which every single detail is just as it is in this world, but this desk has a curved rather than straight front. Crucially, though, there is no possible world in which there are straight lines which are not the shortest distance between two points (or where there are non-female sisters or married bachelors).

So a priori discovery of knowledge is the discovery of knowledge which is – apparently – absolutely impossible to doubt. It is true in any possible world – necessarily true; true and not possibly not true.

Rationalists (whose name comes from the Latin word ratio, which means reason) see reason as the most reliable source of justification because rationally (ie. a priori) discoverable knowledge passes the ‘possible worlds’ test, and so is just impossible to doubt.

Problems of A Priori Justification

There is, however, a problem with a priori justification. To see this, consider two possible ways in which I might answer the question: ‘what day is it?’:

1. It is Tuesday.2. Either it is Tuesday or it is not.

Both (1) and (2) are true as I write this. Statement (1) is a posteriori (I need to observe something – the masthead of today’s newspaper, the introduction given by the news announcer on the radio, the clock on my computer, etc.) in order to know that today is Tuesday. It is also contingently true that today is Tuesday: the world could have been different (at various times in history calendars have been revised – so this could have happened, with the result that today is Thursday).

Statement (2) is, of course, a priori. I just need to think about it to see that the statement ‘either it is Tuesday or it is not’ is necessarily true – true and not possibly not true. But here is the problem: it is always the case that either it is Tuesday or it is not Tuesday.

What this shows is that statement (1) is informative, but statement (2) is really not informative. Statement (2) is in fact useless, trivial knowledge. What I want to know if I ask you what day it is, is whether I have classes today, whether the cheque which I paid into my bank has cleared, whether my favourite television programme is on this evening, and so on. If you tell me that it is Tuesday, I can infer from that the answers to these and many other questions (to ‘infer’ is to form a belief. If today is Tuesday and my favourite programme is on television every Tuesday, I infer from that that my favourite programme is on today). If you merely tell me that either it is Tuesday or it isn’t, then I can really do nothing at all with that information – even though it is necessarily true.

Here’s another example of the apparent uselessness – the triviality – of necessary truths which are a priori discoverable. Consider the following statement:

Nothing can be bigger than itself.

Clearly this is a priori and necessary. No mountain can be bigger than itself, no river deeper than itself, no elephant heavier than itself, and so on.

If we apply this to alien life forms on other planets, we get:

No aliens are bigger than themselves.



This is a true statement about aliens on other planets. Do you find this useful, or interesting, or informative?

Reason, in short, is limited in what it can give us as knowledge. It can tell us how the universe has to be – all straight lines have to be the shortest distance between two points, it always has to be either earlier or later than 6pm, all red roses have to be red, all sisters are female, and all aliens are no bigger than themselves. But surely what we really want to know is: are there alien life forms on other planets? What mathematical knowledge do they have? What kind of vegetation does their planet sustain? Are there males and females, and do they have family units which resemble ours? It is a fascinating thought that if they are intelligent, then these aliens will have much the same geometrical knowledge as we have – but beyond that, a priori truths about them are rather trivial and unimpressive. If all that they know about us is that if we exist, then none of us is bigger than ourselves, then they really don’t know anything interesting or useful about us – do they?



Knowledge Handout 4

Sources of Justification: Empiricism

If reason only gives us trivial knowledge – knowledge of what has to be the case, rather than of what happens to be the case – then perhaps we ought to rely rather on the senses, and on a posteriori knowledge. A posteriori knowledge may be only contingent (true, but could conceivably have been false – false in other possible worlds), but it is useful – informative – knowledge.

It seems in any case natural to us to rely on the senses as the basis for justifying our claims to knowledge. We have expressions such as ‘seeing is believing’; our sense of sight is particularly important in this respect (think of the expression ‘I have seen it with my own eyes’; what we are doing here is justifying a knowledge claim a posteriori). From our earliest moments, we learn about the world through touch – and later through seeing, hearing, smelling and tasting. As the 17th century French philosopher René Descartes puts the point:

Surely whatever I had admitted until now as most true I received either from the senses or through the senses. (Meditation 1)

So the most natural way for us to meet the justification condition for knowledge is via observation – via the senses.

Philosophers who employ sense experience as the source of justification are empiricists (the word ‘empiricist’ comes from the Greek word for ‘experience’).



We saw earlier that the statement ‘everybody who is a sister is female’ is:

a priori analytic necessarily true.

Now consider the statement:

My sister is over five feet tall.

Here we have an example of a statement which differs in all three respects from the last statement.

Firstly, the statement is a posteriori. Clearly, if I am asked ‘how do you know that your sister is over five feet tall?’, I cannot respond by saying ‘well, just think about it’. I would have to measure her, or ask her, or get her to stand beside something which I know to be five feet in height, so that I could look and compare. So I know that my sister is a female sibling without having to observe anything – but I do need some kind of observation in order to know that she is some particular height.

The statement is also not analytic. Remember how we were able to break down the concept ‘sister’ into its necessary and sufficient conditions – and, by this conceptual analysis, discover that all sisters are female. Although it is a necessary condition for my sister’s being a sister that she be female, it is clearly not a necessary condition for her being a sister that she be over five feet tall. So the statement ‘my sister is over five feet tall’ is synthetic. That is to say that the statement synthesises – joins together – the subject (‘my sister’) and a predicate which is not contained in that subject (‘over five feet tall’). So whereas the predicate ‘female’ is contained in the subject ‘sister’, the predicate ‘over five feet tall’ is not contained in the predicate – it adds new information.

Finally, the statement ‘my sister is over five feet tall’ is contingent. That is to say that if it is true, then it is contingently true, and if it is false, it is contingently false. For a statement to be contingently true is for it to be the case that it could conceivably have been false (there are possible worlds in which my sister is under five feet in height).



Here are some more examples of knowledge which we arrive at a posteriori:

Some bachelors are happy men. Dundee is south of Aberdeen. The population of Dundee is smaller than that of Aberdeen. Anyone who is 7ft tall is too big to get into a Mini.

You should compare these examples with the examples of knowledge arrived at a priori – on p. 24 of this unit.

One of the advantages of this kind of knowledge is that it is informative. A sociologist may find it interesting that in our society some men are both unmarried and happy. If you are in Aberdeen, and want to get to Dundee, then it is useful to know that you need to head south (the a priori knowledge that ‘either Dundee is south of Aberdeen or it is not’ is really useless knowledge, if what you want to do is get to Dundee). If you are planning the distribution of census forms in the north east of Scotland, or arranging to give Britain’s tallest man a lift in your Mini, then it is clearly helpful to know that Aberdeen is bigger than Dundee, and that the man won’t fit into your car.



Problems of A Posteriori Justification

There are some problems with a posteriori justification.

1. Everyone has had experience of optical illusions – such as the road which appears to shimmer on a hot day. Other senses are also liable to be tricked in this way (when you put your hand inside a polythene pocket, static electricity makes the surface of the plastic feel ‘furry’). So there seems to be an element of unreliability about at least some of our observation-based knowledge. Can we be certain that we always know when our experience is illusory?

2. Hallucination can lead us to see or hear things which just aren’t there at all. In his play Macbeth, Shakespeare shows us how mentally disturbed Macbeth is as he prepares to murder King Duncan by having him hallucinate a dagger. Macbeth tries to grasp the dagger which he thinks he sees – but can’t, because there is no dagger there. As with illusions, there is a question here: can we be certain that we always know when our experience is the result of a hallucination?

3. Human beings can see colours that dogs can’t. This is because of facts about human brains and canine brains, and the proportion of the two which is dedicated to visual perception (dogs have a more acute sense of smell than humans, because more of their brains deal with smell). We tend to assume that what this shows is that our perception is more ‘reliable’ than dogs’ perception. Surely what it shows is that perception is ‘species-specific’. How do we know that there aren’t aliens, elsewhere in the universe, who are more highly evolved than we are (and perhaps have senses which we don’t have at all – like the sense of echolocation which bats have)? Wouldn’t the aliens encounter the world differently from the way in which we do – and wouldn’t they think that their perception was more reliable than ours?

4. As well as being species-specific, our perception is ‘theory-laden’. What this means is that what we see or hear depends upon a set of background assumptions – ‘theory’. Take, for example, a musical score. A trained musician will ‘see’ a melody – and ‘hear’ it in his head. For someone who can’t read music, the score will simply be spots and symbols on a piece of paper. There is evidence that people from cultures very different from our own have learned to see the world differently from the way in which we do – so that again a ‘theory’ is at work in leading us to interpret what we see. We may be completely unaware of this, of course. If we are, then we may well take our experience to be just what anyone else’s would be.

5. Some philosophers have questioned whether we can be certain that any of our sense-based experience of the world is reliable. The contemporary American philosopher Hilary Putnam asks us to imagine a science-fiction scenario:

‘… imagine that a human being (you can imagine this to be yourself) has been subjected to an operation by an evil scientist. The person’s brain (your brain) has been removed from the body and placed in a vat of nutrients which keeps the brain alive. The nerve endings have been connected to a super-scientific computer which causes the person whose brain it is to have the illusion that everything is perfectly normal. There seem to be people, objects, the sky, etc.; but really, all the person (you) is experiencing is the result of electronic impulses travelling from the computer to the nerve endings.



The computer is so clever that if the person tries to raise his hand, the feedback from the computer will cause him to ‘see’ and ‘feel’ the hand being raised. Moreover, by varying the program, the evil scientist can cause the victim to ‘experience’ (or hallucinate) any situation or environment the evil scientist wishes. He can also obliterate the memory of the brain operation, so that the victim will seem to himself to have always been in this environment. It can even seem to the victim that he is sitting and reading these very words about the amusing but quite absurd supposition that there is an evil scientist who removes people’s brains from their bodies and places them in a vat of nutrients which keep the brains alive. The nerve endings are supposed to be connected to a super-scientific computer which causes the person whose brain it is to have the illusion that ...3

The question is: can you be certain that you are not a brain in a vat?

3 Putnam, Hilary (1981) Reason, Truth and History (Cambridge, Cambridge).



Knowledge Handout 5

Scepticism

Putnam’s ‘brain in a vat’ is thought by many philosophers to lead to scepticism. The sceptic doubts our ability to gain knowledge. In other words, the sceptic doubts our ability to satisfy the justification condition for knowledge.

Scepticism comes in various forms (and in various strengths).

1. Local scepticism is scepticism about some particular type of knowledge claim. For example, the atheist is sceptical about claims to knowledge of God and the divine will. Others are sceptical about claims to have knowledge of the supernatural, or of right and wrong.

2. Some sceptics have claimed that the only thing that we can know is that knowledge is impossible. This is extreme scepticism. More moderate forms of scepticism will merely argue that our ability to know is much less than we may be tempted to think – and that we must treat knowledge claims with caution.

Other Minds

One form of local scepticism is scepticism about other minds. How do you know that other people have minds – that they have an inner mental life which is similar to your own?

In the film ‘Alien’, one of the astronauts is discovered to be an android. He looks just like a normal human being; his behaviour suggests that he experiences the world in the ‘normal’ way, that he feels pain, and happiness, and boredom, remorse, worry … But the appearance is deceptive: he is programmed to behave in just the way that a normal human being behaves – but in fact he is no more capable of feeling pain or pleasure than is the hard disk inside your computer. This leads to the sceptic’s question: how do you know that the person sitting beside you has a mind? Clearly asking them is not enough – so what would be sufficient evidence?



Authority

One of the most common ways in which we answer the ‘how do you know?’ question is by appealing to authority. This is the kind of justification we provide whenever we say something like: ‘well, so-and-so told me – and he is in a position to know’. If Neil Armstrong tells you that walking on the moon is easy, then we can probably say that we know that walking on the moon is easy – because he has done it, and so he’s in a position to know.

There is a problem, though. The Greek scientist Ptolemy (c.90-c.168 AD) was for centuries hailed as an authority on astronomy. Ptolemy stated that the Earth was at the centre of the universe. If anyone had thought to ask ‘how do you know that the Earth is at the centre of the universe?’, then ‘because Ptolemy says so’ would have been thought to be a satisfactory answer – it would have been thought to meet the justification condition. We now know that Ptolemy was wrong. This raises a sceptical problem: how do we know that the people whom we take to be authorities really are authoritative?

The problem of the reliability of authority doesn’t only affect subjects such as astronomy. Much of our knowledge is knowledge from authority. How do you know that Ptolemy really existed? How do you know that he stated that the earth was at the centre of the universe – or that people agreed with him? How do you know that Neil Armstrong really did walk on the surface of the moon? Once you come to think about it, you will likely find that a very large proportion of your ‘knowledge’ relies on authority to meet the justification condition.

Induction

As we have seen, there are grounds for sceptical doubt regarding the reliability of the senses. There also seems to be a limit on the kind of knowledge that we can gain from observation, assuming that it is generally reliable.

If I go to look at the swans in my local park, I can see that they are all white. In fact, I have only ever seen white swans. I might be tempted to conclude from this that all swans are white. In Australia, the swans are black – so that in fact the claim that ‘all swans are white’ is false. This raises a question: how many white swans do I need to see before I can safely conclude that all swans are white? This may seem a trivial point – but science needs universal claims (claims about what is always the case). Astronomers tell us that all planets have elliptical orbits. How do we know that this is the case? Until recently, only nine planets were known to exist – and they have all been observed to have elliptical orbits. Would you accept the claim that ‘all swans are white’ from someone who had seen only nine swans?

The problem of induction can be summarised as follows:

‘Some’ does not entail ‘all’.

The word ‘entail’ refers to a relationship between statements. If one statement entails another, then the truth of the first statement guarantees the truth of the second statement. In other words, it is not possible for the first statement to be true and the second statement false.



Examples of entailment:

x is a triangleentailsx has shape

All men are mortal and Socrates is a manentailsSocrates is mortal

Either Connery is First Minister or McConnell isandConnery is not First MinisterentailsMcConnell is First Minister.

Now we can see why the observation of only a limited number of swans can’t confirm for us that all swans are white.

Swan #1 is whiteSwan #2 is whiteSwan #3 is whiteSwan #4 is whiteSwan #5 is white …does not entailAll swans are white.

Another way of putting this is to say that it does not logically follow from the fact that some swans are white that all swans are white.

One observed black swan can confirm that ‘all swans are white’ is false – but no finite number of observations of white swans can confirm that all swans are white. The more swans we see which are white, the more probable it is that all swans are white, and the more probable it is that the next observed swan will be white. But we never get the kind of certainty that we have in the case of ‘all triangles are three-sided figures’. That statement is a priori, analytic, and necessary.

Note how induction operates with regard to two types of statements which we might want to make:

i. ‘Universal’ statements based on observation – such as ‘all swans are white’.ii. Statements about the future based on observation – such as ‘the next swan observed

will be white’.

The eighteenth century Scottish philosopher David Hume points out a worrying example of a statement about the future which is based on observation, and which cannot be guaranteed to be true:

‘The bread which I formerly ate, nourished me … but does it follow, that other bread must also nourish me at another time …? The consequence seems nowise necessary.’4

4 Hume, David An Enquiry Concerning Human Understanding §4 Part II.



As Hume’s example shows, we go through our everyday lives assuming that the future will resemble the past – that water will quench our thirst and not kill us, that a chair will support our weight if we sit on it, that the world will be outside when we open the curtains in the morning. We couldn’t live without making inductive assumptions like these. But as Hume points out, the observational evidence which we have does not guarantee that any of these claims are in fact true.



