Philosophy 103 Linguistics 103 Yet, still, Even More Introductory Logic: Critical Thinking

Philosophy 103Linguistics 103

Yet, still, Even MoreIntroductory Logic:

Critical ThinkingDr. Robert Barnard

Last Time:

• Informal Fallacies:1) Fallacies of Relevance2) Fallacies of Weak Induction3) Fallicies of Meaning and Ambiguity• Laws of Thought?

Plan for Today

Try to wrap up Laws of Thought

Start: Meaning and Definition

The “Laws of Thought”

1) Identity2) Non-Contradiction3) Excluded Middle

Are They all both General and Necessary?

The Law of Identity“A true statement is true.”

“All A is A.”

“Everything is what it is, and not something else.”

“Everything is self-identical.”

The Law of Non-Contradiction

“ Nothing A is not A” (a form of ‘identity’?)

“No statement is both true and false at the same time.”

“Nothing is both F and not-F at the same time.”

“Opposite qualities are incompatible.”

“Everything F is not not-F.”

The Law of Excluded Middle

“Every statement must be either true or false.”

“If something is F then it is not not-F.”

“Either F or not-F.”

The Laws of Thought…… Are ways of thinking about LOGICAL

CONSISTENCY.

We do not always recognize what logic requires, but we are fairly good at recognizing what is not logically consistent:

- The Square Circle- The Colorless red box- The empty jar full of pennies.

Logic and Psychology

• Where do the laws of thought come from?• Are they generalizations upon experiences?• Could we arrive at their general correctness

without having a variety of experiences?

A problem for the Psychological Account…

Suppose I accept a logical principle or law (e.g. transitivity) [ X is prior to Y, Y is prior to Z, Therefore X is prior to Z].

Suppose you also accept transitivity.

If you and I acquire transitivity based upon our respective experiences, does this guarentee that MY law of transitivity is the same as YOUR law of transitivity?

What about “Addition”?

The laws of thought …

…are not best thought of as scientific laws describing thought.

Instead they are better understood as regulations governing rational thought.

New Topic: Meaning and Definition

Meaning and Definition

The Logical Characteristics of a situation are not determined by language.

How we understand a claim IS determined by language.

Precise Language is required for Precise Thought

Meaning

There are several commonly recognized kinds of linguistic meaning (kinds of significance)

• Cognitive [Conveys Information, Descriptive, Fact Stating, could be true or false]

• Emotive [ Conveys Feeling, might not be fact stating or true/false –Rhetorically useful]

• Normative [Evaluative]

Fact vs. ValueDescriptive claims attempt to give an account of how

the world is. This is Factual Meaning.

Normative claims attempt to give an account of how the world ought to be, or grade the world relative to a scale. This is Normative Meaning.

Issue: Are there Normative Facts?

Ambiguity

When a word, name, or term can be given more than one meaning in a context, then we say that the term is ambiguous in that context.

“I am going to the bank.”“Are you sore?”

Intension and Extension in Meaning

Cognitive Meaning (informational content) is usually analyzed in terms of what we call Extension and Intension .

• Extension tells us what a word or idea or concept picks out.

• Intension tells us what the nature or essence of the concept or idea is. The intension determines the extension

ExtensionThe EXTENSION of a term (or idea or concept)

simply is the set of all objects or cases that are picked out by the term.

• The extension of ‘cat’ is all cats. • The extension of ‘blue’ is all blue objects. • The extension of ‘American States’ is the 50

States.

IntensionThe INTENSION (with an S) of a term (or idea or

concept) is the definition of the term. It is the rule according to which something either is or is not part of the extension of the term.

The INTENSION of ‘human being’ is something like: “bipedal mammal of the genus homo, species sapiens, capable of reason and humor.”

Alternate Vocabulary

The Intension/Extension distinction is sometimes called:

• Sense/Reference• Connotation/Denotation

Names and DescriptionsBoth Proper Names and Descriptive Phrases can

precisely pick out a specific individual or group.

• Sometimes names are names for descriptions, not objects.

• But one individual or group may have more than one name or description.

• Also not every description will be definite enough to pick out a specific target.

Proper Names / Descriptions• Al Gore (name)• Alberto Gonzales (name)• The Attorney General (description)• The former vice-President (description)• The Sultan of Bhutan (description)• The author of The Firm (description)• The Chancellor of the University of Mississippi

(description)• A lawyer from New York (imprecise description)

Different Terms, Same Object The Morning Star vs. The Evening Star (Venus)

Superman vs. Clark Kent (Kal El the Kryptonian)

The victor at Austerlitz vs. the loser at Waterloo(Napoleon)

Mark Twain vs. Samuel Clemens (that guy who wrote Huck Finn)

Some Interesting Cases• Conventional Connotation– When a term has a conventional meaning that

governs its usual interpretation• “White House” (Is there only one?)• “Western” “Rational” “All-American”

(suppressed content/value judgements?)

• Empty Extension– When a term has a well understood intension but

there is no object in the extension• unicorn• Santa Claus• The present King of France

What does a description REALLY say?A description is a useful device for recognizing the

difference between what language expresses (surface meaning) and what is actually said (logical analysis).

“The present king of France is bald.” (Russell 1905)

There is a person. The person in question is the King of France. If the person in question is the King of France, then he is also bald.

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