Benedict de spinoza metaphysics

Benedict de Spinoza: MetaphysicsBaruch (or, in Latin, Benedict) de Spinoza (1632-1677) was one of the most important rationalist philosophers in the early modern period, along with Descartes, Leibniz, andMalebranche.  Spinoza is also the most influential “atheist” in Europe during this period.  “Atheist” at the time meant someone who rejects the traditional Biblical views concerning God and his relation to nature.  In his most important book, titled Ethics Demonstrated in a Geometrical Manner, Spinoza argues for a radically new picture of the universe to rival the traditional Judeo-Christian one.  Using a geometrical method similar to Euclid’s Elements and later Newton’s Principia, he argues that there is no transcendent and personal God, no immortal soul, no free will, and that the universe exists without any ultimate purpose or goal.  Instead, Spinoza argues the whole of the natural world, including human beings, follows one and the same set of natural laws (so, humans are not special), that everything that happens could not have happened differently, that the universe is one inherently active totality (which can be conceived of as either “God” or “Nature”), and that the mind and the body are one and the same thing conceived in two ways.

Spinoza’s Ethics appeared provocative  to his contemporaries.  First, many of them found his arguments clear and compelling.  Spinoza begins Ethics by defining key terms and identifying his assumptions.  Most of these would have seemed commonplace to Spinoza’s contemporaries.  He then derives theorems, which he calls “propositions,”  on the basis of this foundation.  Many of the philosophers and theologians who first read Spinoza’s Ethicsn found these definitions and assumptions unproblematic, but were horrified by the theorems which Spinoza proved on the basis of them.  Second, by all accounts Spinoza was an especially good man who lived a modest and virtuous life. The mere possibility of a “virtuous atheist,” however, severed one of the most popular arguments in favor of traditional Biblical religion: that without it, living a moral life was impossible.

This article examines some fundamental issues of Spinoza’s new “atheistic” metaphysics, and it focuses on three of the most important and difficult aspects of Spinoza’s metaphysics: his theory of substance monism, his theory of attributes, and his theory of conatus.

Table of Contents1. The Formal Structure of the Ethics2. The Basic Metaphysical Picture: Substance, Attributes, and Modes3. Substance Monism

a. Leibniz’s Objection to Spinoza’s Substance Monism Argumentb. Why Does the One Substance Have Modes?2. Attributes

a. Subjectivismb. Objectivismc. Modal Parallelism2. Conatus

a. Conatus and Purposive Actionb. The Conatus Argument2. References and Further Reading

a. Original Languageb. English Translationsc. Historical Studiesd. Philosophical Studies

1. The Formal Structure of the Ethics

The Ethics is broken into five parts:

I. Of GodII. Of the Nature and Origin of the Mind

III. Of the Origin and Nature of the AffectsIV. Of Human Bondage, or the Power of the AffectsV. Of the Power of the Intellect, or of Human Freedom

Part I concerns issues in general metaphysics (the existence of God, free will, the nature of bodies and minds, etc.) Part II concerns two issues related to the mind: (i) what the mind is and how it relates to the body, and (ii) a general theory of knowledge. In Part III, Spinoza presents his theory of emotions (which he calls “affects”) and a fully deterministic human psychology. In Parts IV and V, Spinoza presents his ethical theory.

Each part of the Ethics is broken into definitions of key terms, axioms (assumptions),propositions (theorems proven on the basis of the definitions, axioms, and the previous propositions),demonstrations (proofs), corollaries (where Spinoza often draws attention to other claims which can be proven on the basis of his propositions, but which are not part of his main argument), and scholia (where Spinoza breaks out of his rigorous structure to comment, argue, or restate the demonstrated material in a more easily accessible way.)

To this classic geometrical structure, Spinoza adds three additions to the Ethics. (1) Spinoza ends Parts I and IV with appendices. In these appendices he comments on the previous part, clarifies his position, and adds new arguments. (2) In Part II and after proposition 13, Spinoza interrupts his argument to include a short discussion on physics and the laws of motion. This part of the Ethics is sometimes called the “Physical Digression,” “Physical Interlude,” or the “Short Treatise on Bodies.” (3) At the end of Part III Spinoza includes an organized list of the definition of the affects (emotions) as argued for in Part III.

When citing the Ethics begin with the Part number, then use the following shorthand:

a Axiom

d Definition

l Lemma

post. Postulate

p Proposition

c Corollary

d demonstration

s Scholium

exp. Explanation

For example, to cite the demonstration of the 14th proposition of Part III one would write “3p14d.” A number of minor variations exist. Some authors also put an “E” at the beginning of the citation to stand for “Ethics” to distinguish the Ethics from Spinoza’s other book written in a geometrical manner, thePrinciples of Cartesian Philosophy Demonstrated in a Geometrical Manner (1663). For example, the demonstration of the 14th proposition of Part III is often cited as “E3p14d.” Other scholars mark the part number with Roman numerals, thus citing the proposition as “IIIp14d” or “EIIIp14d.”

So why does Spinoza utilize this cumbersome method of proof in the Ethics? Scholars have given a number of different answers to this question. One common explanation concerns how people

thought about science in this period. In the 17th century, mathematics was the paradigmatic science. It was widely admired for offering conclusive and incontrovertible proofs which no rational person (who understood them) could reject. Many philosophers attempted to replicate Euclid’s success in other areas and so found other sciences as conclusive and demonstrable as mathematical science. For example, Hobbes attempted to organize political concepts “geometrically” in his Leviathan. Descartes also considered the possibility of organizing his entire philosophy geometrically in the Second Replies, though he never made a serious attempt to do so.) Spinoza, however, geometrically reorganized the first two books of Descartes’Principles (along with other original material) in his first published book: Principles of Cartesian Philosophy Demonstrated in a Geometrical Manner (1663).

Other scholars argue that there is a deeper reason for Spinoza’s use of the geometrical method. The goal of the Ethics, Spinoza says, is to prove those things that can “lead us, by the hand, as it were, to the knowledge of the human mind and its highest blessedness” (Preface to Part II). Ethics is supposed to be a philosophical therapy which helps its readers to overcome their passions and superstitions and become more rational. Working through the proofs, Spinoza promotes these goals by forcing us to think carefully, and so promotes the therapeutic aim of his book. For more on the purpose of the geometrical method see Wolfson 1958, I 3-32; Bennett 1988, 16-28; Garrett 2003; Nadler 2006, 35-51.

2. The Basic Metaphysical Picture: Substance, Attributes, and Modes

According to Spinoza, everything that exists is either a substance or a mode (E1a1). A substance is something that needs nothing else in order to exist or be conceived. Substances are independent entities both conceptually and ontologically (E1d3). A mode or property is something that needs a substance in order to exist, and cannot exist without a substance (E1d5). For example, being furry, orange, hungry, angry, etc. are modes that need a substance which is furry, orange, hungry, angry, etc. Hunger and patches of orange color cannot exist floating around on their own, but rather, hunger and patches of orange color need something (namely, a substance) to be hungry and have the orange color. Hunger and colors are, therefore, dependent entities or modes.

According to almost all of Spinoza’s predecessors (including Aristotle and Descartes) there are lots of substances in the universe, each with their own modes or properties. For example, according to Descartes a cat is a substance which has the modes or properties of being furry, orange, soft, etc. (Though some have argued that Descartes cannot actually individuate multiple extended substances. See Curley 1988, 15-19; 141-2 n. 9.) Spinoza, however, rejects this traditional view and argues instead that there is only one substance, called “God” or “Nature.” Cats, dogs, people, rocks, etc. are not substances in Spinoza’s view, but rather, cats, dogs, people, rocks, etc. are just modes or properties of one substance. This one substance is simply people-like in places, rock-like in other places, chair-like in still other places, etc.

One can think of substance as an infinite space. Some regions of this one space are hard and brown (rocks), other regions of space are green, juicy, and soft (plants), while still other regions are furry, orange, and soft (cats), etc. As a cat walks across the room all that happens in Spinoza’s view is that different regions of space become successively furry, orange, and soft (See Bennett 1984: 88-92 for more on space and the extended substance in Spinoza).

This one substance has an infinite number of attributes. An attribute is simply an essence; a “what it is to be” that kind of thing. According to Descartes, every substance has only one attribute: bodies have only the attribute of extension, and minds have only the attribute of thought. Spinoza, however, argues against this claim that the one substance is absolutely infinite and so it must exist in every way that something can exist. Thus, he infers that the one substance must have an infinite number of attributes (E1p9). An attribute, according to Spinoza, is just the essence of substance under some way of conceiving or describing the substance (E1d4). When we consider substance one way, then

we conceive of its essence as extension. When we consider substance another way, then we conceive of its essence as thought. (See Della Rocca 1996a: 164-167.) While substance has an infinite number of different attributes, Spinoza argues that human beings only know about two of them: extension and thought.

3. Substance Monism

The most distinctive aspect of Spinoza’s system is his substance monism; that is, his claim that one infinite substance—God or Nature—is the only substance that exists.  His argument for this monism is his first argument in Part I of the Ethics.  The basic structure of the argument is as follows:

1. Every substance has at least one attribute.  (Premise 1, E1d4)2. Two substances cannot share the same nature or attribute.  (Premise 2, E1p5)3. God has all possible attributes. (Premise 3, Definition of ‘God’, E1d6)4. God exists.  (Premise 4, E1p11)5. Therefore, no other substance other than God can exist.  (From 1-4, E1p14)

That is, there is only one substance (called “God” or “Nature”) which has all possible attributes.  No other substance can exist because if it existed it would have to share an attribute with God, but it is impossible for two different substances to both have the same attribute.  Spinoza defends each of his four assumptions as follows:

The Argument for Premise One (E1d4)

If a substance existed which did not have any attributes, then (by Spinoza’s definition of attribute at E1d4) the substance would not have an essence.  However, according to Spinoza, it makes no sense to claim that something exists which does not have an essence.  Thus, every substance has at least one attribute.  This premise is not particularly controversial.

The Argument for Premise Two (E1p5)

Spinoza’s argument for the second premise (“Two substances cannot share the same nature or attribute”) is much more controversial.  Here Spinoza argues that if two substances share one and the same attribute, then there is no way to tell the two substances apart.  If substance A and substance B both have attribute 1 as their nature, then in virtue of what are there two different substances here?  Why aren’t A and B just one substance?  Since no cause can be given to explain their distinctness, Spinoza infers that they must actually be the same.  Formally, the argument is as follows:

1. Two substances are distinguished from each other either by a difference in attributes or a difference in modes.  (Premise 1)

2. Substance is prior in nature to its modes.  (Premise 2, E1p1)3. If two substances A and B are indistinguishable, then they are identical.  (Premise 3)4. If substances A and B differ only in attributes, then A and B are two different substances with

different natures.  (From 1 and the definition of “attribute.”)5. If substances A and B differ only in modes and share an attribute, and if the modes are put to

one side and the substances are considered in themselves, then the two substances would be indistinguishable.  (From 1, 2)

6. But if substances A and B are indistinguishable, then they are identical. (From 3, 5)7. Thus, no two substances can share a nature or attribute.  (From 4, 6)

The Arguments for Premise Four (E1p11)

In the demonstration of E1p11, Spinoza explicitly provides a number of different proofs for the existence of a substance with infinite attributes (namely, God.)  One proof is a version of the Ontological Argumentalso used by Anselm and Descartes.  Spinoza’s argument is interesting,

however, because he provides a very different reason for claiming that the essence of each substance includes existence.  Spinoza’s Ontological Argument, once unpacked, is as follows:

1. When two things have nothing in common, one cannot be the cause of the other (Premise 1, E1p3).

2. It is impossible for two substances to have the same attribute (or essence) (Premise 2, E1p5).3. Two substances with different attributes have nothing in common (Premise 3,  E1p6d).4. Thus, one substance cannot cause another substance to exist (From 1, 2, 3.  E1p6).5. Either substances are caused to exist by other substances, or they exist by their own nature

(Premise 4, E1p7d).6. Thus, substances must exist by their own nature (that is, the essence of a substance must

involve existence.) (From 4, 5.  E1p7)

This argument differs from the Ontological Arguments offered by Anselm and Descartes in that (i) Spinoza does not infer the existence of God from the claim that our idea of God involves existence and (ii) Spinoza does not assume that existence is a perfection (and so a property).  Spinoza’s argument, therefore, can avoid some of the more common objections to the Ontological proofs as formulated by Descartes and Anselm.  See Earle 1973a and Earle 1973b for a partial defense of Spinoza’s Ontological Argument.

a. Leibniz’s Objection to Spinoza’s Substance Monism Argument

Spinoza’s Argument for Substance Monism is generally deemed a failure by contemporary philosophers.  There are a number of ways to attack the argument.  The most common way is to reject Spinoza’s second premise (E1p5: “That two substances cannot share the same nature or attribute.”)   One of the most popular arguments against this promise was first presented by Leibniz.  Leibniz argued that whereby it might be impossible for two substances to have all of their attributes in common (because then they would be indistinguishable), it may be possible for two substances to share an attribute and yet differ by each having another attribute that is not shared.  For example, one substance may have attributes A and B and another substance has attributes A and C.  The two substances would be distinguishable because each has an attribute the other lacks, but both substances would nevertheless share an attribute.  This objection was first presented by Leibniz to Spinoza himself.  Though Spinoza did not find the objection persuasive, he never offered an explicit reply.  See Della Rocca 2002: 17-22 for a plausible solution on Spinoza’s behalf based upon the conceptual independence of the attributes.

b. Why Does the One Substance Have Modes?

If Spinoza’s Substance Monism Argument were sound, it would prove that the only substance which exists is God or Nature (a substance with an infinite number of attributes).  But why does this one substance have any finite modes (properties)?  Spinoza provides an answer at E1p16.  Here Spinoza argues that “from the necessity of the divine nature there must follow infinitely many things in infinitely many ways (that is, everything which can fall under an infinite intellect)” (E1p16).  Spinoza argues that the greater something is, the greater the number of properties which follow from its nature or essence.  For example, it follows from the nature of a triangle that it has three sides.  Why do triangles have interior angles of 180 degrees?  Because of the kind of things that they are (that is, because of their essence.)

The greater the essence of the thing, the more properties that follow from it.  God’s essence is the greatest possible essence.  Thus, the greatest possible number of properties (that is, an infinite number) must follow from God’s essence or nature.  Thus, an infinite number of finite modes must follow from the essence of God in just the way that certain properties of triangles (having interior angles of 180 degrees, for example) follow from the essence of a triangle.  Because a triangle’s

essence is finite only a finite number of properties follow from it; because God’s essence is infinite an infinite number of properties follow from it.  Human beings, chairs, tables, cats, dogs, trees, etc. are some of the properties that follow from God’s essence or nature.

Spinoza claims that one important consequence of this proof is that modes are properties of substance.  The view that modes are properties of substance has been denied by at least one prominent interpreter of Spinoza (Curley 1988: 31-39).  Curley’s view has, however, proven unpopular (See Carriero 1999; Malamed 2009.)  The dominant interpretation today is that modes are properties of the one substance.

4. Attributes

Spinoza’s theory of the attributes (extension, thought, etc.) is the most original, difficult, and controversial aspect of his metaphysics.  According to Descartes, the attribute of a substance is simply the substance’s essence (Principles I.53.)  Given this definition, Descartes infers that each substance has only one attribute.  Spinoza modifies Descartes’s definition at E1d4 and states that “by attribute I understand what the intellect perceives of a substance as constituting its essence.”  The Latin here is “per attributum intelligo id, quod intellectus de substantia percipit, tanquam ejusdem essentiam constituens.”  Spinoza then claims that the one substance (“God” or “Nature”) has an infinite number of attributes (E1d6.)  A number of scholars have found it hard to understand how one substance could have multiple attributes each one of which is “what the intellect perceives … as constituting its essence.”  Either Spinoza is claiming that the one substance has multiple essences, or that the attributes are not really the essence of the substance but only seem to be.