Sample Activities

1. Matching Exercise

Read each of the following and write in the box provided ‘P’ for ‘Propositional Knowledge’; ‘H’ for ‘How to … Knowledge’, or ‘A’ for ‘Knowledge by Acquaintance’.

The first two have been done for you.

Answers are on p. 42.

1. I know Inverness A

2. I know that Inverness is the capital of the Highlands P

3. I know how to play this game

4. I know some classical music

5. I know that E = mc2

6. I know how to prove that E = mc2

7. I know the scientist who proved that E=mc2

8. I know that there are three conditions for propositional knowledge

9. I know shorthand

10. We know where you live



2. Interpretation Suggested Answers are on p. 42.

Jones is interested in buying a Ford. He visits a used car dealer, and chooses a Ford Fiesta, priced at £4,000. He pays the dealer in cash, and is handed the keys to the car.

There are two things which Jones does not know:

i. The car dealer is a crook, and the car is stolen. Under Scottish law, he can’t legally transfer ownership of the car to Jones – so that even though he has paid for it, it is not Jones’ car.

ii. While he has been at the car dealer’s, Jones’ elderly aunt has died. She has left her Model T Ford to Jones in her will.

Questions

a) Does Jones believe that he owns a Ford?

b) Is it true that Jones owns a Ford?

c) Does Jones know that he owns a Ford?

d) (i) If you think that the answer to Q(c) is ‘yes’, what is it, in addition to Jones’ believing that he owns a Ford, and its being true that he owns a Ford, which leads you to conclude that he knows that he owns a Ford?

(ii) If you think that the answer to Q(c) is ‘no’, then what question should we ask Jones, in order to demonstrate that he does not know that he owns a Ford?



3. Completion Exercise Suggested Answers are on p. 42.

Fill in the blanks to complete the following statements. The first two have been done for you.

a. A Priori truths are known to be true just by thinking.

b. Knowledge which depends upon experience is known as a posteriori knowledge.

c. It is a ____________ condition for being a father that an individual is a parent.

d. It is a ____________ condition for being a parent that an individual is a father.

e. In the statement ‘tigers have stripes’, the ____________ of the statement is ‘tigers’, and the ____________ is ‘have stripes’.

f. An _____________ statement is one in which the meaning of the statement guarantees its truth.

g. A statement in which the meaning of the statement does not guarantee its truth is known as a ________________ statement.

h. A statement which is _______________ true is one which is true, and not possibly not true.

i. A statement which is _______________ true is one which is true, but could conceivably have been false.

j. To _______ is to form a belief.



4. Revision Crossword (Clues on p. 40 and Solution on p. 41)

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4. The part of a statement that claims some property is possessed by the subject.6. Known as a result of observation.7. Type of statement in which the predicate is contained in the subject.11. If a condition must be met, then it is a ... condition.12. Type of scepticism which denies that we can be certain that other people have

mental lives.13. To arrive at a belief. 16. He doubts that some particular type of knowledge is possible.17. One of the three conditions for knowledge.19. The kind of knowledge that is involved in knowing that.20. The part of a statement which is not the predicate.21. One of the ways of answering the ‘how do you know?’ question.22. To break something down into its component parts.24. True and not possibly not true.25. Type of justification in which we appeal to someone else’s knowledge claims.26. This necessary condition for knowledge is met when we can give a satisfactory

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1. Actually true, but the world could have been such that it is false.2. Known just by thinking – without the use of the senses. 3. Philosopher who employs experience as the source of justification.5. One of the activities of philosophy is to do this to our beliefs.8. The meaning of a word. 9. Putnam asks: could you be this?10. The problem of ... is the problem of knowing whether the future will resemble the

past.14. The study of knowledge.15. Perception which depends on background assumptions is said to be this.18. Type of scepticism which denies that any knowledge is possible.23. Type of statement which can’t be tested for truth merely by considering the meanings

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Suggested Answers

1. Matching Exercise

1(A); 2 (P); 3(H); 4(A); 5(P); 6(H); 7(A); 8(P); 9(H); 10(A).

2. Interpretation

a) Yes he does. If we were to attach a lie detector to Jones and ask him ‘do you own a Ford’, then he would answer ‘yes’, and the machine would register that he was telling (what he took to be) the truth.

b) Yes it is. He owns a Model T Ford.

c) The belief and truth conditions are both satisfied, but not the justification condition. The evidence which Jones takes to be evidence that he owns a Ford is actually evidence that he owns a Ford Fiesta – and, under Scots Law, he does not own a Ford Fiesta.

d) i) Your answer here would need to be that he meets the justification condition – but Jones’ belief that he owns a Ford is only true by an enormous coincidence. Note also that Jones thinks that he knows that he owns a Ford Fiesta. He does not believe that he owns a Model T Ford.

d) ii) A good question to ask would be ‘how do you know?’. This is generally a good question to ask, incidentally. In this case, when we ask the question of Jones we discover that even though he thinks he meets the justification condition, he actually does not.

3. Completion Exercise

a. A Priori; b. a posteriori; c. necessary; d. sufficient; e. subject; predicate; f. analytic; g. synthetic; h. necessarily; i. contingently; j. infer.



Section 2

Option A: Descartes’ Rationalism

Contents Page

Teaching Outline 44



Descartes Handout 1 47– Why is Descartes Important?

Descartes Handout 2 49– The Project and Descartes’ Method

Descartes Handout 3 55– Mistrust of the Senses

Descartes Handout 4 58– The Dreaming Argument

Descartes Handout 5 61– The Evil Genius Argument

Descartes Handout 6 67– The Cogito

Descartes Handout 7 70– God





Teaching Outline

The materials in this part of the pack are for Learning Outcome 2 of the Intermediate 2 Epistemology unit – the Descartes option. The unit builds on knowledge of epistemology which students have gained in their prior study of the ‘What is Knowledge?’ part of the unit.

The revised Intermediate 2 Philosophy syllabus introduces two innovations:

i. Students are now expected to be familiar with the primary text (and there is a specified edition: Descartes (1998) Discourse on Method and Meditations on First Philosophy trans. Donald A. Cress. Hackett (ISBN: 0872204200).

ii. The ‘wax’ example from Meditation 2 has been removed from the syllabus, and the ‘Trademark Argument’ for God’s existence from Meditation 3 is now included.

This part of the pack reflects both of these changes.




Extensive guidance on teaching and learning approaches is provided in the Course Specification, and teachers are referred to these at www.sqa.org.uk

The preceding part of this pack (‘What is Knowledge?’) introduced some simple scenarios as a possible basis for class discussion. These may now be reinforced via discussion of Descartes: both the ways in which his epistemology instantiates the problems encountered in this earlier study, and – where appropriate – his likely responses, in the light of the evidence provided by the text.




Guide to Resources

There is an extensive secondary literature on Descartes which may be useful for teachers and students at Intermediate 2.

For teachers who are preparing to teach Descartes for the first time, the following texts may be especially useful:

Arrington, R.L. (1999) A Companion to the Philosophers. Blackwell.

Cottingham, J. (1993) A Descartes Dictionary. Blackwell.

Nadler, S. (ed.) (2002) A Companion to Early Modern Philosophy. Blackwell.

Williams, B. (1978) Descartes – The Project of Pure Enquiry. Penguin.

Wilson, M.D. (1978) Descartes. Routledge.

Various texts on the History of Philosophy include summaries of Descartes’ Meditations which may with profit be studied by students at this level. One of the most widely read is:

Warburton, N. (1998) Philosophy – The Classics. Routledge.

A highly recommended history of philosophy is

Kenny, A. (1998) A Brief History of Western Philosophy. Blackwell.

A classic history of philosophy text, with detailed synopses of the key texts, is:

O’Connor, D.J. (1964) A Critical History of Western Philosophy. Macmillan.

Finally, a text which discusses Descartes’ epistemology in the context of popular films:

Falzon, C. (2002) Philosophy Goes to the Movies. Routledge.

Some of the videos in the RITE series ‘The Examined Life’ may be useful as the basis for class discussion – especially (1) ‘What is Philosophy?’; (6) ‘What is Real?’; (7) ‘How Do We Encounter the World?’; (10) ‘Does God Exist?’; and (12) ‘Is Reason the Source of Knowledge?’.

Details of these videos can be had from:

Resources In Education LtdCross TreeWalton StreetWalton-in-GordanoClevedonSomerset BS21 7AW

Tel. 01275 344931



Descartes Handout 1

Introduction: Why is Descartes Important?

René Descartes (pronounced ‘day-cart’) was born in 1596, just south of Tours, in the Loire region of France.

Descartes is often referred to as ‘the father of modern philosophy’. This may seem a strange description of a man who was 20 years old when William Shakespeare died. Descartes was critical of the philosophy and science of his day (at this time, philosophy and science are not thought to be different areas of enquiry). This philosophy had remained largely unchanged for two thousand years – being based on the pioneering work of the ancient Greek philosopher Aristotle, who lived in the fourth century BC. In departing from this essentially ‘Aristotelian’ philosophy, Descartes framed the main issues which have dominated Western philosophy (and so epistemology) since.

Descartes was educated, from the ages of 10 to 18, at the Jesuit college of La Flèche; while there he began to think that, with the exception of mathematics, most of the subjects which he was being taught were too uncertain to count as genuine knowledge. Descartes was to go on to be a brilliant mathematician (you may have studied Cartesian coordinates in Maths classes; ‘Cartesius’ is the Latin version of Descartes’ name – and the coordinates are his invention). For our present purposes, what is much more significant is Descartes’ very early conviction that non-mathematical knowledge lacked certainty. Throughout his life, Descartes remained committed to discovering a method for making scientific progress.

Descartes left La Flèche in 1614, and went first to study Law at the University of Poitier, and then to join the Dutch army as an unpaid gentleman soldier (he wanted to travel, and to learn more about ‘the great book of the world’). In 1619, Descartes had a formative experience. While sleeping in what he later described as ‘a stove-heated room’, he had three vivid and prophetic dreams. These dreams gave him a vision of a unification of all knowledge. Descartes’ ambition was now established: he would set out to achieve this unification of all knowledge.

What would a ‘unification of all knowledge’ involve? Descartes is aiming for knowledge of life, the universe and everything – to borrow the title of a Douglas Adams novel. This is what having ‘all knowledge’ will involve. To explain the ‘unity’ part of his ambition, Descartes compared knowledge to a tree.



All of the various fields of knowledge – metaphysics, physics, medicine, ethics – would be parts of the same tree. Just as in a tree, where the leaves depend upon branches, which in turn depend upon the trunk – which depends upon the roots, so Descartes envisaged some areas of knowledge being more fundamental than others (metaphysics would be the roots, he thought).

Descartes’ goal in life is set out in the opening sentence of the text which we study for this unit – Meditations on First Philosophy, which was first published in 1641. In that opening sentence, Descartes declares that the goal of this book is to establish something ‘firm and lasting in the sciences’.



Descartes Handout 2

The Project and Descartes’ Method

The Project

As already noted, in the opening sentence of the Meditations, Descartes sets out his project: his reason for writing the book, and what he hopes to achieve:

Several years have now passed since I first realised how numerous were the false opinions that in my youth I had taken to be true, and thus how doubtful were all those that I had subsequently built upon them. And thus I realised that once in my life I had to raze everything to the ground and begin again from the original foundations, if I wanted to establish anything firm and lasting in the sciences.5

Descartes here refers to an experience which is a common one. As we go through life, we discover that we have been in error about various things – that what we have taken to be justified true beliefs were, in fact, false beliefs. This raises a question: which of the beliefs that I have now, will I later discover to be false?

Note also how Descartes refers to what ‘I had subsequently built upon them’. Recall the ‘tree’ analogy – where one belief is the basis for my having a further belief, or set of beliefs, with the latter beliefs depending on the former one. If the former belief is false, then it will be an inadequate support for those beliefs which depend upon it. This is to be a key thought in Descartes’ epistemology.

5 Cress (trans.) p.59.



Descartes’ approach to the problem of still accepting as true, beliefs which are in fact false, is to get rid of all of his former beliefs, and start again – ‘build anew from the foundation’. This is explained by Descartes using the analogy of a basket of apples:

Suppose [a person] had a basket full of apples and, being worried that some of the apples were rotten, wanted to take out the rotten ones to prevent the rot spreading. How would he proceed? Would he not begin by tipping the whole lot out of the basket? And would not the next step be to cast his eye over each apple in turn, and pick up and put back in the basket only those he saw to be sound, leaving the others? (Replies 7, AT 7:481)

Here the basket = the mind, and the apples = all of my former beliefs. Descartes’ point is that if I merely pick apples out of the basket to check to see whether they are good – and put them back if they are – then I can never be sure that I have actually found what rotten apples there are, as I could easily miss some. The best approach, therefore, is to tip out all of the apples, and return them to the basket only if they were clearly good apples.

In just the same way, those who have never philosophised correctly have various opinions in their minds which they have begun to store up since childhood, and which they therefore have reason to believe may in many cases be false. They then attempt to separate the false beliefs from the others, so as to prevent their contaminating the rest and making the whole lot uncertain. Now the best way they can accomplish this is to reject all their beliefs together in one go, as if they were all uncertain and false. They can then go over each belief in turn and re-adopt only those which they recognize to be true and indubitable. (op.cit.)

Recall Descartes’ project: it is to produce something ‘firm and lasting in the sciences’. Descartes does not doubt that many – perhaps most – of the apples are good. To be certain that he has only good apples in his basket, he must start out by treating all of them – good and bad – as if they were bad. By adopting this approach, he is being really rigorous, and so ensuring that no suspect apples/beliefs are allowed to remain.

It may seem to you at this point that Descartes is being unnecessarily stringent. Is it really necessary that he check all of his former beliefs for truth, as the ‘basket of apples’ analogy suggests? For Descartes this is indeed necessary. At the time that he was writing, there was in Europe a growing school of thought which cast doubt on the possibility of our gaining any reliable knowledge at all. One influential sixteenth century French writer, Michel de Montaigne, had denied our ability to gain knowledge via human enquiry. This is a form of scepticism. One of Descartes’ objectives is to show that such scepticism is not warranted: Meditations on First Philosophy is an anti-sceptical text.

So the opening sentence of the book is very important, in setting out Descartes’ anti-sceptical objective. Aristotle had not succeeded in providing a firm and permanent structure in the sciences – but this, Descartes insists, is no reason for giving up, and turning to scepticism.



The Method

The task which Descartes has set himself is a huge one: he has to check all of his former beliefs – what he has simply accepted until now as being true – for truth or falsity, allowing only the true beliefs into his new ‘structure in the sciences’. Descartes writes the Meditations as if he is keeping a diary (there are six Meditations, written as if they were completed on six consecutive days). Today is the day, he suggests at the beginning of Meditation 1: at last he has some free time on his hands to carry out this enormous epistemological task.

Even though he does have this ‘assured leisure in a peaceable retirement’, Descartes will need a shortcut. The number of his former beliefs will be so great, that the task will be impossible otherwise. Regarding the need for a shortcut, Descartes notes that:

… I will not need to show that all my opinions are false, which is perhaps something I could never accomplish.6

Descartes must also be really rigorous. He must take great care not to accept as true any of his former beliefs which are actually possibly false.

So there are two requirements:

i. a shortcutii. rigour.




Regarding the second of these requirements, Descartes notes that:

… reason now persuades me that I should withhold my assent no less carefully from opinions that are not completely certain and indubitable than I would from those that are patently false.7

To ‘withhold my assent’ means ‘to refuse to accept as true’. ‘Indubitable’ means ‘not able to be doubted’.

If a belief is ‘not completely certain and indubitable’, then there is some possibility that it is false. The word ‘completely’ is important here. If there is any doubt at all – even though this doubt is really far-fetched – then the belief is not completely certain and indubitable.

To say that a belief is certain is to say that we have a belief which is justified, and the justification is 100% reliable – ie. there is no possibility of error. Under these circumstances, the belief will be impossible to doubt – ‘indubitable’.

To say a belief is ‘patently false’ is to say that its falsity is obvious – and we don’t need to think about it to see that it is false. The claim that ‘there are some circular triangles’ is manifestly false: if I believe that it is possible for some object to be both circular and triangular at the same time, then my belief is just absurd.

So in addition to certain beliefs, Descartes has distinguished two further categories of belief:

beliefs which are not completely certain and indubitable.

and

beliefs which are patently false.

In other words:

uncertain beliefs

and

false beliefs.




Now remember what Descartes has just suggested:

I should withhold my assent no less carefully from opinions that are not completely certain and indubitable than I would from those that are patently false.

This is how rigour – the second of our requirements listed above – is going to be achieved. For any belief which he has, Descartes is going to ask the question:

Is this an uncertain belief?

If the answer is ‘yes’ – however slight the doubt – Descartes will, as he has just put it, ‘withhold his assent’. In other words, he will not allow the belief in question to go into the category which really matters: the category of beliefs which are impregnable to serious doubt. It is this category which something ‘firm and lasting in the sciences’ will comprise.

Descartes still has, as we have seen, another requirement. Not only must he be really rigorous – he also needs a shortcut. He recognises this again when he states that to check each individual belief from all of the vast number of beliefs which he has accumulated throughout his life ‘is perhaps something I could never accomplish’. This is to be taken literally, incidentally: the task of checking all of my former beliefs could just never be completed.



What Descartes suggests is that ‘undermining the foundations will cause whatever has been built upon them to crumble of its own accord’, and so ‘I will attack straightaway those principles which supported everything I once believed’.

Think about the best way to demolish a building – such as a block of flats. A very inefficient way to knock down the building would be to take a sledgehammer and knock the building down, brick by brick. How it is actually done is just as Descartes suggests: demolition experts will put dynamite around the foundations of the building; once these have been destroyed, the whole building collapses – and a lot of time is saved. Using dynamite on the foundations is a shortcut to the job of demolition.

Descartes takes beliefs to be like clusters of tall buildings – each set of beliefs resting on its own foundation. So his shortcut will be like the demolition man’s shortcut. What he will do is attack ‘the principles upon which my former beliefs rested’ – the foundations.

If we now go back to our earlier discussion of uncertain beliefs and false beliefs, we can see the question which Descartes will pose: ‘is this foundational belief a belief which is entirely certain and indubitable?’. If not, then it is an uncertain belief – and so it must be treated as if it were a false belief: he must ‘withhold his assent’ from it.



Descartes Handout 3

Mistrust of the Senses

In the third paragraph of Meditation 1, Descartes notes that:

Surely whatever I had admitted until now as most true I received either from the senses or through the senses ...8

This seems to be a common sense claim: you will probably agree that most of the beliefs that you have come to hold have come from the senses, and perhaps particularly from the sense of sight. It seems natural to us to go around the world observing it – and so coming to believe an enormous amount of things about the world. The observation that we have this natural tendency to trust the senses is one which will also be made by empiricist philosophers such as David Hume.

You may well be in agreement with what Descartes has to say here: that all the beliefs that you have until now accepted as being most reliable – most likely to be true beliefs – have been based upon the use of the senses. We tend to say things like: ‘I have seen it with my own eyes’, and to take this to be a reliable answer to the question ‘how do you know?’ – a reliable way of meeting the justification condition which we studied in the last unit.

If we believe that we can gain reliable knowledge of the world through the employment of the senses, then we take the following belief to be foundational:

The senses are reliable.

So if I have the belief that this lemon is bitter, and this belief is based on my having just tasted it, then the belief that my senses are reliable is foundational for my belief that the lemon is bitter. Similarly, if I believe that the cup on my desk is red, and if I would answer the ‘how do you know?’ question by responding that I can see that it is, then I am again assuming that my senses are reliable.

As we have already seen, Descartes’ Method of Doubt involves taking foundational beliefs, and asking whether these are beliefs which are entirely certain and indubitable. So the question which he must now consider is: is my belief that my senses are reliable a belief which is entirely certain and indubitable?

Descartes will give three reasons for thinking that the answer is ‘no’. His first reason involves problems such as optical illusions.

Descartes states that ‘it is sometimes proved to me that these senses are deceptive, and it is wiser not to trust entirely to anything by which we have once been deceived.’

Towards the end of the text – in Meditation 6 – Descartes provides examples of such deceptions:




… many experiences gradually weakened any faith that I had in the senses. Towers that had seemed round from afar occasionally appeared square at close quarters. Very large statues mounted on their pedestals did not seem large to someone looking at them from ground level …9

The senses, in other words, will, on occasion, give us conflicting evidence:

a) The tower is round.b) The tower is square.c) The statue is large.d) The statue is small.

It is not possible for both (a) and (b) to be true; the two statements are inconsistent – as are (c) and (d).

What ought we to conclude from the fact that the senses give us such conflicting – inconsistent – evidence?

Descartes, remember, has to be rigorous – and he has to be seen to be rigorous. If we have a method for gaining knowledge (in this case, using the senses) which ever lets us down, then we can never use it as a way of arriving at absolutely reliable knowledge. There will always be a nagging doubt that it was absolutely reliable when we used it. Suppose that you needed to find something out – and that it was really important to you that you know the truth. Suppose also that one of your friends has sometimes lied to you in the past. Would you rely on that friend when it was so important to you to get to the truth?

If what you needed to know was who had borrowed the CD with your homework on it, and the friend who occasionally lies to you had recently told you that a book which you needed was in the library, knowing that it actually wasn’t in the library, wouldn’t you decide that this person was not guaranteed to be reliable as a source of information on the missing CD’s whereabouts? Now you might think that the library book and the CD are completely separate issues. But the point is: if he was unreliable on that point, then he can’t be guaranteed to be unreliable now.

9 Cress (trans.) p.95



Descartes recognises, though, that the senses seem only sometimes to deceive us – and that we can tell when they are deceiving us, and check:

But perhaps, even though the senses do sometimes deceive us when it is a question of very small and distant things, still there are many other matters concerning which one simply cannot doubt, even though they are derived from the very same senses …10

As examples of sense-based beliefs ‘concerning which one simply cannot doubt’, Descartes gives the fact ‘that I am sitting here next to the fire, wearing my winter dressing gown, that I am holding this sheet of paper in my hands’. This kind of knowledge does not appear to be open to possible doubt – is it?

Descartes considers two possible reasons for taking this knowledge to be open to possible doubt. Firstly, there is the case of the insane. They will not only be deceived by the senses into thinking that round towers are really square; they are also liable to believe that:

… that they are arrayed in purple robes when they are naked, or that they have heads made of clay.

Here, what seems to be reliable sense-based experience is not reliable at all. Here the naked madman will believe that his experience of purple clothing is being caused by purple clothing which he is wearing, but he is in error. What is causally responsible for this experience is the ‘unrelenting vapour of black bile’.

Descartes is confident that he is not mad (‘I would appear no less mad, were I to take their behaviour as an example for myself’). Thus it seems that the beliefs earlier alluded to – that I am here, seated by the fire, attired in a dressing gown, having this paper in my hands etc. – are not beliefs which fall into the category of doubtful beliefs, so that I need not withhold my assent from these.

At this point, the philosopher whose career came to be influenced by a dream in a stove-heated room introduces one of the most famous arguments in the history of philosophy.




Descartes Handout 4

The Dreaming Argument

Descartes has identified a set of beliefs – ‘that I am here, seated by the fire, attired in a dressing gown, having this paper in my hands’ etc. – which, it seems, cannot be doubted. If these beliefs cannot be doubted, then they pass the very strict test of the method of doubt, according to which I must withhold my assent from doubtful beliefs just as much as I do from beliefs which are manifestly false. Two possible grounds for doubting these beliefs have been considered:

a. That they are subject to some deception of the senses such as optical illusion.b. That my mind is disturbed by black bile – so that like a lunatic, I am deceived.

The first of these, it seems, may be set aside. Such illusions seem only to affect beliefs about what is hardly perceptible, or very far away – and these beliefs are clearly neither. The second ground is dismissed on the grounds that I am not mad – and that only in that very particular case would I be deceived in beliefs about what is so clearly perceptible and close at hand.

The argument which follows is more far-reaching in its impact than were the brief considerations of optical illusion and insanity. Firstly, it is based on an experience which – unlike madness – all of us share. Secondly, it is an experience which cannot, at the time, be corrected in the way that optical illusions can be corrected. This experience is the experience of dreaming:

This would all be well and good, were I not a man who is accustomed to sleeping at night, and to experiencing in my dreams the very same things, or now and then even less plausible ones, as these insane people do when they are awake. How often does my evening slumber persuade me of such ordinary things as these: that I am here, clothed in my dressing gown, seated next to the fireplace – when in fact I am lying undressed in bed! But right now my eyes are certainly wide awake when I gaze upon this sheet of paper. This head which I am shaking is not heavy with sleep. I extend this hand consciously and deliberately, and I feel it. Such things would not be so distinct for someone who is asleep. As if I did not recall having been deceived on other occasions even by similar thoughts in my dreams! As I consider these matters more carefully, I see so plainly that there are no definitive signs by which to distinguish being awake from being asleep. As a result, I am becoming quite dizzy, and this dizziness nearly convinces me that I am asleep.11

Dreaming is something that affects all human beings – I am a man ‘who is accustomed to sleeping at night, and to experiencing in my dreams the very same things, or now and then even less plausible ones, as these insane people do when they are awake’.

Descartes’ reference here to ‘experiencing in my dreams’ requires emphasis. We need to think of two kinds of experience:

Experiences caused by physical objects

Experiences caused by my dreaming.




In the case of optical illusions, I may recognise the possibility that my senses are deceiving me, and can check to see whether this is in fact the case. But notice how Descartes suggests that ‘there are no definitive signs by which to distinguish being awake from being asleep’. This time, I have no way of checking to see whether my experiences are being caused by physical objects, or caused by my dreaming.

Now, take a statement which is certainly true:

‘It seems to me that there is a piece of paper in front of me.’

How do I know whether this is an experience which is being caused by a physical object – a piece of paper – or an experience which is being caused by my dreaming? It certainly feels like an experience which is being caused by a piece of paper. But note what Descartes says about this: ‘on many occasions I have in sleep been deceived by similar illusions’.

This leads Descartes to the following conclusion:

‘I cannot be certain that I am not now dreaming.’

This is sometimes referred to as ‘the Dream Hypothesis’. If it is true, then I can never be certain that a particular experience is being caused by physical objects, rather than being caused by my dreaming. This in turn means that I can never trust my senses: the objects which they seem to be giving me experience of might not exist at all.

If, as Descartes has earlier suggested, the beliefs which I have until now accepted as most true and certain are based upon the belief that the senses are reliable, then the Dream Argument would appear to render all such beliefs uncertain. If I cannot be certain that I am not now dreaming – and if this is always the case, then I cannot ever be certain that what seems to be the testimony of the senses actually corresponds to reality. I must therefore withhold my assent from all of the beliefs which I have until now accepted as most true and certain.



You may have thought of an objection to Descartes’ Dream Hypothesis. Descartes himself states in the quotation above: ‘what happens in sleep does not appear so clear nor so distinct as does all this’. Surely, you may be thinking, it is true that I mistake dreaming experience for conscious experience when I am asleep and dreaming, but I just don’t make the same mistake when I am awake. Another way of putting this point would be to say that while it is true that ‘there are no certain indications by which we may clearly distinguish wakefulness from sleep’ when we are asleep, there just are these indications – ways of checking – when we are awake.

What are the ways of checking? Well, dreams tend to be largely visual. We don’t tend to have a sense of touch in dreams. Dreams do not have the continuity of waking experience – they are perhaps convincing at the time when we are having them, but they tend to be brief episodes, rather than prolonged experience, as being awake is. Dreams may also have strange elements in them. One of the reasons why you feel relieved (or perhaps disappointed) on waking and finding that you have ‘only been dreaming’ is that dreams can be far removed from reality.

Descartes seems, then, to have made an error. He takes the (true) proposition:

‘I regularly mistakenly take dreaming experience for conscious experience when I am dreaming’

to entail the (false) proposition:

‘I cannot ever tell the difference between dreaming experience and conscious experience’

so that

‘I cannot tell whether I am awake or asleep now.’



Descartes Handout 5

The Evil Genius Argument12

If I cannot achieve anything firm and lasting in the sciences by relying on the senses, I may be able to do so by the use of reason. To arrive at knowledge via reason is to arrive at knowledge just by thinking – without the use of the senses. Even if I have never seen an example of a straight line, I know that a straight line is the shortest distance between two points – and I know this just by thinking about what it is for something to be a straight line. This goes for all straight lines: all of them are the shortest distance between two points.

This is an example of a priori belief. A belief is a priori, if it is arrived at independently of experience – just by thinking.

Note how the Dream Argument does not affect this kind of belief. Even if I am dreaming, it still remains the case that all straight lines are the shortest distance between two points. Similarly, I may be dreaming that there is a rectangular computer screen in front of me – but I am not dreaming that the four angles of a rectangle add up to 360°. Whether I am dreaming or not that belief is surely true.

A Posteriori Belief

There is a rectangular computer screen in front of me.

A Priori Belief

The internal angles of a rectangle add up to 360°.

So grounds for doubting the reliability of the senses are not grounds for doubting the reliability of reason.

12 The term ‘evil genius’ is a translation from the French ‘malin genie’. In French ‘genie’ means ‘genius’, but it also means ‘spirit’ (as in the genie who comes out of Aladdin’s lamp, when he rubs it). Other translations of Descartes’ text refer here to an ‘evil demon’ rather than an ‘evil genius’. The term ‘evil genius’ is a little unfortunate, as it suggests some character in a film, who has a vat full of brains and a big computer with which he gives the brains false impressions of being embodied, while laughing maniacally. It is best to think of an evil spirit, rather than a mad scientist, when thinking of this part of Descartes’ argument.



To see how Descartes finds grounds for doubting the reliability of reason, we need to consider God, as he is traditionally conceived by philosophers.

On the traditional account, God has three properties:

He is omnipotent – ‘all powerful’. There is nothing that God cannot do.