The interpretive problems with Spinoza’s theory of attributes begin with his definition.  In the definition he uses the word ‘tanquam’ which can be correctly translated into English both as ‘as if’ and as ‘as.’  If ‘tanquam’ is translated as ‘as if’, then that translation suggests that the attributes are not really the essence of substance but only seem to be the essence of substance.  If, however, ‘tanquam’ is translated as ‘as’, then that translation would seem to indicate that each attribute really is the essence of substance.  The problem is then to explain how we can have one substance with more than one essence.  Thus, the first problem with Spinoza’s theory of attributes is to explain the relation between the attributes and the essence of substance.

According to some scholars (often called “subjectivists”) each attribute is not really the essence of substance but merely seems to be.  According to these scholars, substance’s essence is in some way “hidden” from the intellect and “unthinkable.”  All we can know is how the essence of the one substance appears to the intellect (either as extension or as thought.)  According to other scholars (often called “objectivists”) each attribute really is the essence of substance.  The problem is then to explain how one substance can have multiple essences and still remain one substance.

The second problem with Spinoza’s theory of attributes is to explain how the attributes are related to one other.  If each attribute really is the essence of the one substance, then how do they relate to each other?  Are they identical?  Or is each attribute really different from every other attribute?  If they are identical, then why does the intellect distinguish them?  If they are different, then how can one substance have more than one essence?  Some subjectivists (such as Wolfson 1958: 142 ff.) argue that there is really only one attribute which is distinguished wrongly into numerous attributes by the intellect.  Objectivists, on the other hand, argue that there is more than one attribute and that they are really distinct from each other.

In summary, there are two major problems with Spinoza’s theory of attributes:

1. The Attribute-Essence Problem:  How do the attributes relate to the essence of substance?  Are they identical to the essence of substance or distinct?

2. The Attribute-Attribute Problem:  How do the attributes relate to each other?  Are they identical or distinct?

a. Subjectivism

The most influential defense of the “Subjectivist” interpretation of the attributes is presented by Wolfson 1958 Vol. 1: 142-157.  Wolfson argues that

the two attributes appear to the mind as being distinct from each other.  In reality, however, they are one.  For by [E1p10], attributes, like substance, are summa genera (“conceived through itself”.)  The two attributes must therefore be one and identical with substance.  Furthermore, the two attributes have not been acquired by substance after it had been without them, nor are they conceived by the mind one after the other or deduced one from the other.  They have always been in substance together, and are conceived by our mind simultaneously.  Hence, the attributes are only different words expressing the same reality and being of substance (Wolfson 1958 Vol. 1: 156.)

That is, substance has only one essence and that essence is the sum total of all of its attributes.  The attributes are all identical (and also identical with the substance itself).  The attributes are distinguished from one another merely conceptually (“only different words expressing the same reality”), but in reality the attributes are all one and the same.  The essence of substance is therefore the one attribute extension-thought-etc.  This one attribute cannot be thought as it is, but is instead mentally broken into pieces and considered only partially.  Wolfson thus explicitly provides answers to both the Attribute-Essence Problem and to the Attribute-Attribute Problem.  In both cases Wolfson claims that the relation is identity.  Each attribute is identical to every other attribute (in reality, there is only one “super attribute”) and the essence of substance is this one unthinkable “super attribute.”  Wolfson goes further, however, and also argues that substance is identical to this one unthinkable “super attribute.”

A very different theory of attributes, which also goes by the name of “Subjectivism,” is offered by Bennett.  Bennett argues that the attributes do not constitute the essence of substance at all.  Instead the essence of substance is really the infinite series of finite modes.  The attributes merely appear to constitute the essence of substance.  Bennett disagrees with Wolfson in that Bennett believes “that Nature really has extension and thought, which really are distinct from one another, but that they are not really fundamental properties, although they must be perceived as such by any intellect” (Bennett 1984: 147.)  Thus, Bennett’s solution to the Attribute-Essence Problem is to claim that the essence and attributes are distinct.  But he differs from Wolfson in regard to the Attribute-Attribute Problem.  Here Bennett argues that the attributes are not identical (as Wolfson claims.)

One thing to note here is the looseness of the term “Subjectivism.”  Both Bennett and Wolfson are considered “Subjectivists” because they each deny at least one of the following two claims:

i. The attributes are really distinct.ii. The attributes constitute the essence of substance.

Wolfson denies both; Bennett denies only the second.

b. Objectivism

There are significant problems with both Wolfson’s and Bennett’s “Subjectivism.”  The problem is that there is strong textual evidence in favor of the two claims:

i. The attributes are really distinct.ii. The attributes constitute the essence of substance.

The argument in favor of (i) is that Spinoza claims at E1p10d that all intellects can conceive of the attributes as really distinct (that is, one without the help of the other.)  Thus, even the infinite intellect (that is, God’s Mind) must conceive of the attributes as really distinct.   But the infinite intellect understands everything exactly as it is

(E1p32).  Therefore, the attributes must be really distinct.  This argument has persuaded almost all recent scholars that (i) is true.

The argument in favor of (ii) also relies on the infinite intellect.  Spinoza claims at E2p3 that the infinite intellect has an adequate and true idea of God’s essence.  But on both Wolfson’s and Bennett’s subjectivist accounts that is not true.  On Wolfson’s account the infinite intellect cannot have an adequate idea of the one “super attribute” extension-thought-etc.  The infinite intellect can only have an idea of the different fragmented pieces, namely, extension, thought, etc.  On Bennett’s account the essence of substance isn’t even an attribute.  Both scholars have to admit that the infinite intellect does not have an adequate idea of the essence of substance, which contradicts Spinoza’s claim at E2p3.  See Della Rocca 1996a: 157-171 for more on the case against Subjectivism.

If both claims (i) and (ii) are true on Spinoza’s view, then the attributes are really distinct, and yet each one constitutes the essence of substance.  This is a significant problem.  How can there be only one substance if this substance has multiple distinct essences?  Edwin Curley answers this question by claiming both that “the attributes of substance satisfy the definition of substance” (Curley 1988: 29) and that the attributes come together to form one essence because “this particular complex is a complex of very special elements” (Curley 1988: 30.)  The attributes on Curley’s view are a collection of an infinite number of substances that come together in much the same way that numbers come together to form a number line.  The number line is a unity composed of an infinite amount of very special elements.

Thus, Curley’s solution to the Attribute-Essence Problem is to claim that each attribute pertains to the essence of substance.  Concerning the Attribute-Attribute Problem, Curley claims that the attributes are really distinct from each other.  A similar view may also have been held by Gueroult 1968 Vol. 1.  Objectivism is often characterized by three theses:

i. The attributes are really distinct.ii. The attributes constitute the essence of substance.

iii. The attributes are substances.

The third claim, however, has been disputed by some more recent Objectivists.  Della Rocca in his 1996 book Representation and the Mind-Body Problem in Spinoza offers what is currently the most influential objectivist interpretation of Spinoza’s theory of the attributes.  Della Roccca accepts claims (i) and (ii), but rejects the idea that attributes are themselves substances.  Della Rocca’s interpretation centers on the idea of “referential opacity.”  Della Rocca claims that “a context is referentially opaque if the truth value of the sentence resulting from completing the context does depend on which particular term is used to refer to that object” (Della Rocca 1996a, 122.)  That is, the truth value of a particular sentence depends upon how the objects in the sentence are described.  If the description changes, then the truth value of the sentence may change too.  For example, consider the morning star and the evening star.  The following sentence is true:  Bob believes that the morning star rises in the morning.  However, if you replace ‘the morning star’ without another equally correct description of the same object, then the sentence turns out false.   Because Bob does not know that the morning star and evening star are actually the same thing (namely, Venus) the following sentence is false:  Bob believes that the evening star rises in the morning.  Because the truth-value of the sentence depends upon the description of Venus used in the sentence, this context is referentially opaque.

Della Rocca provides the example of a spy.  One may know that there is a spy in the community and even hate this spy, without knowing that the spy is one’s brother.  In this case the truth-value of sentences such as I hate the spy, I believe that the spy is a spy, etc. all depend upon the term used to pick out the spy.  If we replace ‘the spy’ with the term ‘my brother,’ the truth value of these two sentences changes:  I hate my brother, I believe that my brother is a spy.  Because the truth-value changes when the term used to pick out the person changes, these contexts are referentially opaque.

Della Rocca believes that referential opacity is the key to understanding Spinoza’s theory of attributes.  The idea here is to understand that attribute contexts are referentially opaque.  So, the sentence “the essence of substance is thought” and the sentence “the essence of substance is extension” are referentially opaque contexts.  Della Rocca claims that Spinoza’s definition of attribute should be interpreted as saying: “by attribute I understand that which constitutes the essence of a substance under some description or way of conceiving that substance” (Della Rocca 1996a, 166.)  When substance is considered in one way, then the essence of substance is thought; when substance is considered in another way, then the essence of substance is extension.  What the essence of substance is taken to be will depend upon how the substance is being considered.

By arguing that attribute contexts are referentially opaque, Della Rocca believes that he can avoid the central problem of Subjectivism:  the claim that God misunderstands his own essence (contra E2p3).  Thus, though Della Rocca’s view may at first sound like a form of Subjectivism, it avoids the central problem.  The attributes are really distinct on Della Rocca’s interpretation in that each attribute is the essence of substance under some description of that substance: each really distinct description gives one a different essence.  The attributes also constitute the essence of substance on this view, so long as we add the phrase “under some description or way of conceiving of that substance” to the end.  Della Rocca, however, does not have to accept that attributes are themselves substances.  An attribute is not a substance according to this view (contra Curley); an attribute is simply the essence of a substance under some description or way of conceiving of that substance.

c. Modal Parallelism

How one interprets Spinoza’s theory of attributes will significantly affect the rest of his metaphysics.  For example, one of Spinoza’s most important claims is that “the order and connection of ideas is the same as the order and connection of things” (E2p7.)  That is, the order of modes under the attribute of extension is the same as the order of modes under the attribute of thought.   Spinoza explains this idea in an important and controversial scholium.  He claims that

a circle existing in nature and the idea of the existing circle, which is also in God, are one and the same thing, which is explained through different attributes.  Therefore, whether we conceive nature under the attribute of Extension, or under the attribute of Thought, or under any other attribute, we shall find one and the same order, or one and the same connection of causes, i.e., that the same things follow one another (E2p7s.)

The view that one and the same order exists under each of the attributes is called ‘modal parallelism.’  The word ‘parallelism’ is used because not all scholars believe that the relationship between a body and the mind of that body is identity.  How one interprets modal parallelism in Spinoza will depend upon one’s interpretation of Spinoza’s theory of the attributes.  Two of the most developed and influential recent interpretations of Spinoza’s parallelism are Bennett 1984 (who argues that the mind and body are not identical) and Della Rocca 1996a (who argues that the mind and body are identical).

Bennett and others reject the numerical identity interpretation of parallelism on the grounds that it commits Spinoza to a contradiction.  Spinoza claims that there is no causal interaction between minds and bodies at E3p2.  If he then claimed (so the argument goes) that minds and bodies are identical, then he would seemingly be committed to the following contradiction:  if mind M causally interacts with mind N and body 1 is identical with mind M, then it seems as though body 1 must also causally interact with mind N (thus violating Spinoza’s explicit claims at E3p2.)  This argument is presented by both Bennett 1984, 141 and Delahunty 1985, 197 to argue against the identity of minds and bodies in Spinoza.

But Spinoza does say that the mind and the body are “one and the same thing” conceived in two ways (E2p7s).  What could that mean if not that minds and bodies are identical?  Bennett argues that in Spinoza a mind and a body merely share a part (which he calls a “trans-attribute mode”). 

Minds and bodies are not fully identical.  (See Bennett 1984, 141).  One “trans-attribute mode” can combine both with the attribute of thought (creating a mind) and the attribute of extension (creating a body) at the same time.  Thus, my body is a trans-attribute mode combined with the attribute of extension; my mind is that same trans-attribute mode combined with the attribute of thought.  Bennett thus rejects the interpretation of parallelism whereby a body and a mind are one and the same thing.  A body and its parallel mind merely share a part (namely, a trans-attribute mode).

By contrast Della Rocca argues that minds and bodies in Spinoza are fully identical.  Della Rocca argues that the notion of referential opacity (see the Objectivism section above) can allow Spinoza to accept both the identity of minds and bodies without accepting that minds and bodies causally interact.  Della Rocca claims that causal contexts in Spinoza are referentially opaque.  That is, x is the cause of y only under certain descriptions or ways of thinking about x.  It is not the case that the sentence “x causes y” is true under all possible ways of describing or conceiving of x.  For example, “x under a mental descriptioncaused y” can be true while “x under a physical description caused y” is false.  Thus, Della Rocca argues that the claim that minds and bodies are identical does not entail that minds and bodies causally interact because whether x caused y or not depends upon how x is described.  (See Della Rocca 1996a, 118-140, 157-167.)

5. Conatus

In Part III of the Ethics, Spinoza argues that each mode (that is, every physical and mental thing) “strives to persevere in its being” (E3p6.)  The word translated into English as “strives” is the Latin “conatus.”  (“Conatus” is also sometimes translated as “endeavor.”)  From the claim that every mode strives to persevere in its being, Spinoza infers that each mode’s conatus is the actual essence (E3p7.)  That is, what it is to be a cat is just to strive in a certain cat-like way.  What it is to be a desk is for the complex body to strive in a certain desk-like way.  Every thing that exists—every particle, rock, plant, animal, planet, solar system, idea, mind, etc.—is striving to survive.  From the claim that the essence of every mode is its striving to persist Spinoza derives much of his physics, psychology, moral philosophy, and political theory in Parts III, IV, and V of the Ethics.

Despite the importance of Spinoza’s theory of conatus, there are a number of interpretive and philosophical difficulties with it and Spinoza’s argument for it.  First, there is the widely debated issue of whether Spinoza’s theory of conatus should be interpreted teleologically or non-teleologically.  Is each mode trying to survive?  Are modes goal-oriented things?  Or is Spinoza simply claiming that everything that modes do helps them to survive (while not claiming that modes are acting purposively)?

Second, Spinoza’s argument for the theory of conatus (which takes place in Part III of the Ethics from propositions 4 to 6) has been subject to considerable scrutiny and many scholars have argued that it is multiply invalid.  A few recent scholars have, however, attempted to defend Spinoza’s argument for hisconatus theory against the charge of invalidity.  Garrett 2002, for example, provides an influential defense of the validity of the argument.  Likewise, Waller (2009) provides a partial defense of the first third of the argument.

a. Conatus and Purposive Action

Spinoza clearly denies the claim that God or Nature has a purpose or plan for the universe.  The universe simply exists because it could not fail to exist.  God did not make the universe with any predetermined goal or plan in mind; instead the universe simply follows from God’s essence in just the way that the properties of a triangle follow from the essence of the triangle (E1p16, E1p32c1, E1p33).  In the Appendix to Part I of the Ethics Spinoza claims that

[People] find—both in themselves and outside themselves—many means that are very helpful in seeking their own advantage, for example, eyes for seeing, teeth for chewing, plants and animals for food, the sun for light, the sea for supporting fish.  Hence, they consider all natural things as means

to their own advantage.  And knowing that they had found these means, not provided them for themselves, they had reason to believe that there was someone else who had prepared the means for their use … And since they had never heard anything about the temperament of these rules, they had to judge from themselves.  Hence, they maintained that the gods direct all things for the use of men in order to bind men to them and be held by men in the highest honor. … But while they sought to show that Nature does nothing in vain (that is, nothing not of use to men), they seem to have shown only that Nature and the gods are as mad as man.   … Not many words will be required to show that Nature has no end set before it, and that all final causes are nothing but human fictions (Ethics Part I, Appendix.)

The earth does not exist so that we may live on it.  The universe is not designed for the good of human beings.  The universe has no purpose; it simply exists.  These ideas were revolutionary in the seventeenth century and remain controversial even today.

But some scholars (most influentially, Bennett 1984) argue that Spinoza’s rejection of purpose or goals in nature goes much further than a simple rejection of Divine purposes or goals—Bennett argue that Spinoza rejects all purposive or goal directed activities whatsoever, including human purposive action.  The claim that human actions are not purposive or goal-oriented is startling and presents us with a very different theory of what human beings are.