He is omniscient – ‘all knowing’. God is never in doubt, never in error, and never in ignorance.

He is perfectly good.

One way of thinking about what Descartes does next is to imagine a being who had the first two of these properties, but not the third. This being is omnipotent (so can tamper with my thoughts), omniscient (so can read my mind at all times), but is evil rather than perfectly good (so that he will not hesitate to deceive me). This is the ‘Evil Genius’.

Accordingly, I will suppose not a supremely good God, the source of truth, but rather an evil genius, supremely powerful and clever, who has directed his entire effort at deceiving me.13




It is important to stress that Descartes does not believe that there is a evil genius who is doing this. He believes that he cannot prove that such an individual does not exist. This gives us the ‘Evil Genius Hypothesis’:

I cannot be certain that there is no omnipotent and omniscient and evil being who is bent on deceiving me.

Notice what the evil genius can do, if we take as our example a simple piece of reasoning:

1. I ask myself: what is the sum of 3+2?

2. The evil genius – employing his omniscience – is aware that I am trying to work out this sum.

3. He intervenes – using his omnipotence – to make me arrive at the wrong result.

4. I get the answer 6 – which is wrong.

So ordinarily I believe that 3+2=5 – but that is because I trust my powers of reasoning. But if I cannot be certain that there is no evil genius bent on deceiving me, then I cannot be certain that reason is reliable, and so I cannot be certain that 3+2 really does =5.



As before, the Method of Doubt now comes into play:

1. My belief that reason is reliable is put into doubt by the evil genius.

2. As a result of this, I must withhold my assent from my belief that reason is reliable.

3. As a result of this, all a priori beliefs are now open to possible doubt.

4. As a result of this, I must withhold my assent from all a priori beliefs.

Now you may be inclined to respond to this by saying that even if the Evil Genius is only possibly deceiving me, this does not entail that he is deceiving me now (even less does it entail that he is always deceiving me). But remember the point about the friend who sometimes lies to you. If you have no independent way of checking whether he is lying to you now, then you can never be absolutely confident about anything that he tells you – and what Descartes needs is a way of gaining knowledge which he can be 100% confident about.



The evil genius has another important to role to play in Descartes’ philosophy.

Before discussing the evil genius’s impact on the reliability of reason, Descartes asks the question:

…how do I know that he did not bring it about that there is no earth at all, no heavens, no extended thing, no shape, no size, no place, and yet bringing it about that all these things appear to me to exist precisely as they do now?14

What we have here is the introduction of a very radical form of scepticism. Scepticism, recall, is the denial that knowledge is possible.

The Dream Argument has led to a sceptical conclusion: if I cannot be certain that I am not at this moment dreaming, then I cannot be certain that the experience which I have of a coffee cup on my desk is being caused by a coffee cup, and not being caused by a dream. In dreams we may have the experience of visiting places that do not really exist, meeting people who do not really exist, etc. So the Dream Argument leads to the conclusion that I cannot be certain that what I am experiencing at this moment is really happening.

The above quotation from Descartes shows that the Evil Genius Argument leads to a much deeper level of scepticism. When I dream, I dream about cups and desks and buildings and other physical objects. The dream takes these things from the real world – the world outside my mind – and presents me with experiences of things which don’t actually exist, but which are made up from representations of things which do exist (from real desks and buildings and so on).

Now look again at the quotation from Descartes. The Evil Genius Argument (which starts from the claim that I cannot be certain that there is no evil genius) puts in doubt the claim that there is a real world of physical objects at all. The evil genius could cause me to have experiences of a world of physical objects existing in space and time, when there is no such physical reality at all.

Descartes is trying to refute scepticism – he is trying to produce a ‘firm and permanent structure in the sciences’. If he is going to be successful in this, he must prove that there actually is a physical world in space and time – show that there is something to have a science of. Once he has done that, then he can consider the other level of scepticism – the scepticism which claims that the real world may not be exactly as I experience it.

The Virtual Reality Argument

It is interesting to consider how Descartes might have approached the question of how I can be certain that there is a world beyond my mind, had he been writing in the 21st

century, rather than the 17th century.

Our 21st century Descartes might argue like this:




At the same time I must remember that I am living in the 21st century, at a time when virtual reality software can lead to my having amazing experiences. I can fly spacecraft, race stolen cars around Los Angeles, fight in a medieval battle, land a jumbo jet at Heathrow – and all without leaving my own bedroom. I often get so caught up in these virtual reality games that I forget that it is virtual reality. I have often been brought back with a jolt to reality when my mobile phone rings, so realistic has the experience of the game been.

Now here comes the important part:

At this moment it does seem to me that I am experiencing reality, and not virtual reality; what happens in computer games does not appear so clear, or so distinct as does all of this. But how do I know that all of my experience is experience of reality, and not of virtual reality? How do I know that I haven’t been experiencing virtual reality for the whole of my life? In dwelling carefully on this reflection I see so manifestly that there are no certain indications by which we may clearly distinguish reality from virtual reality that I am lost in astonishment. And my astonishment is such that it is almost capable of persuading me that I am now experiencing virtual reality.

If you have seen the film The Matrix – and its two sequels – then you will know that this is exactly what has happened in these films to almost all of the world’s population. They experience a computer-generated dream world – the illusion of a world that no longer exists. The illusion is fed into the brains of these millions of people, who are actually unconscious, in slime-filled cocoons. To them, the virtual world seems to be real. They have the experiences of going to school, watching television (and playing virtual reality computer games), going to football matches, and believing that they are physically doing all of these things, when they aren’t. They are only doing them virtually.

The writers of The Matrix clearly based their film screenplay on books such as Descartes’ Meditations (and Plato’s Republic, which has similar lines of thought).

For the people in their cocoons, there are no certain indications by which they may clearly distinguish reality from virtual reality. Every experience that they have is an experience which is caused by the matrix. So here is the question: how do you know that what you are now experiencing is reality, and not virtual reality?



Descartes Handout 6

The Cogito

We have now reached the end of Meditation 1. It is worth pausing at this point to consider the position which he has reached.

Descartes’ objective is to produce ‘a firm and permanent structure in the sciences’ – in other words, his objective is to show that the sceptics are wrong.

He aims to do this by showing that if we push scepticism as far as we possibly can – treating even slightly doubtful beliefs as if they are absolutely false – we will still nevertheless arrive at knowledge.

At the beginning of Meditation 2 (which is supposed to be Day 2 of his investigation), Descartes seems depressed by the scale of the task which he now faces:

Yesterday’s meditation has thrown me into such doubts that I can no longer ignore them, yet I fail to see how they are to be resolved. It is as if I had suddenly fallen into a deep whirlpool; I am so tossed about that I can neither touch bottom with my foot, nor swim up to the top.15

He repeats the Method of Doubt at this point:

Nevertheless I will work my way up and will once again attempt the same path I entered upon yesterday. I will accomplish this by putting aside everything that admits of the least doubt, as if I had discovered it to be completely false. I will stay on this course until I know something certain, or, if nothing else, until I at least know for certain that nothing is certain.16

Note how he is, it seems, beginning to think that perhaps the sceptics are right after all – that something firm and lasting in the sciences is just not possible, and that ‘nothing is certain’.

Descartes refers to the ancient Greek thinker Archimedes. Archimedes had discovered the principle of leverage: the longer the plank being used, the greater the weight which could be lifted. If he had a long enough plank, and could climb high enough, a man could lift an elephant, using the plank as a lever.

Give me but one firm spot on which to stand, and I will move the earth.(Archimedes (c. 287-212 BC)).

Descartes makes the analogy:

Archimedes sought but one firm and immovable point in order to move the entire earth from one place to another. Just so, great things are also to be hoped for if I succeed in finding just one thing, however slight, that is certain and unshaken.17

15 Cress (trans.) p.63.16 op.cit.17 Cress (trans.) p.63.



If he can find just one belief which escapes the Method of Doubt – one belief which just cannot be doubted – then, Descartes suggests, he can be optimistic that he can use this as a foundation, on which to build his firm and permanent structure in the sciences.

At this point, it occurs to Descartes that there is something that the evil genius cannot do. He cannot deceive me into thinking that I exist, if I do not. In order to be deceived, I have to exist.

Think of the mental states that Descartes has been in so far. A partial list includes:

detecting doubting wishing believing examining imagining.

If I do any of these things – if I undertake any mental process – I must exist in order to do this. I couldn’t, for example, make a wish unless I existed (to say that someone who never existed once made a wish is to say something that just can’t possibly be true). The same goes for trying to detect something, or having a doubt, or having a belief, or examining or imagining. It has to be true that I exist if I do any of these things – and, Descartes, points, out, it can’t be doubted that I have been doing all of these things in Meditation 1.

Descartes has at last found a belief which it is impossible to doubt:

Thus, after everything has been most carefully weighed, it must finally be established that this pronouncement ‘I am, I exist’ is necessarily true every time I utter it or conceive it in my mind.18

In another of his texts – the Discourse on Method of 1637, Descartes makes the point as follows:

I noticed that whilst I thus wished to think all things false, it was absolutely essential that the ‘I’ who thought this should be somewhat,19 and remarking that this truth I think, therefore I am was so certain and so assured that all the most extravagant suppositions brought forward by the sceptics were incapable of shaking it, I came to the conclusion that I could receive it without scruple as the first principle of the Philosophy for which I was seeking.

The phrase ‘I think, therefore I am’ is perhaps the most famous phrase in the history of philosophy. Descartes wrote his texts in Latin and in French. The Latin for ‘I think, therefore I am’ is ‘Cogito ergo sum’ – hence the reference in SQA documents for this course to ‘Descartes’ cogito’. ‘The cogito’ is philosophers’ shorthand for ‘the argument that ‘I think, therefore I am’.

18 Cress (trans.) p.64.19 ie. ‘should exist’; ‘should be something’.



Descartes is suggesting here that what can be known with absolute certainty is ‘I am’ (as he puts the point in the Meditations: ‘I am, I exist’. How do I know that I exist? Because I think. In this argument, ‘I think’ is the premise (a premise in an argument being the evidence which is offered in support of the conclusion), and the conclusion (what the argument is intended to prove) is that ‘I am’.

Descartes’ proposal is that it is not possible for ‘I think’ to be true, and ‘I am’ to be false. We can express this in at least two ways:

1. ‘I think’ entails ‘I am’.2. ‘I think’ is sufficient for ‘I am’.

Notice how Descartes believes himself to have seen off his sceptical opponent: even ‘the most extravagant suppositions’ which the sceptic may bring forward cannot cause me to doubt that I exist.

Note also how Descartes proposes that ‘I exist’ can be taken as a ‘first principle’. Recall his earlier ‘Archimedes’ point; recall also his decision – in Meditation 1 – to ‘build anew from the foundation’. His belief that he exists – a belief which is absolutely ‘certain and assured’ – will be the foundation for Descartes’ ‘firm and permanent structure in the sciences’.



Descartes Handout 7

God

In proving that God exists, Descartes makes use of an assumption which can be expressed as follows:

‘What is more perfect cannot arise from what is less perfect.’

This is usually referred to as the ‘causal adequacy principle’.

Step 1 in this proof comes with something which Descartes finds in his own mind. He has an idea of a perfect being. I am imperfect – because I can get things wrong, and because I can doubt the truth of my beliefs. In order for me to grasp my own imperfection, I must have an idea of a perfect being – so that I can contrast this with my idea of myself.

Descartes believes that this is true for all of us: if we introspect – look inside our own minds – we will discover that we have an idea of a perfect being.

Step 2 employs the assumption that nothing will come of nothing. The idea of a perfect being must have a cause. There must be an answer to the question: ‘how did I come to have this idea?’.

Step 3 employs the causal principle: ‘the more perfect cannot be caused by the less perfect’. If a perfect thing exists, then it must have been caused by a perfect thing.

Step 4 returns to the idea of a perfect being which I find to be in my mind. The idea of a perfect being is a perfect idea. A perfect idea must have a perfect cause. I can’t be the cause of this idea myself, because I am imperfect. So there must exist a perfect being, who placed this idea in my mind.

In the Synopsis of the Meditations, Descartes later gave an example: a very perfect machine. Before the machine is built, the idea of it is in the mind of the engineer who designs it:

For, just as the objective ingeniousness of this idea ought to have some cause (say, the knowledge possessed by the craftsman or by someone else from whom he received this knowledge), so too, the idea of God which is in us must have God himself as its cause.20

At the end of Meditation 3, Descartes compares God to ‘an immense light’ which illuminates ‘my darkened mind’.21

The syllabus refers to ‘clear and distinct perception’. ‘Perception’ must not be taken to mean sensory perception. ‘Perception’ is Descartes’ term for what the mind does when it becomes aware of simple truths.

20 Cress (trans.) p.55.21 Cress (trans.) p.80.



In another of his texts, the Principles of Philosophy, he states: ‘I call a perception clear when it is present and accessible to the attentive mind, just as we say that we see something clearly when it is present to the eye’s gaze and stimulates it with a sufficient degree of strength and accessibility’. Elsewhere he gives examples of clear and distinct ideas: ‘that I exist so long as I am thinking, or that what is done cannot be undone, are examples of truths in respect of which we manifestly possess this kind of certainty. For we cannot doubt them unless we think of them; but we cannot think of them without at the same time believing that they are true’.

Descartes thus derives a ‘truth rule’: ‘whatever I clearly and distinctly perceive is true’.

Once he has this truth rule, Descartes can employ it in order to arrive at his firm and lasting sciences. What is clearly and distinctly known cannot be doubted – and can therefore be put into the category of certain knowledge.

The proof that God exists – that there is a most perfect being – is crucially important. The reason for this is that a perfect being will not be a deceiver. The perfect being, in other words, is not the Evil Genius.

How will the perfect being relate to the Evil Genius? Well, the perfect being must be omnipotent – all-powerful – and so would be able to control the Evil Genius (if he existed). The Evil Genius could not therefore be omnipotent, because he is under the control of God.

God will also be omniscient (he is perfect, therefore he is all knowing). So he would know what the Evil Genius was up to in trying to deceive me.

Because he is perfectly good, God would not allow the Evil Genius to deceive me.

The possibility of there being an Evil Genius can therefore be rejected.

What this does is to restore ‘reason is reliable’ as a foundational belief. God acts as a ‘guarantor’ of all the discoveries of reason – of all the clear and distinct perceptions, such as the cogito, the principle that everything must have a cause, and the causal adequacy principle.

Note what has happened here. Descartes is a rationalist – he aims to arrive at his firm and permanent structure in the sciences using reason: using as a foundation, or first principle, ‘reason is reliable’.

How does Descartes know that reason is reliable? Because God is reliable. Descartes has introduced a further foundation for knowledge – ‘God is reliable’. He has done it in an interesting way: instead of revealing himself through scripture, he reveals himself by leaving his trademark inside me. Once I reflect on that trademark, I come to see that reason is reliable (reason will, after all, be the faculty by which God perceives his own creation – so that in trying to get as close as possible to a God-like understanding, a firm and permanent science, it is appropriate that I use reason).