To understand the impact of this claim, consider the following example: if I walk across the room to get a drink of water, we might believe that this activity is purposive or goal-oriented.  I am walking across the room in order to get a glass of water.  My behavior is partly explained in the common sense view by my goal or purpose (that is, getting a drink of water.)  Bennett 1984, 240-251, however, claims that according to Spinoza this explanation of my behavior must be wrong.  According to Bennett’s Spinoza, I do not walk across the room in order to get water.  Rather I walk across the room because my organs were organized in a certain way such that when light strikes my eyes, it moves certain parts of my brain, which in turn moves certain tendons in my legs, which in turn causes my legs to move back and forth in certain ways, carrying my body to the counter, moving my hand toward the water fountain, etc.  That is, my behavior can be fully and completely understood mechanistically, just like a watch.  The springs inside a watch do not move so that the watch may indicate the correct time, rather the clock indicates the correct time because the springs and levers move in a certain way.  Similarly with human beings, they do not walk in order to get to certain places; they get to certain places because they walk.  (When considering a human being under the attribute of thought, Spinoza would claim that certain ideas follow logically from other ideas in just the way that certain effects follow necessarily from certain causes in the physical world.)  In just the way that the universe exists without any purpose or goal, so every action performed by every human similarly is done for no purpose or goal.  We do what we do simply because we could not fail to—our actions simply follow from the organization of our many complex parts.

Bennett’s interpretation of Spinoza as denying all purposive or goal-oriented action is controversial because Spinoza does claim in a number of different places that while the whole of nature has no purpose or ultimate goal, individuals do act purposively.  In the Appendix to Part I, where Spinoza makes his clearest claims against Divine purposes, he also claims that “men act always on account of an end.”  This passage and other similar ones have been a problem for Bennett’s interpretation.  (See Curley 1990 and Bennett 1990 for more on this debate.)

The issue of whether purposive action is possible is important to the interpretation of Spinoza’s theory ofconatus.  Does Spinoza’s theory of conatus entail that every physical thing—every animal, plant, rock, planet, solar system, idea, and mind—acts in order to persevere in its own being?  Is all of nature goal-oriented, even though the whole of nature is not?  Some (including Garrett 1999) think so.  If Garrett is right, then Spinoza’s physical theory may be a lot closer to Aristotle’s than it is to Descartes’.  Spinoza does not seem fully consistent on the point.  In the words of one recent scholar, Spinoza is “having trouble getting the blind efficient causality of the new science and the end-governed efficient causality of human activity into the same frame, so to speak” (Carriero 2005, 146.)  When Spinoza attempts to treat all of nature, including human behavior and emotions, in a

completely deterministic scientific way—as if human beings were just complicated clocks—he struggles to remain consistent.

b. The Conatus Argument

The argument for Spinoza’s claim that everything strives to persevere in its own being is found at the very beginning of Part III of the Ethics.  The argument is usefully summarized by Garrett 2002 as follows:

1. The definition of a thing affirms, and does not deny, the thing’s essence, or it posits the thing’s essence, and does not take it away.

2. While we attend only to the thing itself, and not to external causes, we shall not be able to find anything in it which can destroy it. (from 1)

3. 3p4 – Nothing can be destroyed except through an external cause. (from 2)4. If [things insofar as they can destroy one another] could agree with one another, or be in the

same subject at once, then there could be something in the same subject which could destroy it.5. [That there could be something in the same subject which could destroy it] is absurd. (from 3)6. 3p5 – Things are of a contrary nature, that is, cannot be in the same subject, insofar as one

can destroy the other. (from 4-5)7. 1p25c – Singular things are modes by which God’s attributes are expressed in a certain and

determinate way.8. 1p34 – God’s power is his essence itself.9. Singular things are modes that express, in a certain and determinate way, God’s power, by

which God is and acts. (from 7-8)10. No thing has anything in itself by which it can be destroyed, or which takes its existence

away. (from 3)11. [Each thing] is opposed to everything which can take its existence away. (from 6)12. 3p6 – Each thing, as far as it can by its own power, strives to persevere in its being (from 9-

10).

That is, Spinoza begins by arguing that no thing can destroy itself (E3p4).  He argues for this claim on the basis of the claim that the definition affirms and does not deny the thing’s essence.  From the claim that no thing can destroy itself, Spinoza then infers that no two things which can destroy each other can be parts of the same whole (E3p5.)  From this claim Spinoza infers that each thing must strive to persevere in its own being (E3p6).

There seem to be numerous invalid inferences here.  The first occurs right at the beginning of the argument.  In the first three lines, Spinoza infers that since a definition of something does not contain anything inconsistent with the thing, that a thing contains nothing contrary to its own nature.  But this inference seems invalid.  If we understand a definition to be a statement of a thing’s essence (see E2d2), then it does validly follow that the essence includes nothing inconsistent with itself (if the essence were internally inconsistent, then it could not exist.)  But it does not follow that a thing cannot have certain accidental properties (not mentioned in the definition) which are capable of destroying the thing.  Thus, Spinoza seems to mistakenly infer a claim about the whole thing (both essential and accidental properties) from a premise which merely concerns the essence.  (See Bennett 1984, 234-237; Della Rocca 1996b, 202-206.  For a recent defense of Spinoza’s argument see Waller forthcoming.)

Another invalid inference occurs toward the end of the argument in lines 6 and 11.  Spinoza infers that since two things cannot both be parts of the same whole, they must actively oppose one another.   However, perhaps they could simply be in a passive relation to one another.  It is one thing to passively resist, and it is quite another to actively resist.  (See Garber 1994, 61-63 for more on this objection and its roots in Leibniz.)  A few recent scholars have attempted to respond to these charges on Spinoza’s behalf.  See, for example, Garrett 2002.

Gottfried Leibniz: MetaphysicsThe German rationalist philosopher, Gottfried Wilhelm Leibniz (1646-1716), is one of the great renaissance men of Western thought. He has made significant contributions in several fields spanning the intellectual landscape, including mathematics, physics, logic, ethics, and theology. Unlike many of his contemporaries of the modern period, Leibniz does not have a canonical work that stands as his single, comprehensive piece of philosophy. Instead, in order to understand Leibniz’s entire philosophical system, one must piece it together from his various essays, books, and correspondences. As a result, there are several ways to explicate Leibniz’s philosophy. This article begins with his theory of truth, according to which the nature of truth consists in the connection or inclusion of a predicate in a subject.

Together with several apparently self-evident principles (such as the principle of sufficient reason, the law of contradiction, and the identity of indiscernibles), Leibniz uses his predicate-in-subject theory of truth to develop a remarkable philosophical system that provides an intricate and thorough account of reality. Ultimately, Leibniz’s universe contains only God and non-composite, immaterial, soul-like entities called “monads.” Strictly speaking, space, time, causation, material objects, among other things, are all illusions (at least as normally conceived). However, these illusions are well-founded on and explained by the true nature of the universe at its fundamental level. For example, Leibniz argues that things seem to cause one another because God ordained a pre-established harmony among everything in the universe. Furthermore, as consequences of his metaphysics, Leibniz proposes solutions to several deep philosophical problems, such as the problem of free will, the problem of evil, and the nature of space and time. One thus finds Leibniz developing intriguing arguments for several philosophical positions—including theism, compatibilism, and idealism.

This article is predominately concerned with this broad view of Leibniz’s philosophical system and does not deal with Leibniz’s work on, for example, aesthetics, political philosophy, or (except incidentally) physics. Leibniz’s “mature metaphysical career” spanned over thirty years. During this period, it would be surprising if some of his basic ideas did not change, but, remarkably, the broad outline of his philosophy does remain constant.

Table of Contents1. Life2. The Idea of Truth3. Sufficient Reason4. Substance, Briefly5. Necessary Being6. Problems of Freedom, Sin, and Evil

a. Freedom and Sinb. Problem of Evil2. Space, Time, and Indiscernibles

a. Against the Absolute Theoryb. The Relational Theoryc. Objections and Replies2. Substance as Monad

a. Monads and Complete Conceptsb. Pre-established Harmony, Windowlessness, and Mirroring

2. Implications of Substances as Monads

a. Levels of Realityb. Little Perceptionsc. Composites and Substantial Forms

d. Innate Ideas2. Monadic Activity and Time3. Influence4. Editions of Leibniz

1. Life

Gottfried Wilhelm Leibniz was born in Leipzig, Germany, on July 1, 1646. He was the son of a professor of moral philosophy. After university study in Leipzig and elsewhere, it would have been natural for him to go into academia. Instead, he began a life of professional service to noblemen, primarily the dukes of Hanover (Georg Ludwig became George I of England in 1714, two years before Leibniz’s death). His professional duties were various, such as official historian and legal advisor. Above all, he was required to travel widely, meeting many of the foremost intellectuals in Europe—of particularly formative importance were the astronomer, mathematician, and physicist Huygens, and the philosopher Spinoza.

Leibniz was one of the great polymaths of the modern world. Moreover, a list of his significant contributions is almost as long as the list of his activities. As an engineer, he worked on calculating machines, clocks, and even mining machinery. As a librarian, he more or less invented the modern idea of cataloguing. As a mathematician, he not only produced ground-breaking work in what is now called topology, but came up with the calculus independently of (though a few years later than) Newton, and his notation has become the standard. In logic, he worked on binary systems, among numerous other areas. As a physicist, he made advances in mechanics, specifically the theory of momentum. He also made contributions to linguistics, history, aesthetics, and political theory.

Leibniz’s curiosity and genius ranged widely, but one of the most constant of his concerns was to bring about reconciliation by emphasizing the truths on each side of even the most seemingly contradictory positions. Throughout his life, he hoped that his work on philosophy, as well as his work as a diplomat, would form the basis of a theology capable of reuniting the Church, which had been divided since the Reformation in the 16th Century. Similarly, he was willing to engage with, and borrow ideas from, the materialists as well as the Cartesians, the Aristotelians as well as the most modern scientists. It is quite ironic, then, that he was a partial cause of a dispute between British and Continental mathematicians concerning who was first to develop the calculus (and who might have plagiarized who), a dispute which slowed the advance of mathematics in Europe for over a century.

However, the great variety of Leibniz’s work meant that he completed few of his ambitious projects. For present purposes, this means above all that Leibniz’s rich and complex philosophy has to be gathered primarily from a large set of quite short manuscripts, many fragmentary and unpublished, as well has his various correspondences. (The last section of this article provides bibliographical details of several editions of Leibniz’s work.) As a result, a major controversy in Leibniz scholarship is the question of where to begin. Insofar as Leibniz is a logician, it is tempting to begin with his conception of truth (and, indeed, this will be the starting point of this article). But insofar as Leibniz is a metaphysician, it is equally tempting to begin with his account of the nature of reality, in particular his notion of substance as monads. Less common, but perhaps equally likely, starting points might reside in Leibniz the mathematician, the theologian, or the physicist. These controversies, however, already contain a lesson: to an important degree it doesn’t matter. So integrated were his various philosophical interests—so tightly laced together into a system—that one ought to be able to begin anywhere and reconstruct the whole. Or at least Leibniz evidently thought so, since often he uses an idea from one part of his philosophy to concisely prove something in an apparently quite distant philosophical region. However, due to this systematic nature of his philosophy, in which every idea seems to rely upon others, engaging Leibniz’s ideas often proves to be challenging.

2. The Idea of Truth

According to Leibniz, a conception of truth has important consequences for a conception of reality and how it is to be understood at its most profound level. Intuitively, a proposition is true when its content is adequate to the situation in the world to which it refers. For example, “the sky is gray” is true if and only if the thing out there in the world called “the sky” is actually the color called “gray” at the time the proposition is stated. This, however, raises issues about the relationship of language to the world and what “adequacy” consists in.

Leibniz claims that one can bypass problems with the intuitive notion of truth, at least for the moment. Truth, according to Leibniz, is simply a proposition in which the predicate is contained in the subject. The predicate is what is asserted; the subject is what the assertion is about. All true propositions, then, can be expressed by the following general form: “subject is predicate.” This is not, by any means, an idea unique to Leibniz. What is unique, however, is the single-mindedness with which he pursues the consequences of such an idea of truth. (See, for example, “Correspondence with Arnauld,” 14 July 1686.)

This notion of truth seems straight-forward enough for what are commonly called analytic propositions, such as “Blue is a color,” which has more to do with the definition of blue than it does with the world. The notion of color is part of the notion of blue. Similarly, in the basic logical truth “A is A,” the predicate is not just contained in the subject, it is the subject. But, Leibniz states that this “being contained” is implicitly or virtually the case with other truths (see “Primary Truths” and “The Nature of Truth”). Take, for example, the statement “Peter is ill.” Intuitively, this proposition is true only if it refers to a real world in which Peter is, in fact, ill. Leibniz, however, analyzes this as follows: if one knew everything there is to know about Peter, that is, if one had a complete concept of Peter, one would also know (among many other things) that he is ill at the moment. Therefore, the statement “Peter is ill” is true not primarilybecause of some reference to the world, but in the first instance because someone has the concept of Peter, which is the subject of the proposition, and that concept contains (as a predicate) his being ill. Of course, it may be the case that one happens to know that Peter was ill because one refers to the world (perhaps sees him cough repeatedly). But the fact that one finds out about Peter in this way does not make the statement that “Peter is ill” true and thus a piece of knowledge because of that reference. One must distinguish the concept of truth from pragmatic or methodological issues of how one happens to find out about that truth, or what one can do with the truth. The latter, according to Leibniz, are completely irrelevant to the question “What is truth?” in itself.

Leibniz also claims that a statement is true for all time—that is, whenever the statement is made. So, for example, the statement “Peter is ill (on January 1st, 1999)” was true in the year 1998 (even though no one knew it yet) as well as in the year 2000 (even though everyone may have forgotten about the illness by then). It was also true a million years ago, and will be true a million years from now, although it is very unlikely that anyone will actually know this truth at those times.

Leibniz’s own example is of Julius Caesar. He writes:

For if some person were capable of completing the whole demonstration by means of which he could prove this connection of the subject (which is Caesar) with the predicate (which is his successful enterprise [winning the battle of Pharsalus, etc.]), he would then show that the future dictatorship of Caesar had its foundation in his notion or nature, that a reason can be found there why he resolved to cross the Rubicon rather than stop, and why he won rather than lost the day at Pharsalus… (Discourse on Metaphysics, §13).

However, there are several ideas Leibniz introduces in this passage that require further investigation. What is meant by “completing the whole demonstration,” by something having a “foundation,” or by “a reason can be found?”

3. Sufficient Reason

As previously stated, for any proposition, truth is defined by Leibniz in the same way: the predicate is contained in the subject. It only takes a little thought to realize that for any one subject (like Peter or Caesar), the number of predicates which are true of it will be infinite (or at least very large), for they must include every last thing Peter or Caesar did or will do, as well as everything that did or will ever happen to them. But now it is natural to ask: Why do all these predicates come together in the one subject? It could be that the predicates are a quite arbitrary or random collection—although Leibniz does not believe this, and it is certainly not intuitive. Rather, one predicate or set of predicates explains another. For example, Peter’s coming into contact with a virus explains his illness. Or, Caesar’s ambition and boldness explains why he decided to cross the Rubicon. So, many (at least) of the predicates that are true of a subject “hang together” as a network of explanations.

Leibniz goes further still by claiming that for every predicate that is true of a subject, there must be a set of other true predicates which constitute a sufficient reason for its being true. This he calls the principle of sufficient reason—that there must be a sufficient reason for why things are as they are and not otherwise. This is why he uses words like “foundation” and “reason” in the quotation above. Unless this were true, Leibniz argues, the universe would not make any sense, and science and philosophy both would be impossible (see, for example, New Essays on Human Understanding, preface, p. 66). Moreover, it would be impossible to account for a basic notion like identity unless there was a sufficient reason why Caesar, for example, with his particular properties at a given time, is identical with the Caesar who existed a week prior with such different properties (see “Remarks on Arnauld’s Letter,” May 1686).

The principle of sufficient reason also accounts for why Leibniz uses the phrase “completing the whole demonstration” in the above quote. If the complete concept of the subject (that is, all of its true predicates) together constitutes a complete network of explanation, then these explanations can be followed forward and backward, so to speak, at least in principle. That is, working forward, one coulddeduce that Caesar will cross the Rubicon from a all the predicates that have been true of him; or, working backward, one can deduce from all those predicates true of Caesar at his death the reasons why he won the battle of Pharsalus. The “whole demonstration,” then, is the revelation of the logical structure of the network of explanations that make Caesar who he is.

However, this is clearly not something the average person can do. Human minds are not subtle and capacious enough for a task which may be infinite. Still, in a more limited way, one can certainly talk about personalities, characters, and causes or reasons for things. The quotation from Leibniz given above continues:

… [he who completed the whole demonstration would then show] that it was rational and therefore definite that this would happen, but not that it is necessary in itself, or that the contrary implies a contradiction (Discourse on Metaphysics, §13).

These qualifications are quite important for Leibniz. It was often suggested by Leibniz’s contemporaries (and is still being suggested) that his idea of the sufficient reason of all the predicates of a subject meant that everything true of a subject is necessarily true. This might entail that Caesar did not choose to cross the Rubicon, but that he was acting in a determined manner, like a machine. In other words, Leibniz seems to be denying any sort of free will. The free will problem will be discussed in more detail below, but for the moment, a few observations can be made.

First, Leibniz claims that Caesar’s crossing of the Rubicon is not necessary in the sense that “A is A” is necessary. Because while “A is not A” is a contradiction, Caesar’s deciding not to cross the Rubicon does not imply a contradiction. To be sure, history would have been different—even Caesar would have been different—but there is no contradiction in that strong sense. Caesar’s properties are not logically necessary.

Second, any truth about Caesar–indeed, the whole complete concept of Caesar–is not “necessary in itself.” Caesar is Caesar, but nothing about Caesar in himself proves that Caesar has to be. By contrast, “A is A” doesn’t need any other explanation for its truth. So, while every property of

Caesar is explained by some other property of Caesar, no property explains why it is true that Caesar existed. Caesar is not anecessary being.

What the precise details are of Leibniz’s account of free will remain a strenuously debated issue in Leibniz scholarship (especially what the exact nature is of these distinctions, whether he is justified in making them, and even if justified whether they yield the results he claims in the area of free will). More detail will be added to this account below, but the existence of this debate should be kept in mind throughout.

4. Substance, Briefly

At this point, it is useful to turn from a conception of truth to a conception of substance. Leibniz’s philosophy of substance will be explicated in more detail in section 8 (Substance as Monad). For the moment, simply observe that for humans (though not for God), complete concepts are always concepts of existing substances–that is, of really existing things. Leibniz writes:

Now it is obvious that all true predication has some foundation in the nature of things, and when a proposition is not identical, that is to say when the predicate is not expressly included in the subject, it must be virtually included in it.[...] This being so, we can say that the nature of an individual substance or of a complete being is to have a notion so complete that it is sufficient to include, and to allow the deduction of, all the predicates of the subject to which that notion is attributed (Discourse on Metaphysics, §8, emphasis added).

To be the individual substance, Caesar, then, is to be such as to have a notion which includes everything that can truthfully be predicated of the subject Caesar. Thus, one might say that, for Leibniz, a substanceis a complete concept made real, and a complete concept is a real substance expressed or “perceived” in thought. Moreover, just as for any one predicate, the complete concept contains other predicates which explain that predicate, for any given property of a substance, the complete individual substance will itself be the explanation for that property. Caesar chose to cross the Rubicon for many complex reasons, but they all boil down to this: that was the kind of individual Caesar was.

Leibniz has much more to say about substance, but he claims that it all follows from this insight. However, the exact relationship Leibniz intended between the logical idea of a complete concept and the metaphysical idea of a substance is still debated in Leibniz scholarship.

5. Necessary Being

The complete concept of Caesar, according to Leibniz, cannot explain itself in its entirety. Expressed ontologically, this means that Caesar himself provides no explanation of why Caesar should have existed at all–Caesar is a contingent being. “Contingent” here simply means something that could have been otherwise; in the case of Caesar as a being, then, it means something that could have not existed at all. The principle of sufficient reason must not only apply to each predicate in the complete concept of a subject, but also it must apply to the concept itself in its entirety as the concept of an existing thing. Thus, there must be a sufficient reason for why this particular substance, Caesar, exists, rather than some other substance, or nothing at all.

What, then, sufficiently explains a contingent being such as Caesar? Possibly other substances, such as his parents, and they in turn are explained by still others? But the entire course of the universe, the total aggregate of substances across space and time, are one and all contingent. There are other possible things, to be sure; but there are also other possible universes that could have existed but did not. The totality of contingent things themselves do not sufficiently explain themselves. Here again, the principle of sufficient reason applies. There must be, Leibniz insists, something beyond the totality of contingent things which explains them, something which is itself necessary and

therefore requires no explanation other than itself. (Note, however, that this does not assume an origin or beginning in any sense. Even if time stretched infinitely into the past, there would still be no explanation for the total course of things.)

God, according to Leibniz, is the necessary being which constitutes the sufficient explanation of the totality of contingent things–why the universe is this way rather than any other. Thus far, God’s necessity is the only thing mentioned about such a being (there is not much religious or theological about this initially bare metaphysical concept). God as a being may be necessary, but if the contingent universe were simply a random or arbitrary act of God, then God would not constitute the required explanation of all things. In other words, God must not only be necessary, but also the source of the intelligibility of all things. It must be possible, therefore, to inquire into the reasons God had for authorizing or allowing this, rather than any other, universe to be the one that actually exists. And if God is to be the explanation of the intelligibility of the universe, then God must have access to that intelligibility, such that God could be said to know what it is that is being allowed to exist–that is, God must have the ability to grasp complete concepts, and to see at once the “whole demonstration” discussed above. God so far is therefore (i) a necessary being, (ii) the explanation of the universe, and (iii) the infinite intelligence.

Here Leibniz famously brings in the notion of perfection (see, for example, “A Specimen of Discoveries”). One has to try to imagine God, outside of time, contemplating the infinite universe that “he” is going to, not create, but allow to be actual and sustain in existence. In the mind of God are an infinite number of infinitely complex and complete concepts, all considered as possibly existent substances, none having any particular “right” to exist. There is just one constraint on this decision: it must not violate the other basic principle of Leibniz’s, the law of non-contradiction (also known as “the law of contradiction”). In other words, each substance may individually be possible, but they must all be possible together–the universe forming a vast, consistent, non-contradictory system. For example, God could not create a universe in which there are both more sheep than cows and more cows than sheep. God could choose a universe in which there is the greatest possible quantity of pizza, or in which everything is purple, and so on. However, according to Leibniz, God chooses the universe that is the most perfect. This principle of perfection is not surprising since it is most consummate with the idea of God as an infinite being; to choose any other less perfect universe would be to choose a lesser universe. Thus, according to Leibniz, the actual world is the best of all possible worlds. (This claim, and its apparent implications, were very effectively and famously satirized by Voltaire in his Candide. Note also that Leibniz is often taken as an ancestor of modern possible worlds semantics; however, it is undeniable that at least the context and purpose of Leibniz’s notion of a possible universe was quite different.) Leibniz explores the theological

consequences of this at, for example, the end of Discourse on Metaphysics. (There may be a difficult theological implication here: must God be thought of as constrained, first by the concept of perfection, and then by the systemic nature of his creation? Leibniz attempts, for example, in the “Correspondence with Arnauld” to escape this conclusion.)

To try to understand further this notion of perfection, Leibniz explores several concepts in various writings: notions of the best, the beautiful, the simply compossible, greatest variety or the greatest quantity of essence. The last of these is the explanation he continually comes back to: perfection simply means the greatest quantity of essence, which is to say the greatest richness and variety in each substance, compatible with the least number of basic laws, so as to exhibit an intelligible order that is “distinctly thinkable” in the variety (see “A Resume of Metaphysics;” there is a relationship to the Medieval, and particularly Augustine, notion of plenitude). Leibniz seems to understand this principle as simply self-evident. It certainly seems to be a big jump to the aesthetic, moral, and wise God from the ontological conception of God deduced above. However, Leibniz may have a point in arguing that it would be absurd in some sense for an infinite being to choose anything other than an infinitely rich and thus perfect universe. He also finds this aesthetic observed throughout nature: natural forms tend towards a maximum of variety compatible with orderliness. Nevertheless, contemporary philosophers generally find Leibniz’s conclusion here to not strictly follow from the previous considerations.

For Leibniz, this forms a proof for the existence of God (see Monadology §§37-39 and “A Specimen of Discoveries”). In fact, it is a version of the third of the cosmological arguments given by St. Thomas Aquinas, and subject to many of the same difficulties. One might, for example, object in a Kantian vein that the concept of explanation, rightly demanded of all individual contingent beings, is applied beyond its proper sphere in demanding an explanation of the totality of contingent beings. But Leibniz might well counter that this objection assumes a whole theory of the “proper spheres” of concepts.

6. Problems of Freedom, Sin, and Evil

a. Freedom and Sin

Leibniz’s conception of God, however, may seem to cause more problems than it solves. For example, if the complete concept of any being, such as a human being, is known for all time, and was chosen by God for existence, then is such a being free? It seems that what one means by “freedom” is that the outcome is not predictable, as opposed to, for example, the way in which the operation of a washing machine or the addition of two numbers is predictable. Further, what must one make of morality and sin? Why, for example, should God punish Adam and Eve for sinning when they seemed to have no free choice, since God knew in advance (predicted and, indeed, made it the case) that they were going to sin?

While Leibniz’s philosophical system demands a certain sense of determinism about the universe, he does not want to deny the existence of free will. Leibniz thus seeks to substantiate a form or compatibilism(that is, a view which takes determinism to be compatible with free will). In order to accomplish this, Leibniz distinguishes between several ways in which things might be determined in advance. Whatever is determined is clearly true. Truth, however, comes in several varieties. (Much of the following is taken from the set of distinctions Leibniz makes in “Necessary and Contingent Truths;” Leibniz makes similar but rarely identical sets of distinctions in a variety of texts.)

1. Truths of EssenceThese come in two varieties:

a. Primary/original truth: the law of non-contradiction, for example.

b. Eternal, metaphysical, or geometrical truths: the laws of arithmetic or geometry, for example, which Leibniz claims can be reduced by a finite process of argumentation and substitution of definitions to primary truth. These are valid in all possible universes.

2. Truths of Existence, of Fact, or of HypothesisHere, arguably, Leibniz sees four varieties:

a. Absolutely universal truths: those truths definitive of this universe as being the most perfect universe. Leibniz writes: “Indeed, I think that in this series of things there are certain propositions which are true with absolute universality, and which cannot be violated even by a miracle” (“Necessary and Contingent Truths”).

b. Universal-physical truths: the laws of physics and other such efficient causes, for example; truths which hold universally of all substances in this, but not in all possible, universes, but which also could, in principle, be violated by a miracle, in accordance with overall divine providence.

c. Individual metaphysical truths: truths about the properties of individual substances, where those properties follow from the complete concept–and thus are apparent to God, but do not follow any “subordinate universal laws.” Deduction of such truths is available to no being, no matter how perfect or perceptive, other than God.

d. Hypothetical truths: only truths of essence can be necessary, absolutely and strictly speaking. All other truths, such as the actions of Caesar, are only “hypothetically” necessary–that is, only on the hypothesis that a universe exists as it is, with beings such as these in it (see Discourse on Metaphysics, §13 and “Correspondence with Arnauld,” April 12th, 1686).

A person’s actions are, therefore, not necessary by definition (regardless, at this point, of which type of “truth of existence” they fall under). Thus, the concept of an individual “inclines without necessitating” (seeDiscourse on Metaphysics, §30). Leibniz further writes:

For speaking absolutely, our will is in a state of indifference, in so far as indifference is opposed to necessity, and it has the power to do otherwise, or to suspend its action altogether, both alternatives being and remaining possible. [...] It is true, however, and indeed it is certain from all eternity, that a particular soul will not make use of this power on such and such an occasion. But whose fault is that? Does it have anyone to blame but itself? (Discourse on Metaphysics, §30, emphasis added)

By “indifference,” Leibniz means a physical indifference–that is to say, there is no universal-physical truth, as defined above, which governs human action. For Leibniz, this means that human action is further freed: the will has the power to suspend its action with respect to the physical sequence of efficient causes, but also even with respect to what would otherwise be seen as a decisive final cause. Leibniz states: “For they [free or intelligent substances] are not bound by any certain subordinate laws of the universe, but act as it were by a private miracle” (“Necessary and Contingent Truths”).

Minds, then, are different from mechanical causes. (As it will be shown below, Leibniz goes against the trend of 17th and 18th century thought by reintroducing the Aristotelian and Scholastic notion of a final cause and, indeed, substantial forms.) Although Leibniz occasionally uses the analogy of a machine to describe the soul, the kinds of forces and causes operative in the former are simply inapplicable to the latter. Thus, if by individual free choice one means an individual action that cannot be known in advance by even an infinitely subtle application of the laws of physics, chemistry, or biology, then humans have free choice in that sense as well.

Leibniz also offers the following additional arguments for his particular conception of human free will:

(i) Freedom as “unpredictability” might be taken to mean freedom as an act uncaused. But this makes no sense, for free choice is not randomness. Caesar’s free act, for example, has a cause–namely, Caesar. Why should one complain when the individual concept of Caesar intrinsically determines what Caesar does? Isn’t Caesar free if he is the source of his action, and not anyone or anything else?

(ii) A necessary ignorance of the future is practically, perhaps even logically, equivalent to freedom. Again, grasping the full explanation of any predicate that lies in the complete concept is an infinite task. To help illustrate the distinction between contingent and necessary truths, Leibniz makes a famous analogy with the incommensurability of any whole number or fraction with a “surd” (for example, the square root of two, the value of which cannot be represented numerically by any finite series of numbers.) For finite human minds, that incommensurability is a positive fact, just like contingency–no matter that for God neither calculation is impossible, or even more difficult. Thus contingent truths can in principle be known from all time, but necessarily not by a human being (see, for example, “On Freedom”). Leibniz writes: “Instead of wondering about what you cannot know and what can tell you nothing, act according to your duty, which you do know” (Discourse on Metaphysics, §30). (It should be pointed out that this is somewhat more than an analogy, since it is closely related to the kinds of problems infinitesimal calculus was designed to deal with–and Leibniz takes the possibility of a calculus as having real metaphysical implications.)

(iii) A famous scholastic debate concerned the so-called “Sloth Syllogism.” If everything is fated, the argument goes, then whatever action one “does” will or will not happen whether or not one wills it, therefore one need not will anything at all. One can just be a sloth, and let the universe happen. Leibniz thinks this is absurd–indeed, immoral. The will of an individual matters. If John Doe is the kind of person who is a sloth, then (everything else being the same) the course of his life will indeed be quite different than if he is the kind of person (like Caesar) who takes events by the scruff of the neck.

(iv) What many philosophers mean by “contingent” is that an individual predicate “could have been different,” and everything else the same. For Leibniz, this is impossible. To change one predicate means to alter the whole complete concept, the substance, and with it the whole universe. Leibniz thus claims that philosophers of a more radical sense of freedom do not take seriously the extent to which the universe is an integrated network of explanations, and that this in turn has implications for the idea of contingency (see the discussion of Adam in Leibniz’s letter to Landgraf Ernst von Hessen-Rheinfels, April 12, 1686). Thus, contingent events, even one’s free acts, must be part of the perfection of the universe. Although, that does not mean that all contingent events are so in the same way.