So Descartes’ rationalism is based on an appeal to God’s benevolence. God is reliable both in that his understanding of everything is reliable, and in that he will not allow me to go wrong – as long as I use my reason carefully. In using my reason carefully, I will trust only clear and distinct perceptions, and the firm and lasting sciences will be firm and permanent because of its comprising only God-guaranteed clear and distinct perceptions.



Sample Activities

1. True or False Test Answers are on p. 76.

The following test is based on Descartes’ First Meditation. State in the space provided whether the statement is true (T) or false (F).

The first two have been completed for you.

1 Descartes was a sceptic. F

2 Descartes employs a sceptical method. T

3The method of doubt involves treating beliefs which are doubtful as if they were true.

4The shortcut which Descartes employs involves applying his method to the foundations for all of his former beliefs.

5Descartes notes that everything that he has so far been most likely to accept as true he has learned a posteriori.

6The foundational belief for all a priori knowledge is ‘the senses are reliable’.

7 Descartes holds that I can be certain that I am not now dreaming.

8The evil genius puts the existence of the external world – the world beyond the mind – in possible doubt.

9The evil genius puts the foundation of a priori knowledge in possible doubt.

10 The foundation of a priori knowledge is the belief that reason is reliable.



2. Interpretation Answers are on p. 76

‘Archimedes sought but one firm and immovable point in order to move the entire earth from one place to another. Just so, great things are also to be hoped for if I succeed in finding just one thing, however slight, that is certain and unshaken.’22

Questions

a. Where in the text does this passage come?

b. What kind of thing will be the ‘firm and immovable point’ for which Descartes is looking?

c. What will make this ‘firm’?

d. What ‘great things’ may be hoped for, if such a ‘firm and immovable point’ is found, according to Descartes?

e. What is the firm and immovable point which he goes on to discover in this part of the text?

f. Does it do the job which Descartes here hopes for?




3. Reading Questions

Read Ch5 of Warburton’s Philosophy – The Classics, and answer the following questions as you read.

1. What is the objective of Descartes’ meditations?

2. What two intellectual forces was Descartes struggling against?

3. What does the method of doubt involve?

4. Does Descartes think this method should inform our day-to-day living?

5. What two possible outcomes could the method of doubt yield?

6. Why does 2+3=5 escape the dreaming argument?

7. Why is the demon hypothesis similar to a virtual reality machine? (N.B. the ‘Evil Genius hypothesis is also known as the ‘Demon’ hypothesis).

8. Why can Descartes be described as ‘trying to beat the sceptics at their own game’?

9. What does the fact that we think we are ‘standing on the station platform at Sidcup’ demonstrate?

10. What Meditations do the Ontological Argument and the Trademark argument appear in?

11. According to Descartes, what method must we resort to if we want understand what the world is really like?

12. How does Descartes distinguish dreams from reality in the 6th Meditation?

13. What two things does Descartes not doubt?

14. What assumption does the Cogito arguably make?

15. Why is Descartes sometimes accused of circularity?

16. Give one criticism of the Trademark argument.



4. Video Exercise

These questions are based on RITE video No 12: ‘Is Reason the Source of Knowledge?’.

Watch the video carefully, and answer the following questions as you watch.

1. What subject was Descartes’ special strength?

2. What recent scientific discovery seemed to support the idea that the Rationalists were right?

3. What subject in particular did Descartes want all his knowledge to be like?

4. Why Does Descartes’ observation of wax support Rationalism?

5. What sort of truths did Rationalists believe that knowledge would reveal?

6. Why did Rationalists think that science supports Theology?

7. Who first came up with the theory of innate ideas?

8. Why did early philosophers think that maths was innate?

9. Apart from maths, what other knowledge did Descartes think was innate?

10. What part of Descartes’ theory did Locke accept and which parts did he reject?

11. How did Leibniz explain the fact that innate ideas are not immediately apparent to us?

12. According to the video, which school of thought appears to have won the day – Rationalism or Empiricism?



Suggested Answers

1. True or False Test

1F; 2T; 3F; 4T; 5T; 6F; 7F; 8T; 9T; 10T

2. Interpretation

a. The passage comes at the beginning of Meditation 2 – shortly after Descartes has employed the Dream and Genius hypotheses, and concluded that all a posteriori beliefs, all a priori beliefs, and the existence of the external world, are all open to possible doubt.

b. It will be a belief.

c. It will be impossible to doubt – so that assent may be granted with confidence.

d. Descartes hopes that this belief may be used as a foundation: a whole structure of beliefs will be based on this belief, and this structure of beliefs will be a firm and lasting scientific account of the world.

e. ‘I am, I exist’. This is often referred to as the ‘cogito’.

f. The cogito gives Descartes only subjective certainty – and he needs objective certainty. For this reason he will later appeal to an innate idea of ‘a most perfect being who made me as I am’.



Section 2

Option B: Humes’ Empiricism

Contents

Teaching Outline 78



Hume Handout 1 81– Why is Hume Important?

Hume Handout 2 83– Impressions and Ideas

Hume Handout 3 90– Simple and Complex Ideas

Hume Handout 4 94– No Innate Ideas

Hume Handout 5 96– The Missing Shade of Blue

Hume Handout 6 102– Hume’s Fork

Hume: Summary of Key Points 109





Teaching Outline

The materials in this part of the pack are for Learning Outcome 2 of the Intermediate 2 Epistemology unit – the Hume option. The unit builds on knowledge of epistemology which students have gained in their prior study of the ‘What is Knowledge?’ part of the unit.




Extensive guidance on teaching and learning approaches is provided in the Course Specification, and teachers are referred to these at www.sqa.org.uk

The preceding part of these materials (‘What is Knowledge?’) introduced some simple scenarios as a possible basis for class discussion. These may now be reinforced via discussion of Hume: both the ways in which his epistemology instantiates the problems encountered in this earlier study, and – where appropriate – his likely responses, in the light of the evidence provided by the text.




Guide to Resources

There is an extensive secondary literature on Hume which may be useful for teachers and students at Intermediate 2.

For teachers who are preparing to teach Hume for the first time, the following texts may be especially useful:

Arrington, R.L. (1999) A Companion to the Philosophers. Blackwell.

Jenkins, J. J. (1992) Understanding Hume. Edinburgh University Press.

Nadler, S. (ed.) (2002) A Companion to Early Modern Philosophy. Blackwell.

Priest, S. (1990) The British Empiricists. Penguin.

The best currently available edition of Hume’s text is published by Oxford University Press:

Hume, D. (1999) An Enquiry Concerning Human Understanding. (ed. Beauchamp, T. L.) Oxford University Press.

Beauchamp provides an extensive introduction, and copious annotations to guide the reader through Hume’s text.

Various texts on the History of Philosophy include summaries of Hume’s Enquiry which may with profit be studied by students at this level. One of the most widely read is:

Warburton, N. (1998) Philosophy – The Classics. Routledge.

A highly recommended history of philosophy is

Kenny, A. (1998) A Brief History of Western Philosophy. Blackwell.

A classic history of philosophy text, with detailed synopses of the key texts, is:

O’Connor, D.J. (1964) A Critical History of Western Philosophy. Macmillan.

Some of the videos in the RITE series ‘The Examined Life’ may be useful as the basis for class discussion – especially (1) ‘What is Philosophy?’; (6) ‘What is Real?’; (7) ‘How Do We Encounter the World?’; (10) ‘Does God Exist?’; and (12) ‘Is Reason the Source of Knowledge?’.

Details of these videos can be had from:

Resources In Education LtdCross TreeWalton StreetWalton-in-GordanoClevedonSomerset BS21 7AW

Tel. 01275 344931



Hume Handout 1

Introduction: Why is Hume Important?

David Hume was born in Edinburgh, probably in the family’s home in the Lawnmarket, on 26 April 1711. He attended Edinburgh University at the very early age of 11, and had completed his first great philosophical work by the time he was 25. Although the main Arts building of Edinburgh University is named David Hume Tower, the university turned Hume down when in 1745 he applied for a job there. The street in which he lived in the final years of his life is named after him: South Saint David Street, which runs from Princes Street to St Andrew Square (the name is a joke; one of the main reasons why Hume was turned down by the university was that he was notoriously sceptical about religion). Hume is buried in Calton cemetery in Edinburgh, and has recently been commemorated by a statue outside the High Court on the Royal Mile. When Hume died, his close friend Adam Smith – who

was also a very eminent philosopher – wrote as his epitaph:

‘Upon the whole, I have always considered him, both in his lifetime and since his death, as approaching as nearly to the idea of a perfectly wise and virtuous man, as perhaps the nature of human frailty will permit’

Hume is an important figure in the Scottish Enlightenment – an intellectual movement in the eighteenth century, based mainly in the universities of Aberdeen, Glasgow and Edinburgh. These Scottish cities were referred to as ‘hotbeds of genius’, where men such as Hume carried out ground-breaking work in philosophy – but also in economics, art, law, architecture, medicine, engineering, and science. The Scottish Enlightenment challenged the beliefs of the past, presenting a new way of understanding human beings and their place in the world. To a great extent, the social sciences were invented at this time. As we shall see, Hume did important work in what comes to called psychology; the Kirkcaldy-born Adam Smith is sometimes referred to as ‘the father of economics’, and Adam Ferguson (who was born in Logierait in Perthshire) did pioneering work in what came to be sociology.

As well as being one of the greatest philosophers, Hume was an eminent historian. He also wrote essays on a wide range of subjects – including government and politics, human nature, aesthetics, economics, and the history of ideas.



The project of the Scottish Enlightenment thinkers is sometimes described as being a ‘Science of Man’. Hume sets out in the text which we are to study – An Enquiry Concerning Human Understanding (1748) – to provide a science of human nature. Hume had earlier stated that his ambition was to be ‘the Newton of the Moral Sciences’. The great English thinker Sir Isaac Newton had, in the previous century, studied natural events such as the motion of the planets and the tides, and had been largely responsible for a new scientific way of understanding the world. Newton had suggested that ‘moral science’ (by which he meant what we would call ‘social science’ – the scientific understanding of man) could be carried out using the same scientific method that Newton had used in carrying out his science. This method – the ‘experimental method’ – is an empiricist method. The starting point for this kind of science is very careful observation. Newton produced laws of gravitation, which described how physical objects behave; this description was based upon very close study of the ways in which these bodies appeared to behave.

Hume’s aim, then, is to discover laws of human perception, desire, feeling, belief, and reasoning.



Hume Handout 2

Impressions and Ideas

We have already seen that knowledge is justified, true belief. An enquiry concerning human understanding will, among other things, investigate how we come to have the beliefs that we do (and will also attempt to answer the question of what beliefs are).

Hume is, therefore, doing what we now call ‘psychology’.

In order to give an account of the functioning of the mind – of the operation of the human understanding – Hume needs first to give an account of the contents of the mind. All of the mind’s processes – sensing, feeling, reasoning, etc. – have to be about something; some content of the thinking is required.

Hume describes all of these mental contents – all of the contents of thinking or feeling – as ‘perceptions’.

If you have studied Psychology, then you will have come across the word ‘perception’ there. In 21st century Psychology, perception is a process – it is the process of the mind’s interpreting the results of sensation, such as the vibrations in the eardrum which cause activity in the auditory nerve in the brain – which is interpreted as a particular sound.

It is important to stress that this is not what Hume means by ‘perceptions’. For Hume a perception is an entity and not a process; it is an item of content in the mind.

Because of the potential for confusion over the word ‘perception’, as Hume uses it, this unit will from now on refer to ‘perception’ in quotation marks, to remind you that it is being used in Hume’s sense, and not in the modern sense.

Hume opens Section 2 of the Enquiries by making an important distinction:

Every one will readily allow, that there is a considerable difference between the perceptions of the mind, when a man feels the pain of excessive heat, or the pleasure of moderate warmth, and when he afterwards recalls to his memory this sensation, or anticipates it by his imagination.

The contrast here is between what is in your mind when, for example, you put your hand into a fire, and what is in your mind when you later remember having done this – or when you merely imagine doing it.

We can try this out for ourselves: imagine, right now, putting your hand in a flame. The experience just is not as unpleasant as actually doing it would be – is it?

The same goes for ‘the pleasure of moderate warmth’. Remembering the pleasure of lying on a beach in the Mediterranean, or imagining it just isn’t the same as actually doing it – actually lying on the beach (if it was, holiday companies would be in big trouble).



So Hume has made a distinction between:

Feeling the pain of heat, or the pleasure of warmth and

Remembering the pain or pleasure, or imagining the pain or pleasure

This is what Hume says about remembering and imagining:

‘These faculties may mimic or copy the perceptions of the senses; but they never can entirely reach the force and vivacity of the original sentiment.’

So we can make various distinctions:

The senses

cause us to have original ‘perceptions’.

The Memory

copies the original ‘perceptions’ of the senses.

The Imagination

mimics the original ‘perceptions’ of the senses.

The senses

cause us to have perceptions which have greater ‘force and vivacity’.

The Memory and Imagination

cause us to have perceptions which have less ‘force and vivacity’.



So Hume is identifying a difference between perceptions in terms of their force and their vivacity.

What is this difference?

Well, consider two points:

If I put my hand into a fire, I don’t need to make any effort to feel the pain – to have a ‘perception’ of the heat and of the pain. I do have to make an effort to remember the pain later, or to imagine the pain.

The remembered or imagined pain and heat will have less of the detail that the original experience would have. No matter how vividly I imagine the pain, I will not be experiencing what I would be experiencing if I actually put my hand in a fire.

So we have more lively and vivacious ‘perceptions’, and less lively and vivacious ‘perceptions’. The less lively and vivacious ones – those which result from the operation of the memory or the imagination – will just never be as lively and vivacious as the ‘perceptions’ of the senses. As Hume puts the point:

‘The utmost we say of them, even when they operate with greatest vigour, is, that they represent their object in so lively a manner, that we could almost say we feel or see it: But, except the mind be disordered by disease or madness, they never can arrive at such a pitch of vivacity, as to render these perceptions altogether undistinguishable.’

A madman may have such a powerful imagination that he mistakes imagined ‘perceptions’ for real ones – screaming in pain as he imagines being burnt – but for the rest of us, the difference between the two types of ‘perception’ is clear. ‘The most lively thought’, Hume suggests, ‘is still inferior to the dullest sensation’.



Hume points out that this applies to every kind of perception. Another example that he gives is of the difference between a man who is feeling anger, and a man who merely imagines being angry.

You can try out Hume’s distinction for yourself.

1. Go over to the window of the room that you are in, and look at the view outside. As you look, there will be ‘perceptions’ in your mind of the various buildings, people, trees, cars, and so on which are outside.

2. After a few moments, stop looking, and go back to your seat. Now call to mind the scene which you have just seen.

3. What is the difference between the ‘perceptions’ in (1), and those in (2)?



There should be two main differences:

1. While it requires no effort at all to have the visual ‘perceptions’ which you have while looking out of the window (and in fact you cannot will yourself not to see what is there), it does require some effort to call to mind the scene – to have the ‘perceptions’ of the buildings, trees, etc., which memory provides.

2. Much of the detail which was present in the visual ‘perception’ is absent in the memory-generated perception.

Hume labels the two ‘perceptions’:

Impressions

are the more lively and vivacious ‘perceptions’ – those which arise from the operations of the senses, or from feeling anger, pain, envy, remorse, etc.