According to Leibniz, any remaining objections to this idea of free will only result from a metaphysically incoherent idea of what freedom means. There is no question that Leibniz introduced a spirited and powerful position into the age-old philosophical debate concerning free will. Which position is “metaphysically incoherent,” however, remains under debate. (For more on the philosophical debate of free will, see “Free Will“.)

b. Problem of Evil

Leibniz’s approach to the classic problem of evil is similar. The problem of evil, for Leibniz, can be put in the following way: If God is supremely good, and the creator (or author) of the best possible universe, then why is there so much pain and sin in the world? Leibniz claims that this apparent paradox is not a real problem. Leibniz coined the term “theodicy” to refer to an attempt to reconcile God’s supremely benevolent and all-good nature with the evil in the world. Thus, Leibniz’s Theodicy is largely a proposed solution to the problem of evil. However, his thoughts on the issue are to be found spread over many texts. (For more on the problem of evil, see the entries “The Evidential Problem of Evil” and “The Logical Problem of Evil.”)

Here, very briefly, are three of Leibniz’s main replies to the problem of evil:

(i) Human minds are only only aware of a small fraction of the universe. To judge it full of misery on this small fraction is presumptuous. Just as the true design–or, indeed, any design–of a painting is not visible from viewing a small corner of it, so the proper order of the universe exceeds one’s ability to judge it.

(ii) The best possible universe does not mean no evil, but that less overall evil is impossible.

(iii) Similarly to the previous argument, and in the best Neo-Platonist tradition, Leibniz claims that evil and sin are negations of positive reality. All created beings are limitations and imperfect; therefore evil and sin are necessary for created beings (see Discourse on Metaphysics, §30).

7. Space, Time, and Indiscernibles

a. Against the Absolute Theory

Between 1715 and 1716, at the request of Caroline, Princess of Wales, a series of long letters passed between Leibniz and the English physicist, theologian, and friend of Newton, Samuel Clarke. It is generally assumed that Newton had a hand in Clarke’s end of the correspondence. They were published in Germany and in England soon after the correspondence ceased and became one of the most widely read philosophical books of the 18th Century. Leibniz and Clarke had several topics of debate: the nature of God’s interaction with the created world, the nature of miracles, vacua, gravity, and the nature of space and time. Although Leibniz had written about space and time previously, this correspondence is unique for its sustained and detailed account of this aspect of his philosophy. It is also worth pointing out that Leibniz (and after him Kant) continues a long tradition of philosophizing about space and time from the point of view of space, as if the two were always in a strict analogy. It is only rarely that Leibniz deals in any interesting way with time on its own (we shall return to this in section 10).

Newton, and after him Clarke, argued that space and time must be absolute (that is, fixed background constants) and in some sense really existent substances in their own right (at least, this was Leibniz’s reading of Newton). The key argument is often called the “bucket argument.” When an object moves, there must be some way of deciding upon a frame of reference for that motion. With linear motion, the frame does not matter (as far as the mathematics are concerned, it does not matter if the boat is moving away from the shore, or the shore is moving away from the boat); even linear acceleration (changing velocity but not direction) can be accounted for from various frames of reference. However, acceleration in a curve (to take Newton’s example, water forced by the sides of a bucket to swirl in a circle, and thus to rise up the sides of the bucket), could only have one frame of reference. For the water rising against the sides of the bucket can be understood if the water is moving within a stationary universe, but makes no sense if the water is stationary and the universe is spinning. Such curved acceleration requires the postulation of absolute space which makes possible fixed and unique frames of reference. (Similar problems made Einstein’s General Theory of Relativity so much more mathematically complicated than the Special Theory.)

Leibniz, however, has a completely different understanding of space and time. First of all, Leibniz finds the idea that space and time might be substances or substance-like absurd (see, for example, “Correspondence with Clarke,” Leibniz’s Fourth Paper, §8ff). In short, an empty space would be a substance with no properties; it will be a substance that even God cannot modify or destroy.

But Leibniz’s most famous arguments for his theory of space and time stem from the principle of sufficient reason (the principle that everything which happens has, at least in principle, an explanation of why it happened as it did and not otherwise). From this principle, together with the law of non-contradiction, Leibniz believes that there follows a third: the principle of the identity of indiscernibles, which states that any entities which are indiscernible with respect to their properties are identical. Leibniz is fond of using leaves as an example. Two leaves often look absolutely identical. But, Leibniz argues, if “two” things are alike in every respect, then they are the same object, and not two things at all. So, it must be the case that no two leaves are ever exactly alike.

Leibniz’s support for the principles of the identity of indiscernibles primarily derives from his commitment to the principle of sufficient reason in the following way. If any objects are in every way the same, but actually distinct, then there would be no sufficient reason (that is, no possible

explanation) for why the first is where (and when) it is, and the second is where (and when) it is, and not the other way around. If, then, one posits the possible existence of two identical things (things that differ in number only–that is, one can count them, but that is all), then one also posits the existence of an absurd universe, one in which the principle of sufficient reason is not universally true. Leibniz often expresses this in terms of God: if two things were identical, there would be no sufficient reason for God to choose to put one in the first place and the other in the second place. (Note that Leibniz’s argument relates to a scholastic debate centered on the notion of “Buridan’s Ass.”)

Similar considerations apply to Newtonian absolute space. Leibniz’s argument against the Newton-Clarke position can be understood here as two related reductio ad absurdum arguments. The first concerns the violation of the principle of the identity of indiscernibles. Suppose that space is absolute. Since every region of space would be indiscernible from any other and spatial relations would be construed as extrinsic, it would be possible for two substances to be indiscernible yet distinct in virtue of being in different locations. But this is absurd, Leibniz argues, because it violates the principle of the identity of indiscernibles. Therefore, space must not be absolute (see “Correspondence with Clarke,” Leibniz’s Third Paper). The second reductio concerns the violation of the principle of sufficient reason. Suppose that space is absolute. Leibniz argues that there would then be no sufficient reason for why the whole universe was created here instead of two meters to the left (because no region of space is discernible from any other). Thus, absolute space is absurd, because it violates the principle of sufficient reason (see “Correspondence with Clarke,” Leibniz’s Fourth Paper). (Analogous problems are thought to result from a conception of absolute time.)

b. The Relational Theory

That is the negative portion of Leibniz’s argument. But what does all this say about space? For Leibniz, the location of an object is not a property of an independent space, but a property of the located object itself (and also of every other object relative to it). This means that an object here can indeed be different from an object located elsewhere simply by virtue of its different location, because that location is a real property of it. That is, space and time are internal or intrinsic features of the complete concepts of things, not extrinsic. Let us return to the two identical leaves. All of their properties are the same, except that they are in different locations. But that fact alone makes them completely different substances. To swap them would not just involve moving things in an indifferent space, but would involve changing the things themselves. That is, if the leaf were located

elsewhere, it would be a different leaf. A change of location is a change in the object itself, since spatial properties are intrinsic (similarly with location in time).

Leibniz’s view has two major implications. First, there is no absolute location in either space or time; location is always the situation of an object or event relative to other objects and events. Second, space and time are not in themselves real (that is, not substances). Space and time are, rather, ideal. Space and time are just metaphysically illegitimate ways of perceiving certain virtual relations between substances. They are phenomena or, strictly speaking, illusions (although they are illusions that are well-founded upon the internal properties of substances). Thus, illusion and science are fully compatible. For God, who can grasp all at once complete concepts, there is not only no space but also no temptation of an illusion of space. Leibniz uses the analogy of the experience of a building as opposed to its blueprint, its overall design (see, for example, “Correspondence with Arnauld” 12 April 1686 and Monadology §57). It is sometimes convenient to think of space and time as something “out there,” over and above the entities and their relations to each other, but this convenience must not be confused with reality. Space is nothing but the order of co-existent objects; time nothing but the order of successive events. This is usually called a relational theory of space and time. (For more information, see §6 on relative vs. absolute theories of time).

Space and time, according to Leibniz, are thus the hypostatizations of ideal relations, which are real insofar as they symbolize real differences in substances, but illusions to the extent that (i) space or time are taken as a thing in itself, or (ii) spatial/temporal relations are taken to be irreducibly exterior to substances, or (iii) extension or duration are taken to be a real or even fundamental property of substances. Take the analogy of a virtual reality computer program. What one sees on the screen (or in a specially designed virtual reality headset) is the illusion of space and time. Within the computer’s memory are just numbers (and ultimately mere binary information) linked together. These numbers describe in an essentially non-spatial and temporal way a virtual space and time, within which things can “exist,” “move” and “do things.” For example, in the computer’s memory might be stored the number seven, corresponding to a bird. This, in turn, is linked to four further numbers representing three dimensions of space and one of time–that is, the bird’s position. Suppose further the computer contains also the number one, corresponding to the viewer and again linked to four further numbers for the viewer’s position, plus another three giving the direction in which the viewer’s virtual eyes are looking. The bird appears in the viewer’s headset, then, when the fourth number associated with the bird is the same as the viewer’s fourth number (they are together in time), and when the first three numbers of the bird (its position in virtual space) are in a certain algebraic relation to the number representing the viewer’s position and point of view. Space and time are reduced to non-spatial and non-temporal numbers. For Leibniz, God in this analogy apprehends these numbers as numbers, rather than through their translation into space and time.

c. Objections and Replies

This, however, raises a serious logical problem for Leibniz. Recall Leibniz’s theory of truth as the containedness of a predicate in a subject. This seemed acceptable, perhaps, for propositions such as “Caesar crossed the Rubicon” or “Peter is ill.” But what about “This leaf is to the left of that leaf?” The latter proposition involves not one subject, but three (the two leaves, and whatever is occupying the point-of-view from which the one is “to the left”). Leibniz has to argue that all relational predicates are in fact reducible to internal properties of each of the three substances. This includes time, as well as relations such as “the sister of” or “is angry at.” But can all relations be so reduced, at least without radically deforming their sense? Modern logicians often see this as the major flaw in Leibniz’s logic and, by extension, in his metaphysics.

Furthermore, Leibniz must provide a response to the Newtonian bucket argument. Indeed, Leibniz thinks that one simply needs to provide a rule for the reduction of relations. For linear motion the virtual relation is reducible to either or both the object and the universe around it. For non-linear motion, one must posit a rule such that the relation is not symmetrically reducible to either of the subjects (bucket, or universe around it). Rather, non-linear motion is assigned only when, and precisely to the extent that, the one subject shows the effects of the motion. That is, the motion is a

property of the water, if the water shows the effects (see “Correspondence with Clarke,” Leibniz’s Fifth Paper, §53). Perhaps it seems strange that the laws of nature should be different for linear as opposed to non-linear motion. It sounds like anarbitrary new law of nature, but Leibniz might respond that it is no more arbitrary that any other law of nature; people have just become used to the illusion of space and time as extrinsic relations of entities that they are not used to thinking in these terms.

8. Substance as Monad

We are now, finally, ready to get a picture of what Leibniz thinks the universe is really like. It is a strange, and strangely compelling, place. Around the end of the Seventeenth Century, Leibniz famously began to use the word “monad” as his name for substance. “Monad” means that which is one, has no parts and is therefore indivisible. These are the fundamental existing things, according to Leibniz. His theory of monads is meant to be a superior alternative to the theory of atoms that was becoming popular in natural philosophy at the time. Leibniz has many reasons for distinguishing monads from atoms. The easiest to understand is perhaps that while atoms are meant to be the smallest unit of extension out of which all larger extended things are built, monads are non-extended (recall that space is an illusion on Leibniz’s view).

a. Monads and Complete Concepts

We must begin to understand what a monad is by beginning from the idea of a complete concept. As previously stated, a substance (that is, monad) is that reality which the complete concept represents. Acomplete concept contains within itself all the predicates of the subject of which it is the concept, and these predicates are related by sufficient reasons into a vast single network of explanation. So, relatedly, the monad must not only exhibit properties, but contain within itself “virtually” or “potentially” all the properties it will exhibit in the future, as well as contain the “trace” of all the properties it did exhibit in the past. In Leibniz’s extraordinary phrase, found frequently in his later work, the monad is “pregnant” with the future and “laden” with the past (see, for example, Monadology §22). All these properties are “folded up” within the monad; they unfold when they have sufficient reason to do so (see, for example,Monadology §61). Furthermore, the network of explanation is indivisible; to divide it would either leave some predicates without a sufficient reason or merely separate two substances that never belonged together in the first place. Correspondingly, the monad is one, simple and indivisible.

Just as in the analysis of space and time Leibniz argues that all relational predicates are actually interior predicates of some complete concept, so the monad’s properties include all of its relations to every other monad in the universe. A monad, then, is self-sufficient. Having all these properties within itself, it doesn’t need to be actually related to or influenced by another other monad. Leibniz writes:

So if I were capable of considering distinctly everything which is happening or appearing to me now, I would be able to see in it everything which will ever happen or appear to me for all time. And it would not be prevented, and would still happen to me, even if everything outside me were destroyed, so long as there remained only God and me (Discourse on Metaphysics, §14).

Thus, just like space and time, cause and effect is a “well-founded” illusion. According to Leibniz, causation is to be account for by saying that one thing, A, causes another, B, when the virtual relation between them is more clearly and simply expressed in A than in B. But metaphysically, Leibniz argues, it makes no difference which way around the relation is understood, because the relation itself is not real. Leibniz writes:

Thus, in strict metaphysical precision, we have no more reason to say that the ship pushes the water to produce this large number of circles…than to say that the water is caused to produce all these circles and that it causes the ship to move accordingly (“Draft letter to Arnauld,” 8 December 1686).

Leibniz goes on to insist that the first direction of explanation is much simpler, since the second would involve leaping directly to the action of God to explain the extraordinary action of so many individual bits of water. But that simplicity is hardly the same as truth.

b. Pre-established Harmony, Windowlessness, and Mirroring

So, instead of cause and effect being the basic agency of change, Leibniz is offering a theory of pre-established harmony (sometimes referred to as the hypothesis of concomitance) to understand the apparently inter-related behavior of things. Consider the common analogy of two clocks. The two clocks are on different sides of a room and both keep good time (that is, they tell the same time). Now, someone who didn’t know how clocks work might suspect that one was the master clock and it caused the other clock to always follow it. When two things behave in corresponding ways, then it is often assumed (without any real evidence) that there is causation occurring. But another person who knew about clocks would explain that the two clocks have no influence one on the other, but rather they have a common cause (for example, in the last person to set and wind them). Since then, they have been independently running in sync with one another, not causing each other. On Leibniz’s view, every monad is like a clock, behaving independently of other monads. Nevertheless, every monad is synchronized with one another by God, according to his vast conception of the perfect universe. (We must be careful, however, not to take this mechanical image of a clock too literally. Not all monads are explicable in terms of physical, efficient causes.)

In accordance with his theory of pre-established harmony, Leibniz argues that monads do not affect one another and that each monad expresses the entire universe. He has rather unique and extraordinary set of phrases for this; Leibniz states that every monad mirrors the whole of the universe in that it expresses every other monad, but no monad has a window through which it could actually receive or supply causal influences (see Monadology, §7 & §56). Furthermore, since a monad cannot be influenced, there is no way for a monad to be born or destroyed (except by God through a miracle–defined as something outside the natural course of events). All monads are thus eternal. (It is fair to say that Leibniz’s attempt to account for what happens to “souls” before the birth of body, and after its death, lead him to some colorful, but rather strained, speculations.)

9. Implications of Conceiving Substances as Monads

We will examine briefly four important implications of Leibniz’s account of substance: first, the distinction between metaphysical truth and phenomenal description; second, the idea of little perceptions; third, the infinitely composite nature of all body; and fourth, innate ideas.

a. Levels of Reality

Leibniz posits a distinction between levels or “spheres” in his account of reality (“Discourse on Metaphysics,” §10). The primary, most fundamental level of reality is the metaphysical level, which includes only monads, their perceptions, and their appetitions (no causality, no space, no time–at least as ordinarily understood–each monad spontaneously unfolding according to the kind of thing that it is). Thephenomenal or descriptive level involves what appears to be happening from the finite, imperfect perspective of human minds (things cause one another in space and time). Science’s object is the latter, which is an illusion, but in which nothing happens that is not based upon what really happens in the metaphysical level (that is, the illusion is “well-founded”). Therefore, the laws of physics are perfectly correct, as a description. (Berkeley borrows this idea,

see especially his “De Motu,” and Kant produces a highly original version of it.) Indeed, Leibniz believes, following Descartes and many other materialists, that all such laws are mechanical in nature, exclusively involving the interaction of momenta and masses–hence his accusation that Newton’s idea of gravity is merely “occult.” However, at the metaphysical level, no account of reality could be less mechanical. Not surprisingly, then, Leibniz’s own contributions to physical science were in the fields of the theory of momentum and engineering.

A serious error would arise only if one took the “objects” of science (matter, motion, space, time, etc.) as if they were real in themselves. Consider the following analogy: in monitoring a nation’s economy, it is sometimes convenient to speak of a retail price index, which is a way of keeping track of the average change in the prices of millions of items. But there is nothing for sale anywhere which costs just that amount. As a measure it works well, provided one does not take it literally. Science, in order to be possible for finite minds, involves that kind of simplification or “abbreviation” (see, for example, “Letter to Arnauld,” 30 April 1687).

b. Little Perceptions

Leibniz is one of the first philosophers to have analyzed the importance of that which is “unconscious” in one’s mental life. That a monad is a “mirror” of the whole universe entails that one’s soul will actually have an infinite number and complexity of perceptions. Obviously, however, one does not apperceive (that is, one is not conscious of) all these little perceptions, as Leibniz calls them. Thus, perception for Leibniz does not mean apperception. (Leibniz argues that this is a major error on Descartes’ part.) Further, where one is conscious of some perception, it will be of a blurred composite perception. Leibniz’s analogy is of the roar of the waves of the beach: the seemingly singular sound of which one is conscious is in fact made up of a vast number of individual sounds of which one is not conscious–droplets of water smacking into one another.

For Leibniz, little perceptions are an important philosophical insight. First and foremost, this relates to one of Leibniz’s main general principles, the principle of continuity. Nature, Leibniz claims, “never makes leaps” (New Essays on Human Understanding, 56). This follows, Leibniz believes, from the principle of sufficient reason together with the idea of the perfection of the universe (consisting of something like plenitude). But the idea of little perceptions allows Leibniz to account for how such continuity actually happens even in everyday circumstances. The principle of continuity is very important for Leibniz’s physics (see “Specimen Dynamicum”) and turns up in Leibniz’s account of change in the monad (see below).

Second, little perceptions explain the acquisition of innumerable minor habits and customs, which make up a huge part of one’s distinctiveness as an individual personality. Such habits accumulate continuously and gradually, rather than all at once like decisions, and thus completely bypass the conscious will. Further, these little perceptions account for one’s pre-conscious connection with the world. For Leibniz, one’s relation with the world is not one just of knowledge, or of apperceived sensation. An individual’s relation with the world is richer than either of these, a kind of background feeling of being-a-part-of. (Thus, a thorough-going skepticism, however plausible at a logical level, is ultimately absurd.)

Finally, Leibniz’s idea of little perceptions gives a phenomenal (rather than metaphysical) account for the impossibility of real indiscernibles: there will always be differences in the petite perceptions of otherwise very similar monads. The differences may not be observable at the moment, but will “unfold in the fullness of time” into a discernible difference (New Essays on Human Understanding, 245-6).

c. Composites and Substantial Forms

According to Leibniz, everything one perceives which is a unified being must be a single monad. Everything else is a composite of many monads. A coffee cup, for example, is made of many monads

(an infinite number, actually). In everyday life, one tends to call it a single thing only because the monads all act together. One’s soul, however, and the soul of every other living thing, is a single monad which “controls” a composite body. Leibniz thus says that, at least for living things, one must posit substantial forms, as the principle of the unity of certain living composites. (See, for example, “A New System of Nature.” The term is derived from Aristotle: that which structures and governs the changes of mere matter in order to make a thing what it is.) One’s soul, a monad otherwise like any other monad, thus becomes the substantial form of one’s otherwise merely aggregate body.

Furthermore, according to Leibniz, such composite bodies must be made of an infinite number of other inanimate as well as animated monads. This follows from the universe being the most perfect possible, which, again, seems to mean the richest in controlled complexity, in “plenitude.” Leibniz argues that it would be a great waste of possible perfection to only allow living beings to have bodies at that particular level of aggregation with which one is phenomenally familiar. (Perhaps Leibniz was understandably impressed by the different levels of magnitude being revealed by relatively recently invented instruments like the microscope and telescope.) Leibniz writes:

Every portion of matter can be thought of as a garden full of plants, or as a pond full of fish. But every branch of the plant, every part of the animal, and every drop of its vital fluids, is another such garden, or another such pool. [...] Thus there is no uncultivated ground in the universe; nothing barren, nothing dead. (Monadology, §§67 & 69)

(Note: Although there is an extraordinary sublimity of such an image, Leibniz is often accused of making rather too much of an inadequate conception of the infinite.)

Further, the particular monads making up one’s body are constantly changing as one breaths in and out, sheds skin, etc., although not all at once. The substantial form is thus a unified explanation of bodily form and function. A mere chunk of stuff has, of course, an explanation, but not a unified one–not in one monad, the soul. Leibniz thus distinguishes four types of monads: humans, animals, plants, and matter. All have perceptions, in the sense that they have internal properties that “express” external relations; the first three have substantial forms, and thus appetition; the first two have memory; but only the first has reason (see Monadology §§18-19 & 29).

d. Innate Ideas

An innate idea is any idea which is intrinsic to the mind rather than arriving in some way from outside it. During this period in philosophy, innate ideas tended to be opposed to the thorough-going empiricism of Locke. Like Descartes before him–and for many of the same reasons–Leibniz found it necessary to posit the existence of innate ideas. At the metaphysical level, since monads have no “windows,” it must be the case that all ideas are innate. That is to say, an idea in one’s monad/soul is just another property of that monad, which happens according to an entirely internal explanation represented by the complete concept. But at the phenomenal level, it is certainly the case that many ideas are represented as arriving through one’s senses. In general, at least any relation in space or time will appear in this way.

Thus, one could imagine Leibniz being a thorough-going empiricist at the phenomenal level of description. This would amount to the claim that the metaphysically true innateness of all ideas is epistemologically useless information. Leibniz finds it necessary, therefore, to advance the following arguments in favor of phenomenally innate ideas:

(i) Some ideas are characterized by universal necessity, such as ideas in geometry, logic, metaphysics, morality, and theology. But it is impossible to derive universal necessity from experience. (Note that this argument is hardly new to Leibniz.)

(ii) An innate idea need not be an idea consciously possessed (because of “little perceptions,” for example). An innate idea can be potential, as an inclination of reason, as a rigid distortion in Locke’stabula rasa. (Here, Leibniz provides the famous analogy of the veins in the marble prior to

the sculptor’s work.) It requires “attention” (especially in the form of philosophical thinking) to bring to explicit consciousness the operation, and to clarify the content, of these innate ideas.

(iii) Consider the possibility of foreseeing an event that is not similar to (and thus merely an associated repetition of) a past event. By using rational principles of physics, for example, one can analyze a situation and predict the outcome of all the masses and forces, even without ever having experienced a similar situation or outcome. This, Leibniz says, is the privilege of humans over animals (“brutes”), who only have the “shadow” of reason, because they can only move from one idea to another by association of similars (see Leibniz’s joke about empiricists in Monadology, §28).

Thus, at the phenomenal level, Leibniz can distinguish between innate and empirical ideas. An empirical idea is a property of a monad which itself expresses a relation to some other substance or which arises from another internal property that is the expression of an external substance. Although the difference between empirical and innate is in fact an illusion, it does make a difference, for example, to the methodology of the sciences. This is similar to the distinction made above between the idea of truth (as the containedness of the predicate in the subject), and the pragmatic/methodological issue of how one comes to know that truth. The latter is not irrelevant, except to the foundation and definition of truth. (Leibniz’s most extensive discussion of innate ideas, not surprisingly, is in the New Essays on Human Understanding.)

10. Monadic Activity and Time

Correlate to the inter-connectedness of predicates in the complete concept is an active power in the monad, which thus always acts out its predicates spontaneously. Predicates are, to use a fascinating metaphor of Leibniz’s, “folded up” within the monad. In later writings such as the Monadology, Leibniz describes this using the Aristotelian/Medieval idea of entelechy: the becoming actual or achievement of a potential. This word is derived from the idea of perfections. What becomes actual strives to finish or perfect the potential, to realize the complete concept, to unfold itself perfectly as what it is in its entirety. This active power is the essence of the monad. Leibniz has several different names for this property (or closely related properties) of monads: entelechy, active power, conatus or nisus (effort/striving, or urge/desire), primary force, internal principle of change, and even light (in “On the Principle of Indiscernibles”).

This activity is not just a property of human souls, but of all types of monads. This inner activity must mean not only being the source of action, but also being affected (passivity), and of resisting (inertia). Again, what one calls “passivity” is just a more complex and subtle form of activity. Both a monad’s activity and resistance, of course, follow from its complete concept, and are expressed in phenomena as causes and as effects. Change in a monad is the intelligible, constantly, and

continuously (recalling here the principle of continuity discussed above) unfolding being of a thing, from itself, to itself. “Intelligible” here means: (i) according to sufficient reason, not random or chaotic; and (ii) acting as if designed or purposed, as if alive–hence Leibniz’s contribution to the philosophical tradition of “vitalism.”

It is important to understand that this is not just a power to act, conceived as separable from the action and its result. Rather, Leibniz insists that one must understand that power together with (i) the sufficient reason of that power; (ii) the determination of the action at a certain time and in a certain way; (iii) together with all the results of the action, first as the merely potential and then as the actual. (See “On the Principle of Indiscernibles,” and Monadology §§11-15.) One is not, therefore, to understand it as a sequence of states, the individual bits of which are even ideally separable (except as an object of mere description for science), nor a sequence of causes and effects, again understood to be ideally separable (as if there could have been the cause without the effect). All this follows from the complete concept, the predicates of which are connected in one concept. Each state therefore contains the definite trace of all the past, and is (in Leibniz’s famous phrase) “pregnant” with the future.

But time, like space, is an illusion. How then is one to understand change without time? The important question is: what conception of time is being discussed? Just like space, Leibniz is objecting to any conception of time which is exterior to the objects that are normally said to be “in” time (time as an exterior framework, a dimension). Also, he objects to time as mere chronology, a conception of time as a sequence of “now points” that are ideally separable from one another (that is, not essentially continuous) and are countable and orderable separately from any thing being “in” them (that is, abstract).

However, in discussing relational properties above (and, in particular, Leibniz’s response to the Newton-Clarke argument about non-linear motion), “space” was in a sense preserved as a set of rules about the representative properties of monads. Here, too, but in a more profound way, “time” is preserved immanently to the monad. The active principle of change discussed above is immanent to monads, and no one state can be separated from all the others, without completely altering the thing in question into a thing that never changes (that has only the one state for all eternity). For Leibniz, the past and future are no more disconnected, in fact less, from the present than “here” is from “there.” Both distinctions are illusions, but temporal relations in a substance form an explanatory, intelligible sequence of a self-same thing. The principle of change becomes an original, internal and active power of the thing constantly becoming the thing that it is, as the spontaneous happening and internal principle of the particular order of things which make up that substance. In other words, substances unfold, become the things God always knew them to be, in a time that is nothing other than precisely that becoming.

Time, then, has three levels, according to Leibniz

i. the atemporality or eternality of God;ii. the continuous immanent becoming-itself of the monad as entelechy;

iii. time as the external framework of a chronology of “nows.”

The difference between (ii) and (iii) is made clear by the account of the internal principle of change. The real difference between the necessary being of God and the contingent, created finitude of a human being is the difference between (i) and (ii).

11. Influence

Leibniz’s mathematics, in parallel to Newton’s, made a significant difference in European science of the 18th century. Other than that, however, his contributions as engineer or logician were relatively quickly forgotten and had to later be re-invented elsewhere.

However, Leibniz’s metaphysics was highly influential, renewing the Cartesian project of rational metaphysics, and bequeathing a set of problems and approaches that had a huge impact on much of 18th century philosophy. Kant above all would have been unthinkable without Leibniz’s philosophy, especially the accounts of space and time, of sufficient reason, of the distinction between phenomenal and metaphysical reality, and his approach to the problem of freedom. Rarely did Kant agree with his great predecessor–indeed, rendering the whole Cartesian/Leibnizian approach conceptually impossible–but the influence was nevertheless necessary. After Kant, Leibniz was more often than not a mine of individual fascinating ideas, rather than a systematic philosopher, ideas appearing (in greatly modified forms) in for example Hegelian idealism, romanticism, and Bergson.

In the 20th century, Leibniz has been widely studied by Anglo-American “analytic” philosophy as a great logician who made significant contributions to, for example, the theory of identity and modal logic. In Continental European philosophy, Leibniz has perhaps been less commonly treated as a great predecessor, although fascinating texts by Heidegger and, much later, by Deleuze, show the continuing fertility of his philosophical ideas.

David Hume (1711-1776) “Hume is our Politics, Hume is our Trade, Hume is our Philosophy, Hume is our Religion.” This statement by nineteenth century philosopher James Hutchison Stirlingreflects the unique position in intellectual thought held by Scottish philosopher David Hume. Part of Hume’s fame and importance owes to his boldly skeptical approach to a range of philosophical subjects. In epistemology, he questioned common notions of personal identity, and argued that there is no permanent “self” that continues over time. He dismissed standard accounts of causality and argued that our conceptions of cause-effect relations are grounded in habits of thinking, rather than in the perception of causal forces in the external world itself. He defended the skeptical position that human reason is inherently contradictory, and it is only through naturally-instilled beliefs that we can navigate our way through common life. In the philosophy of religion, he argued that it is unreasonable to believe testimonies of alleged miraculous events, and he hints, accordingly, that we should reject religions that are founded on miracle testimonies. Against the common belief of the time that God’s existence could be proven through a design or causal argument, Hume offered compelling criticisms of standard theistic proofs. He also advanced theories on the origin of popular religious beliefs, grounding such notions in human psychology rather than in rational argument or divine revelation. The larger aim of his critique was to disentangle philosophy from religion and thus allow philosophy to pursue its own ends without rational over-extension or psychological corruption.  In moral theory, against the common view that God plays an important role in the creation and reinforcement of moral values, he offered one of the first purely secular moral theories, which grounded morality in the pleasing and useful consequences that result from our actions. He introduced the term “utility” into our moral vocabulary, and his theory is the immediate forerunner to the classic utilitarian views of Jeremy Bentham and John Stuart Mill. He is famous for the position that we cannot derive ought from is, the view that statements of moral obligation cannot simply be deduced from statements of fact. Some see Hume as an early proponent of the emotivist metaethical view that moral judgments principally express our feelings. He also made important contributions to aesthetic theory with his view that there is a uniform standard of taste within human nature, in political theory with his critique of social contractarianism, and economic theory with his anti-mercantilist views. As a philosophical historian, he defended the conservative view that British governments are best run through a strong monarchy.

Table of Contents1. Life2. Origin and Association of Ideas3. Epistemological Issues

a. Spaceb. Timec. Necessary Connection between Causes and Effectsd. External Objectse. Personal Identityf. Free Will2. Skepticism3. Theory of the Passions4. Religious Belief

a. Miraclesb. Psychology of Religious Beliefc. Arguments for God’s Existence2. Moral Theory3. Aesthetic, Political, and Economic Theory4. History and Philosophy5. References and Further Reading

a. Recent Editions of Hume’s Writingsb. Chronological List of Hume’s Publicationsc. Biographies, Letters, Manuscriptsd. Bibliographiese. Works on Hume

1. Life

David Hume was born in 1711 to a moderately wealthy family from Berwickshire Scotland, near Edinburgh. His background was politically Whiggish and religiously Calvinistic. As a child he faithfully attended the local Church of Scotland, pastored by his uncle. Hume was educated by his widowed mother until he left for the University of Edinburgh at the age of eleven. His letters describe how as a young student he took religion seriously and obediently followed a list of moral guidelines taken from The Whole Duty of Man, a popular Calvinistic devotional.