Ideas

are the less lively and vivacious ‘perceptions’ – those which arise either from remembering or from imagining seeing, hearing, tasting, touching, smelling or feeling anger, pain, and so on.



We need to be careful about terminology. An ‘idea’, as Hume uses the term, is what is in the mind whenever I remember something, or imagine something. The idea is the content of that mental operation.

The idea is a less lively and vivacious ‘perception’. In fact, the liveliness and vivacity of an idea in the memory will likely diminish over time. Think of the faces of your school friends on your first ever day at school. The mental image – the idea – is probably fainter, and more difficult to call to mind (and less reliably detailed) than it would have been on the evening of your first day at school, when you went home and remembered all of the people whom you’d seen on that day. So that is what an idea of the memory is: it is a more or less faint copy of what was in your mind during some earlier experience.

What was in your mind during the earlier experience itself is an impression. Why ‘impression’? What Hume may have in mind is something which was common in the eighteenth century, before the development of the modern post office (and before the use of envelopes). When Hume wrote to his friend and fellow philosopher Adam Smith, he had written the letter, and then sealed it. Hume would likely have had his own personal stamp. He would heat a piece of sealing wax, pour it on to the fold on the paper, then put his stamp into the molten wax. This would leave an impression in the wax (which Smith would recognise, on receiving the letter from his friend). The stamp impresses itself in the wax, so that there is now something in the wax which resembles the stamp. Similarly, the world outside the mind impresses itself on the mind when I look at it, or listen to it, etc.



There is one final distinction to make. It may seem unimportant – but it will be a very important distinction in later parts of the Enquiry which are not covered by the Intermediate 2 syllabus.

Hume has identified two different types of impression.

There are impressions such as the impression which I have in my mind when I look at a patch of blue, or taste some red wine, or touch a scrap of velvet, or listen to a passage from Händel, or smell the horse droppings outside in the street. All of these would be familiar impressions to Hume.

There are other impressions which would also be familiar to Hume: the impression in the mind when I feel disappointment at being rejected for a job, or when I feel happiness at being in the company of friends, or when I feel the pain of toothache.

We have, therefore, a distinction between:

Outward Impressions

– impressions which are caused by the operation of one or other of the five senses. These are ‘outward’ in the sense that the world outside the mind is impressing itself on the mind.

Inward Impressions

– impressions caused by feelings such as disappointment or happiness – from the operation of what Hume calls ‘the inward sentiments’.

We would nowadays refer to these as ‘External Impressions’ and ‘Internal Impressions’.



Hume Handout 3

Simple and Complex Ideas

Hume recognises the seemingly limitless power of the human imagination:

‘To form monsters, and join incongruous shapes and appearances, costs the imagination no more trouble than to conceive the most natural and familiar objects. And while the body is confined to one planet, along which it creeps with pain and difficulty; the thought can in an instant transport us into the most distant regions of the universe; or even beyond the universe, into the unbounded chaos, where nature is supposed to lie in total confusion.’

Hume is here alluding to the kind of feats of the imagination which we encounter in 21st

century science fiction. The creators of ‘Dr Who’ provide us with a clear example of how ‘the thought can in an instant transport us into the most distant regions of the universe’.

There is just one limitation which Hume recognises here – one thing which the imagination cannot do:

‘What never was seen, or heard of, may yet be conceived; nor is any thing beyond the power of thought, except what implies an absolute contradiction.’



An ‘absolute contradiction’ arises where we have both a property and its complete opposite. For example, the following two statements are absolutely contradictory:

The object is red The object is not red

If we try to imagine an object that is both completely red and at the same time completely not-red, we can’t do it.

Is this the only restriction on the operation of the imagination? Hume thinks not. If we consider how the imagination operates in creating ideas, we will, he suggests, find a very important further limitation on its operation.

Hume identifies four things which the imagination does – four ways in which it can arrive at its ideas:

But though our thought seems to possess this unbounded liberty, we shall find, upon a nearer examination, that it is really confined within very narrow limits, and that all this creative power of the mind amounts to no more than the faculty of compounding, transposing, augmenting, or diminishing the materials afforded us by the senses and experience.



So the four things that imagination can do are:

1. Compounding. Here the imagination takes two or more ideas from the memory, and puts them together to create a new idea. Hume provides two examples of this:

The Golden Mountain

We have had an impression of a mountain when looking at a mountain, and so have an idea of a mountain in the memory. Similarly, earlier impressions of gold have left an idea of gold in the memory. Imagination can compound these two ideas, arriving at something that I have never actually had an impression of – never seen – a golden mountain.

The Virtuous Horse

I have an idea of a horse in my memory – having earlier had impressions of horses. I have an idea of virtue in my memory – having felt virtuous in the past, or having felt good about witnessing your virtue. The imagination can compound these two ideas, arriving at something which is very remote from my actual experience: a virtuous horse.

2. Transposing. To ‘transpose’ is to change the position of a thing. I can imagine the kinds of monsters which are in science fiction films – or classical literature – by transposing the parts of animals on to human beings.

3. Augmenting. To ‘augment’ is to increase. My imagination has no difficulty in arriving at an idea of a mouse which is the size of a tall building, for example.

4. Diminishing is, of course, the opposite of augmenting. I can easily have the idea of a tiny elephant – or of an elephant with a barely audible ‘trumpet’.



If Hume is right, then we have a complete account of the operation of the imagination.

To see how this account points out an important limitation on the imagination, we need first to reflect on what exactly the imagination is doing.

There are two different kinds of idea:

Simple Ideas

These are ideas in the memory. The memory faithfully copies the earlier impressions.

Simple ideas are less lively and vivacious than are the impressions on which they are based, and simple ideas may fade over time until they vanish altogether.

Complex Ideas

Complex ideas comprise one or more simple ideas, which have been compounded, or transposed, or augmented, or diminished by the imagination.

Complex ideas are, unlike simple ideas, not simple copies of earlier impressions, and they may be very remote indeed from anything which we have ever had an impression of.

Now we can see how the imagination is limited, on Hume’s account: all of the ideas which imagination produces have their origins in the simple ideas of memory. When we ask where these come from, the answer is: from experience. So although at first sight the imagination is almost boundlessly free – being able to imagine anything as long as it is not attempting to imagine something which implies a contradiction – in fact, it is:

… really confined within very narrow limits [because] all this creative power of the mind amounts to no more than the faculty of compounding, transposing, augmenting, or diminishing the materials afforded us by the senses and experience.



Hume Handout 4

No Innate Ideas

Read the following passage from Hume (a translation into more modern English (and more modern examples) is provided on the right):

‘If it happen, from a defect of the organ, that a man is not susceptible of any species of sensation, we always find that he is as little susceptible of the correspondent ideas. A blind man can form no notion of colours; a deaf man of sounds. Restore either of them that sense in which he is deficient; by opening this new inlet for his sensations, you also open an inlet for the ideas; and he finds no difficulty in conceiving these objects. The case is the same, if the object, proper for exciting any sensation, has never been applied to the organ. A Laplander or Negro has no notion of the relish of wine … A man of mild manners can form no idea of inveterate revenge or cruelty; nor can a selfish heart easily conceive the heights of friendship and generosity.’

‘If someone happens to have a defect in one of the senses so that he cannot have a particular type of sensory experience, it will inevitably be found that he also lacks the related ideas. So a blind man has no ideas of the various colours, and a deaf man no idea of different sounds. If the blind man gains sight, or the deaf man hearing, then, because the sensory faculty now functions normally, he will for the first time have the ideas which formerly he lacked. The same thing will happen if the object which causes the outward impression has never been experienced by a man. An observant Muslim will have no idea of the taste of wine. A mild-mannered man has no idea of the feeling of desire for revenge, and a selfish man no idea of love for his fellow man.’

What Hume is suggesting here is that there can be no ideas unless there have earlier been impressions. The man who has been blind from birth will have no idea of the colour blue. The reason for this is, of course, that he has never had an impression of blue. He has never looked at the sky on a clear day, or studied the various shades of blue on the sample cards in a paint shop. Similarly, the Mbuti tribesman in Zaire will have no idea of the taste of Irn Bru; he as never left Zaire, and Irn Bru is not sold there.



During Hume’s lifetime, the Americans, who were rebelling against the British, had a slogan: ‘No taxation without representation’. For Hume, we can suggest a slogan:

No ideas without impressions

All of our ideas come from experience, on Hume’s account. Every idea is either a simple idea – a copy of an earlier impression which is now in the memory – or it is a complex idea, in which case the imagination has created it, using as raw materials the simple ideas stored in the memory. In either case, every single idea has its origin in experience.

If true, this rules out the claim that some ideas are innate. An ‘innate’ idea is one which is in the mind at birth – and so is not the product of experience.

Hume is an empiricist. Empiricism is the doctrine that all of our knowledge comes from experience, and all of our ideas come from experience. Innatism is the doctrine that some of our knowledge is knowledge that we are born with, and some of our ideas are ideas that we are born with.

The truth of the empiricist doctrine entails the falsity of the innatist doctrine. That is to say that if it is true that all knowledge and ideas come from experience (as the empiricists claims), then that guarantees the falsity of the claim that some knowledge and some ideas are present in the mind at birth.

The empiricist’s opponent is the rationalist. Rationalists emphasise the role of reason – unaided by the senses – in giving us knowledge. The rationalists whom Hume opposed tended also to believe in innatism. The French philosopher René Descartes, for example, held that his knowledge of God was innate.



Hume Handout 5

The Missing Shade of Blue

No sooner has Hume emphasised his view that there can be no ideas without impressions, than he appears to contradict himself. There is, he suggests, ‘one contradictory phenomenon, which may prove that it is not absolutely impossible for ideas to arise, independent of their correspondent impressions’. This is the notorious ‘missing shade of blue’ passage. As before, the original is on the left, and a modern translation on the right:

‘Suppose …a person to have enjoyed his sight for thirty years, and to have become perfectly acquainted with colours of all kinds except one particular shade of blue, for instance, which it never has been his fortune to meet with. Let all the different shades of that colour, except that single one, be placed before him, descending gradually from the deepest to the lightest; it is plain that he will perceive a blank, where that shade is wanting, and will be sensible that there is a greater distance in that place between the contiguous colour than in any other. Now I ask, whether it be possible for him, from his own imagination, to supply this deficiency, and raise up to himself the idea of that particular shade, though it had never been conveyed to him by his senses? I believe there are few but will be of opinion that he can …’

‘Suppose that a man aged 30 has had perfect vision all of his life. Suppose also that he has had impressions of colours of all kinds, except for one shade of blue, which he has never seen – and so has never had an impression of. Suppose that all the shades of blue, except for that one, were placed before him in order – from the very darkest navy blue all the way down to the palest of sky blue. It seems clear that he will notice a gap where the missing shade should be; that the gap between the two shades on either side of the missing one is greater than all of the other intervals. The question is, would it be possible for him to gain an idea, from his imagination, of the missing shade of blue, even though it had never been seen by him? I believe that most people will be of the opinion that this would be possible …’

It was suggested earlier that a slogan could be attributed to Hume:

No ideas without impressions

Yet here he is providing us with a ‘contradictory phenomenon’ – a case of just that: an idea without an earlier impression.



Hume responds to this counter-example by dismissing it:

… this may serve as a proof that the simple ideas are not always, in every instance, derived from the correspondent impressions; though this instance is so singular, that it is scarcely worth our observing, and does not merit that for it alone we should alter our general maxim.

In other words, Hume is claiming:

1. This is a proof that we can after all have ideas without impressions, but2. This case is a one-off, and so3. It isn’t really necessary to take up too much time dealing with it, and 4. It certainly is not necessary that I should withdraw my earlier claim that there can be

no ideas without impressions.

One 20th century commentator, H.A. Pritchard, commented in his book Knowledge and Perception, published in 1950, that:

… this is, of course, just the kind of fact which should have led Hume to revise his whole theory. It is really effrontery on his part … to ignore an instance so dead against a fundamental doctrine of his own.

It seems clear that the case of the missing shade of blue is not a one-off: if by some chance the man had heard every note on a piano during his life, except for one, then again his imagination could ‘supply the deficiency’.



The missing shade of blue appears to be a problem because it appears to falsify Hume’s empiricist theory.

Empiricism was defined earlier as the doctrine that all of our knowledge comes from experience, and all of our ideas come from experience.

We can set this out as follows:

If empiricism is true, then there can be no idea which has not come from experience.

The empiricist’s opponent – the innatist – will respond that there are ideas which do not come from experience (innate ideas), so that empiricism is false.

Has Hume, with the missing shade of blue, shown the innatist to be right?



One way of redeeming Hume’s position is to ask the question: could a blind man’s imagination ‘supply the deficiency’?

The answer is surely that it could not.

Note how the imagination is being referred to here by Hume:

I ask, whether it be possible for him, from his own imagination, to supply this deficiency, and raise up to himself the idea of that particular shade, though it had never been conveyed to him by his senses? I believe there are few but will be of opinion that he can …

The reference to the imagination is important. Remember that Hume has listed four operations of the imagination:

1. Compounding.2. Transposing.3. Augmenting.4. Diminishing.

This is why the blind man cannot arrive at an idea of the missing shade. There is nothing which he has experienced which he can compound/transpose/augment/diminish in order to gain the idea of the missing shade – because he has never seen any colours at all. The man in Hume’s passage has seen every shade of blue, except for the missing one. At this point, you should be able to work out for yourself how this man succeeds in ‘raising up to himself the idea of that particular shade, though it had never been conveyed to him by his senses’.



The process:

1. The man has, at various times, an impression of every shade of blue – except for the missing one.

2. This results in his having an idea of every shade of blue except for that missing shade.

3. Because he has an idea of every other shade, he has an idea of the shade immediately to the right of the missing shade (the slightly darker one), and of the shade immediately to its left (the slightly lighter one).

4. By diminishing the slightly darker one he can arrive at the missing shade – and by augmenting the slightly lighter one, he can arrive at the same idea.

5. So from his experience of the other shades, he arrives at the idea of the missing shade.

So while it is true that neither this man nor the blind man has had experience of the missing shade, and also true that our man’s imagination can ‘supply the deficiency’, this does not show that we can have ideas in the absence of experience (if the blind man could have an idea of the missing shade of blue, then that would pose a big problem for Hume).

So what does the ‘missing shade of blue’ demonstrate?

Think about this before turning the page. What is the difference between the idea which the man has of the other shades of blue, and the idea which he has of the missing shade?



What it shows is that colour ideas may be simple ideas, or they may be complex ideas. Because the idea of the missing shade is arrived at through the operation of the imagination – augmenting and diminishing the neighbouring, simple, ideas – it is a complex idea. If the man had actually seen the missing shade, then the idea of it would be a simple idea – an idea in the memory which faithfully copies an earlier impression.

So the missing shade of blue seems only to show that it is not the case that simple ideas and complex ideas form mutually exclusive classes. For at least some ideas, the same idea can be either simple or complex. Suppose the man later on sees the missing shade of blue – gets an impression of it. At that point, he gets a simple idea of what he already had a complex idea of.