Leaving the University of Edinburgh around the age of fifteen to pursue his education privately, he was encouraged to consider a career in law, but his interests soon turned to philosophy. During these years of private study he began raising serious questions about religion, as he recounts in the following letter:

Tis not long ago that I burn’d an old Manuscript Book, wrote before I was twenty; which contain’d, Page after Page, the gradual Progress of my Thoughts on that head [i.e. religious belief]. It begun with an anxious Search after Arguments, to confirm the common Opinion: Doubts stole in, dissipated, return’d, were again dissipated, return’d again [To Gilbert Elliot of Minto, March 10, 1751].

Although his manuscript book was destroyed, several pages of his study notes survive from his early twenties. These show a preoccupation with proofs for God’s existence as well as atheism, particularly as he read on these topics in classical Greek and Latin texts and in Pierre Bayle’s skeptical Historical and Critical Dictionary. During these years of private study, some of which were in France, he composed his three-volume Treatise of Human Nature, which was published anonymously in two installments before he was thirty (1739, 1740). The Treatise explores several philosophical topics such as space, time, causality, external objects, the passions, free will, and morality, offering original and often skeptical appraisals of these notions. Book I of the Treatise was unfavorably reviewed in the History of the Works of the Learned with a succession of sarcastic comments. Although scholars today recognized it as a philosophical masterpiece, Hume was

disappointed with the minimal interest his book spawned and said that “It fell dead-born from the press, without reaching such distinctions even to excite a murmur among the zealots” (My Own Life).

In 1741 and 1742 Hume published his two-volume Essays, Moral and Political, which were written in a popular style and were more successful than the Treatise. In 1744-1745 he was a candidate for the Chair of Moral Philosophy at the University of Edinburgh. The Edinburgh Town Council was responsible for electing a replacement, and critics opposed Hume by condemning his anti-religious writings. Chief among the critics was clergyman William Wishart (d. 1752), the Principal of the University of Edinburgh. Lists of allegedly dangerous propositions from Hume’s Treatise circulated, presumably penned by Wishart himself. In the face of such strong opposition, the Edinburgh Town Council consulted the Edinburgh ministers. Hoping to win over the clergy, Hume composed a point by point reply to the circulating lists of dangerous propositions, which was published as A Letter from a Gentleman to his Friend in Edinburgh. The clergy were not swayed, 12 of the 15 ministers voted against Hume, and he quickly withdrew his candidacy. In 1745 Hume accepted an invitation from General St Clair to attend him as secretary. He wore the uniform of an officer, and accompanied the general on an expedition against Canada (which ended in an incursion on the coast of France) and to an embassy post in the courts of Vienna and Turin.

Because of the success of his Essays, Hume was convinced that the poor reception of his Treatise was caused by its style rather than by its content. In 1748 he published his Enquiry Concerning Human Understanding, a more popular rendition of portions of Book I of the Treatise. The Enquiry also includes two sections not found in the Treatise: “Of Miracles” and a dialogue titled “Of a Particular Providence and of a Future State.” Each section contains direct attacks on religious belief. In 1751 he published hisEnquiry Concerning the Principles of Morals, which recasts parts of Book III of the Treatise in a very different form. The work establishes a system of morality upon utility and human sentiments alone, and without appeal to divine moral commands. By the end of the century Hume was recognized as the founder of the moral theory of utility, and utilitarian political theorist Jeremy Bentham acknowledged Hume’s direct influence upon him. The same year Hume also published his Political Discourses, which drew immediate praise and influenced economic thinkers such as Adam Smith, William Godwin, and Thomas Malthus.

In 1751-1752 Hume sought a philosophy chair at the University of Glasgow, and was again unsuccessful. In 1752 his new employment as librarian of the Advocate’s Library in Edinburgh provided him with the resources to pursue his interest in history. There, he wrote much of his highly successful six-volumeHistory of England (published from 1754 to 1762). The first volume was unfavorably received, partially for its defense of Charles I, and partially for two sections which attack Christianity. In one passage Hume notes that the first Protestant reformers were fanatical or “inflamed with the highest enthusiasm” in their opposition to Roman Catholic domination. In the second passage he labels Roman Catholicism a superstition which “like all other species of superstition. . .  rouses the vain fears of unhappy mortals.” The most vocal attack against Hume’s History came from Daniel MacQueen in his 300 page Letters on Mr. Hume’s History. MacQueen scrutinizes the first volume of Hume’s work, exposing all the allegedly “loose and irreligious sneers” Hume makes against Christianity. Ultimately, this negative response led Hume to delete the two controversial passages from succeeding editions of the History.

Around this time Hume also wrote his two most substantial works on religion: The Dialogues Concerning Natural Religion and The Natural History of Religion. The Natural History appeared in 1757, but, on the advice of friends who wished to steer Hume away from religious controversy, the Dialogues remained unpublished until 1779, three years after his death. The Natural History aroused controversy even before it was made public. In 1756 a volume of Hume’s essays titled Five Dissertations was printed and ready for distribution. The essays included (1) “The Natural History of Religion;” (2) “Of the Passions;” (3) “Of Tragedy;” (4) “Of Suicide;” and (5) “Of the Immortality of the Soul.” The latter two essays made direct attacks on common religious doctrines by defending a person’s moral right to commit suicide and by criticizing the idea of life after death. Early copies were passed around, and Hume’s publisher was threatened with prosecution if the book was distributed as it was. The printed copies of Five Dissertationswere then physically altered by removing the essays on suicide and immortality, and inserting a new essay “Of the Standard of

Taste” in their place. Hume also took this opportunity to alter two particularly offending paragraphs in the Natural History. The essays were then bound with the new title Four Dissertations and distributed in January, 1757.

In the years following Four Dissertations, Hume completed his last major literary work, The History of England, which gave him a reputation as an historian that equaled, if not overshadowed, his reputation as a philosopher.  In 1763, at age 50, he was invited to accompany the Earl of Hertford to the embassy in Paris, with a near prospect of being his secretary. He eventually accepted, and remarks at the reception he received in Paris “from men and women of all ranks and stations.” He returned to Edinburgh in 1766, and continued developing relations with the greatest minds of the time. Among these was Jean Jacques Rousseau who in 1766 was ordered out of Switzerland by the government in Berne. Hume offered Rousseau refuge in England and secured him a government pension. In England, Rousseau became suspicious of plots, and publicly charged Hume with conspiring to ruin his character, under the appearance of helping him. Hume published a pamphlet defending his actions and was exonerated. Another secretary appointment took him away from 1767-1768. Returning again to Edinburgh, his remaining years were spent revising and refining his published works, and socializing with friends in Edinburgh’s intellectual circles. In 1770, fellow Scotsman James Beattie published one of the harshest attacks on Hume’s philosophy to ever appear in print, entitled An Essay on the Nature and Immutability of Truth in Opposition to Sophistry and Scepticism. Hume was upset by Beattie’s relentless verbal attacks against him in the work, but the book made Beattie famous and King George III, who admired it, awarded Beattie a pension of £200 per year.

In 1776, at age sixty-five, Hume died from an internal disorder which had plagued him for many months. After his death, his name took on new significance as several of his previously unpublished works appeared. The first was a brief autobiography, My Own Life, but even this unpretentious work aroused controversy. As his friends, Adam Smith and S.J. Pratt, published affectionate eulogies describing how he died with no concern for an afterlife, religious critics responded by condemning this unjustifiable admiration of Hume’s infidelity. Two years later, in 1779, Hume’s Dialogues Concerning Natural Religion appeared. Again, the response was mixed. Admirers of Hume considered it a masterfully written work, while religious critics branded it as dangerous to religion. Finally, in 1782, Hume’s two suppressed essays on suicide and immortality were published. Their reception was almost unanimously negative.

2. Origin and Association of Ideas

Drawing heavily on John Locke’s empiricism, the opening sections of both the Treatise and Enquirydiscuss the origins of mental perceptions as laid out in the following categorical scheme:

Perceptions

A. Ideas

1. From memory

2. From imagination

a. From fancy

b. From understanding

(1) Involving relations of ideas

(2) Involving matters of fact

B. Impressions

1. Of sensation (external)

2. Of reflection (internal)

Hume begins by dividing all mental perceptions between ideas (thoughts) and impressions (sensations and feelings), and then makes two central claims about the relation between them. First, advancing what is commonly called Hume’s copy thesis, he argues that all ideas are ultimately copied from impressions. That is, for any idea we select, we can trace the component parts of that idea to some external sensation or internal feeling. This claim places Hume squarely in the empiricist tradition, and he regularly uses this principle as a test for determining the content of an idea under consideration. As proof of the copy thesis, Hume challenges anyone who denies it “to shew a simple impression, that has not a correspondent idea, or a simple idea, that has not a correspondent impression” (Treatise, 1.1.1). Second, advancing what we may call Hume’s liveliness thesis, he argues that ideas and impressions differ only in terms of liveliness. For example, my impression of a tree is simply more vivid than my idea of that tree. One of his early critics, Lord Monboddo (1714–1799) pointed out an important implication of the liveliness thesis, which Hume himself presumably hides. Most modern philosophers held that ideas reside in our spiritual minds, whereas impressions originate in our physical bodies. So, when Hume blurs the distinction between ideas and impressions, he is ultimately denying the spiritual nature of ideas and instead grounding them in our physical nature. In short, all of our mental operations—including our most rational ideas—are physical in nature. As Monboddo writes, “One consequence, which Mr Hume has drawn from this doctrine, is, that, as our Mind can only operate by the organs of the Body, it must perish with the Body” (Ancient Metaphysics, 1782, 2.2.2).

Hume goes on to explain that there are several mental faculties that are responsible for producing our various ideas. He initially divides ideas between those produced by the memory, and those produced by the imagination. The memory is a faculty that conjures up ideas based on experiences as they happened. For example, the memory I have of my drive to the store is a comparatively accurate copy of my previous sense impressions of that experience. The imagination, by contrast, is a faculty that breaks apart and combines ideas, thus forming new ones. Hume uses the familiar example of a golden mountain: this idea is a combination of an idea of gold and an idea of a mountain. As our imagination takes our most basic ideas and leads us to form new ones, it is directed by three principles of association, namely,resemblance, contiguity, and cause and effect. By virtue of resemblance, an illustration or sketch, of a person leads me to an idea of that actual person. The idea of one apartment in a building leads me to think of the apartment contiguous to—or next to—the first. The thought of a scar on my hand leads me to think of a broken piece of glass that caused the scar.

As indicated in the above chart, our more complex ideas of the imagination are further divided between two categories. Some imaginative ideas represent flights of the fancy, such as the idea of a golden mountain; however, other imaginative ideas represent solid reasoning, such as predicting the trajectory of a thrown ball. The fanciful ideas are derived from the faculty of the fancy, and are the source of fantasies, superstitions, and bad philosophy. By contrast, sound ideas are derived from the faculty of theunderstanding—or reason—and are of two types: (1) involving relations of ideas; or (2) involving matters of fact. A relation of ideas (or relation between ideas) is a mathematical relation that is “discoverable by the mere operation of thought, without dependence on what is anywhere existent in the universe,” such as the mathematical statement “the square of the hypotenuse is equal to the square of the two sides” (Enquiry, 4). By contrast, a matter of fact, for Hume, is any object or circumstance which has physical existence, such as “the sun will rise tomorrow”. This split between relations of ideas and matters of fact is commonly called “Hume’s Fork”, and Hume himself uses it as a radical tool for distinguishing between well-founded ideas of the understanding, and unfounded ideas of the fancy. He dramatically makes this point at the conclusion of his Enquiry:

When we run over libraries, persuaded of these principles, what havoc must we make? If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning

concerning matter of fact and existence? No. Commit it then to the flames: For it can contain nothing but sophistry and illusion (Enquiry, 12).

For Hume, when we imaginatively exercise our understanding regarding relations of ideas and matters of fact, our minds are guided by seven philosophical or “reasoning” relations, which are as follows:

Principles of reasoning concerning relations of ideas (involving demonstration): (1) resemblance; (2) contrariety; (3) degrees in quality; and (4) proportions in quantity or number

Principles of reasoning concerning matters of fact (involving judgments of probability): (5) identity; (6) relations in time and place; and (7) causation

Human understanding and reasoning at its best, then, involves ideas that are grounded in the above seven principles.

3. Epistemological Issues

Much of Hume’s epistemology is driven by a consideration of philosophically important issues, such as space and time, cause-effect, external objects, personal identity, and free will. In his analysis of these issues in the Treatise, he repeatedly does three things. First, he skeptically argues that we are unable to gain complete knowledge of some important philosophical notion under consideration. Second, he shows how the understanding gives us a very limited idea of that notion. Third, he explains how some erroneous views of that notion are grounded in the fancy, and he accordingly recommends that we reject those erroneous ideas. We will follow this three-part scheme as we consider Hume’s discussions of various topics.

a. Space

On the topic of space, Hume argues that our proper notions of space are confined to our visual and tactile experiences of the three-dimensional world, and we err if we think of space more abstractly and independently of those visual and tactile experiences. In essence, our proper notion of space is like what Locke calls a “secondary quality” of an object, which is spectator dependent, meaning grounded in the physiology of our perceptual mental processes. Thus, our proper notion of space is not like a “primary quality” that refers to some external state of affairs independent of our perceptual mental process. Following the above three-part scheme, (1) Hume skeptically argues that we have no ideas of infinitely divisible space (Treatise, 1.2.2.2). (2) When accounting for the idea we do have of space, he argues that “the idea of space is convey’d to the mind by two senses, the sight and touch; nor does any thing ever appear extended, that is not either visible or tangible” (Treatise, 1.2.3.15). Further, he argues that these objects—which are either visible or tangible—are composed of finite atoms or corpuscles, which are themselves “endow’d with colour and solidity.” These impressions are then “comprehended” or conceived by the imagination; it is from the structuring of these impressions that we obtain a limited idea of space. (3) In contrast to this idea of space, Hume argues that we frequently presume to have an idea of space that lacks visibility or solidity. He accounts for this erroneous notion in terms of a mistaken association that people naturally make between visual and tactile space (Treatise, 1.2.5.21).

b. Time

Hume’s treatment of our idea of time is like his treatment of the idea of space, in that our proper idea of time is like a secondary quality, grounded in our mental operations, not a primary quality

grounded in some external phenomenon beyond our experience. (1) He first maintains that we have no idea of infinitely divisible time (Treatise, 1.2.4.1). (2) He then notes Locke’s point that our minds operate at a range of speeds that are “fix’d by the original nature and constitution of the mind, and beyond which no influence of external objects on the senses is ever able to hasten or retard our thought” (Treatise, 1.2.3.7). The idea of time, then, is not a simple idea derived from a simple impression; instead, it is a copy of impressions as they are perceived by the mind at its fixed speed (Treatise, 1.2.3.10). (3) In contrast to this limited view of time, he argues that we frequently entertain a faulty notion of time that does not involve change or succession. The psychological account of this erroneous view is that we mistake time for the cause of succession instead of seeing it as the effect (Treatise, 1.2.5.29).

c. Necessary Connection between Causes and Effects

According to Hume, the notion of cause-effect is a complex idea that is made up of three more foundational ideas: priority in time, proximity in space, and necessary connection. Concerning priority in time, if I say that event A causes event B, one thing I mean is that A occurs prior to B. If B were to occur before A, then it would be absurd to say that A was the cause of B. Concerning the idea of proximity, if I say that A causes B, then I mean that B is in proximity to, or close to A. For example, if I throw a rock, and at that moment someone’s window in China breaks, I would not conclude that my rock broke a window on the other side of the world. The broken window and the rock must be in proximity with each other. Priority and proximity alone, however, do not make up our entire notion of causality. For example, if I sneeze and the lights go out, I would not conclude that my sneeze was the cause, even though the conditions of priority and proximity were fulfilled. We also believe that there is a necessary connection between cause A and effect B. During the modern period of philosophy, philosophers thought of necessary connection as a power or force connecting two events. When billiard ball A strikes billiard ball B, there is a power that the one event imparts to the other. In keeping with his empiricist copy thesis, that all ideas are copied from impressions, Hume tries to uncover the experiences which give rise to our notions of priority, proximity, and necessary connection. The first two are easy to explain. Priority traces back to our various experiences of time. Proximity traces back to our various experiences of space. But what is the experience which gives us the idea of necessary connection? This notion of necessary connection is the specific focus of Hume’s analysis of cause-effect.