Hume Handout 6

Hume’s Fork

Up to now we have been concerned with how we come to have ideas – and Hume has given an empiricist account of how this happens. In the next section of the Enquiry, Hume turns his attention to how we come to have knowledge, and again his account is going to be an empiricist one.

To have knowledge is to have justified, true belief.

What is believed is a proposition – such as ‘today is Monday’.Propositions may be true or false (so that the belief that today is Monday is true if – and only if – today is Monday).My true belief that today is Monday is justified if I can provide some evidence in support of my claim that today is Monday.

Propositions are, therefore, very important in epistemology. The target for belief – what is believed – is a proposition. The target for knowledge is propositions which are believed, but are also true and justified.

We have already come across a distinction between beliefs which are a priori (and which, if true and justified, are a priori knowledge), and beliefs which are a posteriori (and which, if true and justified, are a posteriori knowledge).

Hume has his own terminology for this distinction. The a priori he refers to as Relations of Ideas, and the a posteriori he refers to as Matters of Fact.



Relations of Ideas

Hume tells us that a relation of ideas is ‘either intuitively or demonstratively certain’.

Remember that a key question always to ask is: ‘how do you know?’. Hume is here suggesting two ways in which we may come to know some relation of ideas: through intuition, or through demonstration.

The term ‘intuition’ has a particular meaning in philosophy – and this is very different from how it is used by non-philosophers (when, for example, women refer to something which they call ‘female intuition’).

In philosophy, some claim is intuitive if it is self-evidently true. Think about what ‘self-evident’ means: the claim justifies itself. Here are some examples:

1. Anything that has shape has size.2. Either today is Tuesday or it isn’t.3. Nothing can be bigger than itself.4. An object cannot be bigger than all of its parts.

With these propositions, we just have to think about them to see that they are true. We just immediately ‘see it’. This is what intuition is (it comes from a Latin word, intuere, which means a kind of intellectual ‘seeing’). Notice how we don’t have to spend any time wondering whether an object can be bigger than the sum of its parts: the truth of this is grasped immediately.

The statement ‘an object cannot be bigger than all of its parts’ comes from the Greek mathematician Euclid. He called statements such as these ‘axioms’. An axiom is a statement where the truth of the statement is grasped by intuition – we ‘intuit’ its truth.

What does it mean to say that an axiom is self-evident? It means that when we are asked: ‘how do you know?’, the answer which we are liable to give is: ‘just think about it’. We do not need to look for further justifying evidence. Anyone who doubts that an object cannot be bigger than all of its parts either isn’t thinking clearly, or doesn’t really know what is meant by the statement. The meaning of an axiom guarantees its truth.



So some relations of ideas are ‘intuitively certain’. But not all are: some relations of ideas are ‘demonstratively certain’.

What makes some claim – some relation of ideas – demonstratively certain is that we can work out, a priori, that it is true (ie. we can establish its truth just by thinking – without the need for observation).

As Hume points out, Geometry, Algebra and Arithmetic deal in knowledge which, if not intuitively certain, is demonstratively certain.

Some claim is demonstratively certain when it is one which can be worked out using reasoning. An example which may be familiar to you from maths classes is Pythagoras’ theorem: ‘the square on the hypotenuse on a right angled triangle is equal to the sum of the squares of the other two sides’. Pythagoras worked this out a priori. When he was asked ‘how do you know?’, Pythagoras had provided a proof – a piece of reasoning which shows that for any right-angled triangle, it must be the case that the square on the hypotenuse is equal to the sum of the squares of the other two sides. So a theorem is a priori and demonstrative, and an axiom is a priori and intuitive.

Why call them ‘relations of ideas’?

Relations of Ideas are, like matters of fact, statements. Every statement asserts a relationship between two or more ideas.

If we limit ourselves to statements with only two ideas, then we can see how this works:

a. The cat sat on the mat.b. All triangles are three-sided figures.

Statement (a) asserts a relationship between the cat and the mat, while statement (b) asserts a relationship between triangularity and three-sidedness.



Hume suggests that words lack meaning unless they refer to ideas which we can trace to earlier impressions:

When we entertain … any suspicion, that a philosophical term is employed without any meaning or idea … we need but enquire, from what impression is that supposed idea derived? And if it be impossible to assign any, this will serve to confirm our suspicion.

Now if we return to our two statements above, while statement (a) asserts a relationship between the idea of the cat and the idea of the mat, I can only test the statement for truth or falsity (I can only answer the ‘how do you know? question) by checking the world outside of my mind. I have to look at the mat, to see whether the cat really is on it. That makes the statement ‘the cat sat on the mat’ a matter of fact: it is a statement, the truth of which can only be established a posteriori.

Statement (b), on the other hand, requires no such checking of the way the world is. Here the two ideas – triangularity and three-sidedness – are related in such a way that it just has to be the case that anything that is triangular will be three-sided. So a priori reflection on these ideas is all that is needed to establish the truth of the claim. That makes the statement ‘all triangles are three-sided’ a relation of ideas.

Hume later observes, regarding Relations of Ideas, that:

Propositions of this kind are discoverable by the mere operation of thought, without dependence on what is anywhere existent in the universe. Though there never were a circle or triangle in nature, the truths demonstrated by Euclid would for ever retain their certainty and evidence.

Notice how relations of ideas do not depend on how the world happens to be. Even if the world had never existed at all, Pythagoras’ theorem would still be true.

A statement which is true and could not possibly not be true is a necessary truth. The statement ‘no triangular object is circular’ is necessarily true: true, and could not possibly not be true.



Matters of Fact

The distinction between Relations of Ideas and Matters of Fact is usually referred to as Hume’s Fork.

As we have just seen, relations of ideas ‘are discoverable by the mere operation of thought’. As Hume points out, when we come to consider matters of fact, they are ‘not ascertained in the same manner’.

Consider the following two propositions:

(A)

No triangles are circular

(B)

Some road signs in the UK are circular.

Proposition (A) here is a relation of ideas. All that I have to do to ascertain the truth of (A) is to think about it. My idea of a triangle, and my idea of a circle are such that it is just impossible for any object to be both triangular and circular. Proposition (A) is necessarily true.

How do I know that proposition (B) is true? If I am asked ‘how do you know that some road signs in the UK are circular?’, I can’t answer by saying ‘well, you just have to think about it’. Someone who had never been to the UK, and had no knowledge of the traffic system of this country just couldn’t work out a priori that we have some circular traffic signs (if you doubt this, try working out, just by thinking about it, what shape the traffic signs are in Venezuela).

The only way to find out what shape traffic signs are in a particular country is empirically. We need to carry out what Hume calls ‘enquiry’. That is, we need to observe – go and have a look at traffic signs, or ask someone who has done this and is therefore a reliable authority, or check in an authoritative book such as the Highway Code, and so on.



Note how we can tell, just by thinking about it, that Venezuela does not have traffic signs which are both circular and triangular at the same time. That is necessarily the case (it is a relation of ideas).

Note also that if Venezuela does not have circular traffic signs, we can say that it could have had them (contrast: Venezuela could not possibly have signs which were both circular and triangular at the same time).

The way that we put this point is to say that ‘some traffic signs in the UK are circular’ is a proposition which is contingently true.

So matters of fact are a posteriori, and contingent. Relations of Ideas are a priori and necessary.



There is a test for deciding whether any proposition is a relation of ideas or a matter of fact. Hume points out that:

… the contrary of every matter of fact is still possible; because it can never imply a contradiction, and is conceived by the mind with the same facility and distinctness, as if ever so conformable to reality.

What he means by this is that if we take any proposition which is a relation of ideas – such as ‘no triangles are circular’ – the opposite (‘the contrary’) of this proposition is self-contradictory:

‘some triangles are circular’; or‘all triangles are circular’

are propositions which contradict themselves.

Notice how there is also a psychological test. Our minds cannot conceive any object being both triangular and circular at the same time. A triangular circle is just inconceivable.

With matters of fact, by contrast, the contrary is not self-contradictory. If we say:

‘no traffic signs in the UK are circular’

then we say something that is false – but we have not contradicted ourselves. Because it is only contingently true that some UK traffic signs are circular, the world could have been such that no UK traffic signs are circular (that, of course, is why we have to use empirical means – observation – to find out one way or the other).

Note also that when we come to the psychological criterion – the ‘conceivability in the mind’ criterion – it is in fact easy to conceive of a situation in which there are no circular UK traffic signs (where, for example, the Department of Transport redesigns traffic signs, so that there are no longer any circular signs).



Hume: Summary of Key Points

1. Hume was one of a group of eminent thinkers who lived and worked in Scotland in the eighteenth century, as part of what has since come to be called the Scottish Enlightenment.

2. Hume sets out in An Enquiry Concerning Human Understanding to provide a science of human nature. This will involve the examination of human perception, desire, feeling, belief, and reasoning.

3. The starting point for an enquiry into these various workings of the mind is to enquire into the mental contents on which the mind operates when we are believing, feeling, reasoning, etc. Hume describes all of these mental contents – all of the contents of thinking or feeling – as ‘perceptions’.

4. Hume distinguishes between ‘perceptions’ – mental contents – which are more forceful and vivacious, and ‘perceptions’ which are less forceful and vivacious. The more forceful and vivacious ones are ‘impressions’, and the less forceful and vivacious are ‘ideas’. Impressions are what the mind operates on during episodes of looking, hearing, feeling, etc.

5. Ideas are either the copies of earlier impressions (in the memory), or imitations of impressions (produced by the imagination, which ‘mimics’ impressions).

6. Ideas differ from impressions in that (a) while no act of will is required for me to have an impression – impressions are involuntary – I must will myself to have an idea; and (b) ideas will lack the detail and precision of impressions.

7. Impressions may be either ‘outward’ – caused by the operation of one or other of the five senses – or ‘inward’ – caused by ‘sentiments’ or feelings, such as joy or boredom.

8. While memory is passive, and simply stores faded copies of earlier impressions, imagination is active – generating new ideas from the raw material provided by memory. Ideas in memory are ‘simple’ ideas; those produced by the imagination are ‘complex’ ideas.

9. The imagination works by compounding, transposing, augmenting, or diminishing the simple ideas in the memory. In this way, imagination is ultimately limited by what has been experienced (because its resources all originate with impressions; there can be no ideas without earlier impressions).

10. The imagination is also limited in that it cannot generate contradictory ideas (such as circular triangles).



11. The claim that there can be no ideas without earlier impressions also rules out the possibility of innate ideas – ideas which are present to the mind at birth. As an empiricist, Hume is hostile to the claim that the mind comes with ideas already present in it.

12. Having ruled out the possibility of, eg., someone who has never tasted wine (and so had no impression of wine) coming to have an idea of the taste of wine, Hume nevertheless seems to undermine his own position by conceding that someone who has seen every shade of blue except for one would nonetheless have an idea of the missing shade. This concession may be thought to be important: Hume’s innatist opponents need it to be true that there can be ideas without antecedent impressions.

13. Hume dismisses the ‘missing shade of blue’ as ‘so singular, that it is scarcely worth our observing, and does not merit that for it alone we should alter our general maxim’. His critics have not accepted this causal dismissal of the importance of Hume’s own counter-example.

14. Hume’s apparent position is that for the man who has seen every shade of blue except for the missing one, his idea of the missing shade will be a complex idea. This is evident in Hume’s reference to what it is possible for the man’s imagination to achieve in these circumstances. So colour ideas may be either simple or complex.

15. Hume’s account of knowledge is, like his account of the origin of ideas, an empiricist one. Hume begins by distinguishing Relations of Ideas (which are known a priori), and Matters of Fact (which are known a posteriori). This distinction is commonly known as ‘Hume’s Fork’.

16. A relation of ideas is ‘either intuitively or demonstratively certain’. A statement is intuitively certain if it is self-evidently true; it is demonstratively certain if its truth may be established using reasoning alone (without the use of the senses).

17. Whereas in the case of Relations of Ideas, the justification condition is met just by thinking, in the case of Matters of Fact, some observation of the outside world is required.

18. Relations of Ideas are no only discoverable by the mere operation of thought, they are true without dependence on what is anywhere existent in the universe. That is to say that they are necessarily true – they are true, and could not possibly not be true. Matters of Fact, by contrast, are dependent on what is existent in the universe (if the state of the universe were to change, a Matter of Fact might, as a result, change from being true to being false, or vice versa). So Matters of Fact are contingent: if true, they could conceivably have been false, and if false, they could conceivably have been true.



Sample Activities

1. True or False Test Answers are on p. 115.

The following test is based on Hume’s epistemology. State in the space provided whether the statement is true (T) or false (F).

The first two have been completed for you.

1 One of Hume’s aims is to discover how the human mind works. T

2 On Hume’s account, a ‘perception’ is a process in the mind. F

3 Impressions have less forcefulness and vivacity than ideas.

4 If I am feeling happy, then there is an impression in my mind.

5 The imagination can combine any two simple ideas.

6Memory is merely passive, while the imagination is active, on Hume’s account.

7 Hume believes that some ideas are innate.

8Hume believes that we would not be able to have an idea of the missing shade of blue.

9 Hume uses the term ‘Relations of Ideas’ to refer to a priori beliefs.

10 Matters of fact are a posteriori and contingent.



2. Interpretation Answers are on p. 115.

‘Suppose …a person to have enjoyed his sight for thirty years, and to have become perfectly acquainted with colours of all kinds except one particular shade of blue, for instance, which it never has been his fortune to meet with. Let all the different shades of that colour, except that single one, be placed before him, descending gradually from the deepest to the lightest; it is plain that he will perceive a blank, where that shade is wanting, and will be sensible that there is a greater distance in that place between the contiguous colour than in any other. Now I ask, whether it be possible for him, from his own imagination, to supply this deficiency, and raise up to himself the idea of that particular shade, though it had never been conveyed to him by his senses? I believe there are few but will be of opinion that he can …’

Questions

a. How is this passage in the text important?

b. What is the process by which the man will come to have an idea of the shades of blue which he has seen?

c. What is the process by which the man’s mind can ‘supply the deficiency’, and come to have an idea of the missing shade of blue?

d. What does this tell us about the origins of our ideas of colours?

e. How might this passage be thought to make more plausible the claim that we have ‘innate’ ideas?

f. Must Hume conclude from the ‘missing shade of blue’ example that innate ideas are possible?



3. Reading Questions

Read Ch10 of Warburton’s Philosophy – The Classics, and answer the following questions as you read.

1. What is scepticism?

2. How did Hume regard reason?

3. Which of Hume’s books is the Enquiry essentially a rewrite of?

4. What is Hume’s aim in the Enquiry?

5. What are ‘perceptions’ according to Hume?

6. What does Hume mean by the term ‘impressions’?

7. Where do our ‘ideas’ come from?

8. How can we tell the difference between impressions and ideas?

9. According to Hume, how is it possible to imagine a golden mountain even though we’ve never seen one?

10. What arguments does Hume provide for his belief that all knowledge comes from experience? Provide 2.

11. What is the ‘missing shade of blue’ meant to be an example of?

12. What two sorts of knowledge does ‘Hume’s Fork’ distinguish?

13. What does Hume think we should do with philosophy books which fall into neither category of knowledge?

14. Whose philosophy is Hume theory of impressions and ideas based on?

15. How does the ‘missing shade of blue’ undermine Hume’s position?



4. Video Exercise

The following questions are based on the video ‘Does Knowledge Depend on Experience?’ – Video No.13 in the series ‘The Examined Life – An Invitation to Reflect, Reason and Respond’.

Watch the video carefully and answer the following questions as you go along.

1. Which book is described in the video as ‘an Empiricist manifesto’?

2. Why were Locke’s views seen as controversial in his day?

3. Why does Locke’s account of perception ‘distance the mind from the world’?

4. What is Berkeley’s account of external objects?

5. What aspect of Rationalist doctrine did Hume attack?

6. Why does Hume think effects can’t be known a priori?

7. Why is Hume sceptical about the existence of an external world?

8. What ‘controversial’ view does Hilary Putnam put forward in the video?

9. What academic subjects are Empiricists closely allied with?

10. How does Quine think we learn language?

11. What instinct is central to both Hume and Quine’s philosophy?

12. Why do Empiricists support the slogan that ‘The world comes first’?



Suggested Answers

1. True or False Test

1T; 2F; 3F; 4T; 5F; 6T; 7F; 8F; 9T; 10T.

2. Interpretation

a. The passage is important because Hume here presents what appears to be a counterexample, which falsifies his earlier claim that there can be no ideas for which there have not been prior impressions.

b. The man will have had impressions of those shades which he as seen, and copies of these impressions will be lodged in his memory as simple ideas of the shade of blue in question.

c. The imagination – to which Hume alludes – can either ‘augment’ (ie. darken) the lighter shade which is adjacent to the missing shade, or it can ‘diminish’ (lighten) the darker adjacent shade, or it could do both. These are two of the processes which Hume says the imagination performs in creating ideas.

d. This suggests that our colour ideas can be either simple or complex. They will be simple where we have had the prior impression (we have seen the colour/shade), and complex where we have not, but where the mind has been able to ‘supply the deficiency’.

e. At first sight, Hume is saying here that we can have ideas in our minds of things that we have never had experience of – and this is exactly what the innatist claims is the case when, for example, he claims to have an innate idea of God.

f. No. The missing shade of blue is very close to what the man has experienced, and Hume’s account of the operation of the mind provides a naturalistic explanation of the origin of that idea. God, by contrast, is very remote from anything that I have actually experienced – and there seems to be no possibility of a naturalistic explanation of my coming to have that idea, other than by the route suggested by Hume: the imagination creating it out of simple ideas of goodness, powerfulness, and knowledgeability, and augmenting these to an infinite degree.

3. Reading Exercise

1. Warburton defines scepticism (as it applies in the case of Hume), as being the entertaining of ‘philosophical doubts’.

2. Hume regarded reason as being far more limited in its role than most previous philosophers had supposed.

3. The Enquiry is essentially a rewrite of A Treatise of Human Nature.

4. Hume’s aim in the Enquiry is to make the philosophy of the earlier Treatise more accessible.



5. A ‘perception’ is the content of experience – which arise in the mind whenever we see, feel, remember, or imagine.

6. ‘Impressions’ are perceptions involved in sensing or feeling – so these are what are in the mind when we see, feel, love, hate, desire, or will anything.

7. ‘Ideas’ are copies of impressions.

8. Impressions are clearer and more detailed than ideas. Hume puts the point by saying that impressions are more ‘lively’ than ideas.

9. Hume’s account of how is it possible to imagine a golden mountain even though we’ve never seen one depends upon a distinction between ‘simple’ and ‘complex’ ideas. Complex ideas are made up from the raw material of simple ideas. In this case, my impressions of ‘gold’ and ‘mountain’ lead to my having simple ideas of these, and the mind can then merge the two to produce a complex idea of a golden mountain.

10. Hume argues that when we reflect on the matter, we will come to recognise that any of our ideas can be seen to have had their origin in impressions (this may involve breaking up complex ideas into simple ideas which are their components, and then asking where the simple ideas came from). Hume also suggests that there is evidence for the claim that all knowledge comes from experience in the fact that someone who was blind from birth would have no idea of ‘red’.

11. The ‘missing shade of blue’ is said to be an exception to Hume’s principle that all knowledge comes from experience.

12. ‘Hume’s Fork’ distinguishes between knowledge – such as mathematical knowledge – which is arrived at a priori, and knowledge which contains factual claims which can be observed (and so is a posteriori).

13. We should burn them – because they ‘can contain nothing but sophistry and illusion’.

14. Warburton suggests that Hume’s theory is based on Locke’s.

15. The ‘missing shade of blue’ undermines Hume’s position is a possible counterexample to Hume’s view that all of our ideas come from prior impressions, and, Warburton suggests, ‘if taken seriously, presents a greater threat to Hume’s account of the mind than he seems to realise’. Warburton does, however, go on to recognise that ‘he might consider the idea of the missing shade a complex idea’. This response to the criticism is surely suggested in Hume’s question: ‘could his imagination supply the deficiency?’.



4. Video Exercise Suggested Answers

1. John Locke’s An Essay Concerning Human Understanding (1689).

2. Locke’s views were controversial because they were unconventional.

3. Locke’s starting point is the claim that when we perceive the world, what is immediately present to the mind is an image of, for example, a hand – and not the real, physical hand. The senses make copies of what is out there is the world (in this case, when I hold up my hand and look at it, there is a mental copy of the hand which is in my mind).

4. Berkeley thinks that bodies are ideas, or collections of ideas. There is no such thing as material substance (Berkeley is an immaterialist).

5. All knowledge, Hume thinks, must come from experience – so he attacks the belief that reason by itself has the power to know about the world.

6. Hume suggests that we tend to think that we could know the effects of various causes without having any experience at all. The example given is of one billiard ball colliding with another: ‘We fancy, that were we brought on a sudden into this world, we could at first have inferred that one Billiard ball would communicate motion to another upon impulse; and that we needed not to have waited for the event, in order to pronounce with certainty concerning it’. But the effect (the second ball moving in a particular way) is an effect which is totally different from the cause, and so cannot be discovered in the cause just by thinking about the cause. If our mind was a tabula rasa – a blank slate – then any number of effects would be conceivable, so that a priori discovery of the actual effect is impossible.

7. If all that we ever experience is perceptions in our own minds, then we never experience the objects which are assumed to be causally responsible for these perceptions. Hume suggests therefore that when it comes to proving that these physical objects actually exist, ‘here experience is, and must be, entirely silent’.

8. Putnam wants to reject the claim that sensation is something inside us – in what he calls an ‘inner theatre’ of the mind. What he ironically terms a ‘controversial view’ is that we actually experience the external world (and John Searle agrees: when I hold up my hand and look at it, what I see is not an impression of a hand, but rather the hand – the physical object which is my hand).

9. The empiricists are closely aligned with the natural sciences. The empiricists were, like the natural scientists such as Newton, naturalists (ie. they aimed to provide explanations which involved only natural objects and natural processes).

10. Quine is referred to in the video as a ‘twentieth century Hume’, because he is both a naturalist and an empiricist. Young children learn language, Quine suggests, through observation – for example, by observing the behaviour of others when they use language.



11. Induction – which is defined in the video as the instinct to expect regularity in nature, with similar effects following similar causes.

13. By ‘the world comes first’ is meant the claim that all of the data for our theories about the world come from observation of the world – that is the starting point for all theories of the world.



Glossary

A priori Discoverable by reason, without the aid of the senses.

A posteriori Discoverable by the use of the senses.

Analogy Similarity.

Analytic In an analytic statement, the meaning of the statement guarantees its truth (eg. ‘All sisters are female’)

Appeal to God’s benevolence Descartes’ approach of relying on the fact that God is all-knowing and perfectly good – so would not allow me to reason wrongly, as long as I reason carefully.

Augment To increase. This is one of the four operations of the imagination, on Hume’s account.

Authority Recognised expertise.

Axiom A self-evident truth. An axiomatic statement justifies itself (eg. ‘all the points on the circumference of a circle are equidistant from the centre’).

Brain-in-a-vat Hilary Putnam’s thought experiment – in which brains are artificially caused to have the experiences which they would have if they were inside bodies (which they are not).

Cogito Latin for ‘I think’.

Compound Join together. This is one of the four operations of the imagination, on Hume’s account.

Conceptual analysis To analyse is to break down into component parts. To analyse a concept is to work out its necessary and sufficient conditions.

Conclusion What an argument attempts to prove the truth of (see also ‘premise’).

Consistent Two statements are consistent if it is possible for both to be true at the same time. Consistency is a logical relationship.

Contingently true True, but could conceivably have been false (contrast Necessarily true).

Counterexample A particular example which shows that some general claim is false. The statement ‘all Scottish cities are on the East coast’ is shown to be false by the counterexample of Glasgow – which is on the West coast.



Demon An evil supernatural being. Some translations of Descartes’ Meditations translate ‘evil genius’ as ‘evil demon’

Demonstration A proof.

Diminish Reduce. This is one of the four operations of the imagination, on Hume’s account.

Dubitable Capable of being doubted (so that ‘indubitable’ means incapable of being doubted).

Echolocation A sense possessed by bats: a kind of sonar, which allows them to know that physical objects are nearby, even though bats are blind.

Empiricism The view that reliable knowledge can be gained via experience; the justification condition is met by using one or other of the five senses.

Entail Entailment is a relationship between propositions, in which the truth of one proposition guarantees the truth of another proposition (also known as ‘implication’). Entailment is a logical relationship.

Epistemology The branch of philosophy which considers knowledge. What is knowledge? What can we know with certainty – and how?

Evil Genius Descartes’ evil genius would be capable of deceiving me into reasoning wrongly – and into believing that there is a physical world when there is not.

Falsify Show to be false.

Foundational belief Also known as a ‘first principle’ (hence the full title of Descartes’ text). A belief which is self-evident, and from which we can arrive at further beliefs by inference from the foundations.

Hume’s Fork Hume’s distinction between Matters of Fact (which are a posteriori) and Relations of Ideas (which are a priori).

Hypothesis A statement which may be true or false, but we currently do not know whether it is true or false.

Idea In Hume’s text, an idea is a perception – a mental entity, which is the faded remains of an earlier impression.

Imagination In Hume’s text, the imagination is the faculty of the mind which creates complex ideas, by augmenting, diminishing, compounding, or transposing.



Imply Implication is a relationship between propositions, in which the truth of one proposition guarantees the truth of another proposition (also known as ‘entailment’).

Impression In Hume’s text, an impression is a perception – a mental entity, which is either inward (a feeling) or outward (the result of the operation of the senses).

Inconsistency A relationship between statements in which it is impossible for both to be true at the same time (eg. ‘I am in Inverness’ is inconsistent with ‘I am not in Inverness’).

Indubitable Incapable of being doubted.

Induction A type of argument in which a general claim is the conclusion, and a limited number of individual observations comprise the premises.

Infer To move from accepting one belief to accepting another (eg. I infer from my belief that my phone is ringing that someone wants to speak to me).

Inference The process of inferring.

Innate idea An idea which is present in the mind at birth.

Innatism The philosophical position which holds that there are innate ideas.

Introspect To turn the mind in on itself – observing either your own mental content, or the operation of your mind.

Intuition Immediate awareness – where the belief seems self-evidently true, and this can be grasped without the need for a period of deliberation.

Justification To justify is to give a satisfactory answer to the question ‘how do you know?

Knowledge by Acquaintance The kind of knowledge where you are in contact with something which you claim to know (eg. ‘knowing the woman next door’).

Local Scepticism Scepticism is the doubt that knowledge is possible. Local scepticism is scepticism about a particular kind of knowledge claims – eg. the religious sceptic doubts the possibility of knowledge of God.

Matters of Fact One of the two components of Hume’s Fork. A matter of fact is a statement (which may be false) which has to be tested for truth or falsity a posteriori.



Memory In Hume, the memory is a faculty of the mind which stores simple ideas.

Method of Doubt Descartes’ method of ensuring rigour in his knowledge claims by withholding assent from beliefs which are not absolutely certain and indubitable.

Mutually exclusive classes Two classes are mutually exclusive if it is not possible for a thing to be a member of both. For example, the classes of fathers and daughters are mutually exclusive.

Naturalistic explanation Explanation which only appeals to natural entities and processes, making no reference to the supernatural (eg. making no reference to God).

Naturalists Philosophers who employ naturalistic explanation.

Necessarily true True, and not possibly not true (contrast ‘contingently true’).

Necessary condition A condition which must be met (eg. it is a necessary condition for being in Stirling that I be in Scotland).

Omnipotent All powerful. There is nothing that an omnipotent being cannot do.

Omniscient All knowing. An omniscient being is never in doubt, never in error, and never in ignorance.

Other minds The philosophical problem of other minds is the problem of knowing whether other people have mental lives. Can we infer this from their behaviour?

Perception In Hume’s text a perception is a mental item – either an impression or an idea.

Possible worlds One way of determining whether a statement is necessarily true is to ask whether there are possible worlds in which it is false (if not, then it is necessarily true).

Predicate In a sentence the predicate is what is being claimed of the subject. For example, in ‘The cat sat on the mat’, the subject is the cat and what is being predicated of it is that it sat on the mat.

Premise The part of an argument which is intended to defend the conclusion (see also ‘conclusion’).

Proposition A statement.



Propositional knowledge Knowledge that. Propositional knowledge is justified true belief; what is believed is a proposition.

Rationalism The view that reliable knowledge can be gained via reason; the justification condition is met just by thinking.

Relations of Ideas One of the two components of Hume’s Fork. A relation of ideas is a statement which is tested for truth or falsity a priori.

Scepticism Doubt that knowledge is possible (see also Local Scepticism).

Scottish Enlightenment The intellectual movement of the eighteenth century, largely based in the universities of Aberdeen, Edinburgh and Glasgow, which aimed to arrive at a ‘science of man’ by empirical enquiry.

Species-specific Some faculty or experience is species-specific if it is limited to only one species.

Subject See ‘predicate’

Sufficient condition A condition which, if it is met, guarantees that a further condition is met. For example, it is sufficient for my being in Scotland that I am in Stirling (contrast Necessary condition).

Synthetic In a synthetic statement the meaning of the statement does not guarantee its truth (eg. ‘All sisters are irritating’) (Contrast ‘Analytic’).

Tabula rasa Latin for ‘scrubbed tablet’ – or ‘blank slate’. Those who deny that innatism is true claim that the mind is at birth a tabula rasa.

Theorem The conclusion of an a priori argument.

Theory-laden The claim that perception is ‘theory-laden’ is the claim that we (perhaps unwittingly) interpret what we see, in terms of some background assumptions, or ‘theory’.

Trademark argument Descartes’ argument that God has left an innate idea of himself in my mind.

Transpose To change the position of a thing. This is one of the four operations of the imagination, on Hume’s account (eg. I can imagine a unicorn by transposing a horn from another animal on to the nose of a horse).

Tripartite theory of knowledge The theory that knowledge has three components: belief, truth, and justification.



Universal statements Statements which include the word ‘all’ (eg. ‘all men are mortal’).

Virtual reality The generation by computer software of an environment which appears real to the senses. This raises a philosophical problem: how do I know that what I am experiencing is not merely virtual reality?


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