Hume’s view is that our proper idea of necessary connection is like a secondary quality that is formed by the mind, and not, like a primary quality, a feature of the external world. (1) He skeptically argues that we cannot get an idea of necessary connection by observing it through sensory experiences (Treatise, 1.3.14.12 ff.). We have no external sensory impression of causal power when we observe cause-effect relationships; all that we ever see is cause A constantly conjoined with effect B. Neither does it arise from an internal impression, such as when we introspectively reflect on willed bodily motions or willing the creation of thoughts. These internal experiences are too elusive, and nothing in them can give content to our idea of necessary connection. (2) The idea we have of necessary connection arises as follows: we experience a constant conjunction of events A and B— repeated sense experiences where events resembling A are always followed by events resembling B. This produces a habit such that upon any further appearance of A, we expect B to follow. This, in turn, produces an internal feeling of expectation “to pass from an object to the idea of its usual attendant,” which is the impression from which the idea of necessary connection is copied (Treatise, 1.3.14.20). (3) A common but mistaken notion on this topic is that necessity resides within the objects themselves. He explains this mistaken belief by the natural tendency we have to impute subjectively perceived qualities to external things (Treatise, 1.3.14.24).

d. External Objects

Hume’s view on external objects is that the mind is programmed to form some concept of the external world, although this concept or idea is really just a fabrication. (1) Hume’s skeptical claim here is that we have no valid conception of the existence of external things (Treatise, 1.2.6.9). (2) Nevertheless, he argues that we have an unavoidable “vulgar” or common belief in the continued existence of objects, and this idea he accounts for. His explanation is lengthy, but involves the following features. Perceptions of objects are disjointed and have no unity in and of themselves (Treatise, 1.4.2.29). In an effort to organize our perceptions, we first naturally assume that there is no distinction between our perceptions and the objects that are perceived (this is the so-called “vulgar” view of perception). We then conflate all ideas (of perceptions), which put our minds in similar dispositions (Treatise, 1.4.2.33); that is, we associate resembling ideas and attribute identity to their causes. Consequently, we naturally invent the continued and external existence of the objects (or perceptions) that produced these ideas (Treatise, 1.4.2.35). Lastly, we go on to believe in the existence of these objects because of the force of the resemblance between ideas (Treatise, 1.4.2.36). Although this belief is philosophically unjustified, Hume feels he has given an accurate account of how we inevitably arrive at the idea of external existence. (3) In contrast to the previous explanation of this idea, he recommends that we doubt a more sophisticated but erroneous notion of existence—the so-called philosophical view—which distinguishes between perceptions and the external objects that cause perceptions. The psychological motivation for accepting this view is this: our imagination tells us that resembling perceptions have a continued existence, yet our reflection tells us that they are interrupted. Appealing to both forces, we ascribe interruption to perceptions and continuance to objects (Treatise, 1.4.2.52).

e. Personal Identity

Regarding the issue of personal identity, (1) Hume’s skeptical claim is that we have no experience of a simple, individual impression that we can call the self—where the “self” is the totality of a person’s conscious life. He writes, “For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe anything but the perception” (Treatise, 1.4.6.3). (2) Even though my perceptions are fleeting and I am a bundle of different perceptions, I nevertheless have some idea of personal identity, and that must be accounted for (Treatise, 1.4.6.4). Because of the associative principles, the resemblance or causal connection within the chain of my perceptions gives rise to an idea of myself, and memory extends this idea past my immediate perceptions (Treatise, 1.4.6.18 ff.). (3) A common abuse of the notion of personal identity occurs when the idea of a soul or unchanging substance is added to give us a stronger or more unified concept of the self (Treatise, 1.4.6.6).

f. Free Will

On the issue of free will and determinism—or “liberty” and “necessity” in Hume’s terminology—Hume defends necessity. (1) He first argues that “all actions of the will have particular causes” (Treatise,2.3.2.8), and so there is no such thing as an uncaused willful action. (2) He then defends the notion of a will that consistently responds to prior motivational causes: “our actions have a constant union with our motives, tempers, and circumstances” (Treatise, 2.3.1.4). These motives produce actions that have the same causal necessity observed in cause-effect relations that we see in external objects, such as when billiard ball A strikes and moves billiard ball B. In the same way, we regularly observe the rock-solid connection between motive A and action B, and we rely on that predictable connection in our normal lives. Suppose that a traveler, in recounting his observation of the odd behavior of natives in a distant country, told us that identical motives led to entirely different actions among these natives.  We would not believe the traveler’s report. In business, politics, and military affairs, our leaders expect predicable behavior from us insofar as the same motives within us will always result in us performing the same action. A prisoner who is soon to be executed will assume that the motivations and actions of the prison guards and the executioner are so rigidly fixed that these people will mechanically carry out their duties and perform the execution, with no chance of a change of heart (Treatise, 2.3.1.5 ff.).  (3) Lastly, Hume explains why people

commonly believe in an uncaused will (Treatise, 2.3.2.1 ff.). One explanation is that people erroneously believe they have a feeling of liberty when performing actions. The reason is that, when we perform actions, we feel a kind of “looseness or indifference” in how they come about, and some people wrongly see this as “an intuitive proof of human liberty” (Treatise, 2.3.2.2).

In the Treatise Hume rejects the notion of liberty completely. While he gives no definition of “liberty” in that work, he argues that the notion is incompatible with necessity, and, at best, “liberty” simply means chance. In the Enquiry, however, he takes a more compatiblist approach. All human actions are caused by specific prior motives, but liberty and necessity are reconcilable when we define liberty as “a power of acting or not acting, according to the determinations of the will” (Enquiry, 8). Nothing in this definition of liberty is in conflict with the notion of necessity.

4. Skepticism

In all of the above discussions on epistemological topics, Hume performs a balancing act between making skeptical attacks (step 1) and offering positive theories based on natural beliefs (step 2). In the conclusion to Book 1, though, he appears to elevate his skepticism to a higher level and exposes the inherent contradictions in even his best philosophical theories. He notes three such contradictions. One centers on what we call induction. Our judgments based on past experience all contain elements of doubt; we are then impelled to make a judgment about that doubt, and since this judgment is also based on past experience it will in turn produce a new doubt. Once again, though, we are impelled to make a judgment about this second doubt, and the cycle continues. He concludes that “no finite object can subsist under a decrease repeated in infinitum.” A second contradiction involves a conflict between two theories of external perception, each of which our natural reasoning process leads us to.  One is our natural inclination to believe that we are directly seeing objects as they really are, and the other is the more philosophical view that we only ever see mental images or copies of external objects. The third contradiction involves a conflict between causal reasoning and belief in the continued existence of matter. After listing these contradictions, Hume despairs over the failure of his metaphysical reasoning:

The intense view of these manifold contradictions and imperfections in human reason has so wrought upon me, and heated my brain, that I am ready to reject all belief and reasoning, and can look upon no opinion even as more probable or likely than another [Treatise, 1.4.7.8].

He then pacifies his despair by recognizing that nature forces him to set aside his philosophical speculations and return to the normal activities of common life. He sees, though, that in time he will be drawn back into philosophical speculation in order to attack superstition and educate the world.

Hume’s emphasis on these conceptual contradictions is a unique aspect of his skepticism, and if any part of his philosophy can be designated “Humean skepticism” it is this.  However, during the course of his writing the Treatise his view of the nature of these contradictions changed. At first he felt that these contradictions were restricted to theories about the external world, but theories about the mind itself would be free from them, as he explains here:

The essence and composition of external bodies are so obscure, that we must necessarily, in our reasonings, or rather conjectures concerning them, involve ourselves in contradictions and absurdities. But as the perceptions of the mind are perfectly known, and I have us’d all imaginable caution in forming conclusions concerning them, I have always hop’d to keep clear of those contradictions, which have attended every other system [Treatise, 2.2.6.2].

When composing the Appendix to the Treatise a year later, he changed his mind and felt that theories about the mind would also have contradictions:

I had entertained some hopes, that however deficient our theory of the intellectual world might be, it wou’d be free from those contradictions, and absurdities, which seem to attend every explication, that human reason can give of the material world. But upon a more strict review of the section

concerning I find myself involv’d in such a labyrinth, that, I must confess, I neither know how to correct my former opinions, nor how to render them consistent. If this be not a good general reason for scepticism, ’tis at least a sufficient one (if I were not already abundantly supplied) for me to entertain a diffidence and modesty in all my decisions [Treatise, Appendix].

Thus, in the Treatise, the skeptical bottom line is that even our best theories about both physical and mental phenomena will be plagued with contradictions. In the concluding section of his Enquiry, Hume again addresses the topic of skepticism, but treats the matter somewhat differently: he rejects extreme skepticism but accepts skepticism in a more moderate form. He associates extreme Pyrrhonian   skepticismwith blanket attacks on all reasoning about the external world, abstract reasoning about space and time, or causal reasoning about matters of fact. He argues, though, that we must reject such skepticism since “no durable good can ever result from it.” Instead, he recommends a more moderate or Academicskepticism that tones down Pyrrhonism by, first, exercising caution and modesty in our judgments, and, second,  by restricting our speculations to abstract reasoning and matters of fact.

5. Theory of the Passions

Like many philosophers of his time, Hume developed a theory of the passions—that is, the emotions—categorizing them and explaining the psychological mechanisms by which they arise in the human mind. His most detailed account is in Book Two of the Treatise. Passions, according to Hume, fall under the category of impressions of reflection (as opposed to impressions of sensation). He opens his discussion with a taxonomy of types of passions, which are outlined here:

Reflective Impressions

1. Calm (reflective pleasures and pains)

2. Violent

a. Direct (desire, aversion, joy, grief, hope, fear)

b. Indirect (love, hate, pride, humility)

He initially divides passions between the calm and the violent. He concedes that this distinction is imprecise, but he explains that people commonly distinguish between types of passions in terms of their degrees of forcefulness. Adding more precision to this common distinction, he maintains that calm passions are emotional feelings of pleasure and pain associated with moral and aesthetic judgments. For example, when I see a person commit a horrible deed, I will experience a feeling of pain. When I view a good work of art, I will experience a feeling of pleasure. In contrast to the calm passions, violent ones constitute the bulk of our emotions, and these divide between direct and indirect passions. For Hume, the key direct passions are desire, aversion, joy, grief, hope, and fear.  They are called “direct” because they arise immediately—without complex reflection on our part—whenever we see something good or bad. For example, if I consider an unpleasant thing, such as being burglarized, then I will feel the passion of aversion. He suggests that sometimes these passions are sparked instinctively—for example, by  my desire for food when I am hungry. Others, though, are not connected with instinct and are more the result of social conditioning. There is an interesting logic to the six direct passions, which Hume borrowed from a tradition that can be traced to ancient Greek Stoicism. We can diagram the relation between the six with this chart:

When good/bad objects are considered abstractly

Desire (towards good objects)

Aversion (towards evil objects)

When good/bad objects are actually present

Joy (towards good objects)

Grief (towards evil objects)

When good/bad objects are only anticipated

Hope (towards good objects)

Fear (towards evil objects)

Compare, for example, the passions that I will experience regarding winning the lottery vs. having my house burglarized. Suppose that I consider them purely in the abstract—or “consider’d simply” as Hume says (Treatise, 2.3.9.6). I will then desire to win the lottery and have an aversion towards being burglarized. Suppose that both situations are actually before me; I will then experience joy over winning the lottery and grief over being burglarized. Suppose, finally, that I know that at some unknown time in the future I will win the lottery and be burglarized. I will then experience hope regarding the lottery and fear of being burglarized.

Hume devotes most of Book 2 to an analysis of the indirect passions, his unique contribution to theories of the passions. The four principal passions are love, hate, pride, and humility. They are called “indirect” since they are the secondary effects of a previous feeling of pleasure and pain. Suppose, for example, that I paint a picture, which gives me a feeling of pleasure. Since I am the artist, I will then experience an additional feeling of pride. He explains in detail the psychological process that triggers indirect passions such as pride. Specifically, he argues that these passions arise from a double relation between ideas and impressions, which we can illustrate here with the passion of pride:

1. I have an initial idea of some possession, or “subject”, such as my painting, and this idea gives me pleasure.

2. Through the associative principle of resemblance, I then immediately associate this feeling of pleasure with a resembling feeling of pride (this association constitutes the first relation in the double relation).

3. This feeling of pride then causes me to have an idea of myself, as the “object” of pride.

4. Through some associative principle such as causality, I then associate the idea of myself with the idea of my painting, which is the “subject” of my pride (this association constitutes the second relation in the double relation).

According to Hume, the three other principal indirect passions arise in parallel ways. For example, if my painting is ugly and causes me pain, then I will experience the secondary passion of humility—perhaps more accurately expressed as “humiliation”. By contrast, if someone else paints a pleasing picture, then this will trigger in me a feeling of love for that artist—perhaps more accurately expressed as “esteem”. If the artist paints a painfully ugly picture, then this will trigger in me a feeling of “hatred” towards the artist—perhaps more accurately expressed as “disesteem”.

One of the most lasting contributions of Hume’s discussion of the passions is his argument that human actions must be prompted by passion, and never can be motivated by reason. Reason, he argues, is completely inert when it comes to motivating conduct, and without some emotion we

would not engage in any action. Thus, he writes, “Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them” (Treatise, 2.3.3.4).

6. Religious Belief

Like many of Hume’s philosophical views, his position on religious belief is also skeptical. Critics of religion during the eighteenth-century needed to express themselves cautiously to avoid being fined, imprisoned, or worse. Sometimes this involved placing controversial views in the mouth of a character in a dialogue. Other times it involved adopting the persona of a deist or fideist as a means of concealing a more extreme religious skepticism. Hume used all of the rhetorical devices at his disposal, and left it to his readers to decode his most controversial conclusions on religious subjects. During the Enlightenment, there were two pillars of traditional Christian belief: natural and revealed religion. Natural religioninvolves knowledge of God drawn from nature through the use of logic and reason, and typically involves logical proofs regarding the existence and nature of God, such as the causal and design arguments for God’s existence. Revealed religion involves knowledge of God contained in revelation, particularly the Bible, the quintessential examples of which are biblical prophesies and miracles where God intervenes in earthly affairs to confirm the Bible’s message of salvation. Hume attacks both natural and revealed religious beliefs in his various writings.

a. Miracles

In a 1737 letter to Henry Home, Hume states that he intended to include a discussion of miracles in hisTreatise, but ultimately left it out for fear of offending readers. His analysis of the subject eventually appeared some ten years later in his essay “Of Miracles” from the Enquiry, and is his first sustained attack on revealed religion. It is probably this main argument to which Hume refers. The first of this two-part essay contains the argument for which Hume is most famous: uniform experience of natural law outweighs the testimony of any alleged miracle. Let us imagine a scale with two balancing pans. In the first pan we place the strongest evidence in support of the occurrence of a miracle. In the second we place our life-long experience of consistent laws of nature. According to Hume, the second pan will always outweigh the first. He writes:

It is experience only, which gives authority to human testimony [regarding miracles]; and it is the same experience, which assures us of the laws of nature. When, therefore, these two kinds of experience are contrary, we have nothing to do but subtract the one from the other, and embrace an opinion, either on one side or the other, with that assurance which arises from the remainder. But according to the principle here explained, this subtraction, with regard to all popular religions, amounts to an entire annihilation [Enquiry, 10.1].

Regardless of how strong the testimony is in favor of a given miracle, it can never come close to counterbalancing the overwhelming experience of unvaried laws of nature. Thus, proportioning one’s belief to the evidence, the wise person must reject the weaker evidence concerning the alleged miracle.

In the second part of “Of Miracles”, Hume discusses four factors that count against the credibility of most miracle testimonies: (1) witnesses of miracles typically lack integrity; (2) we are naturally inclined to enjoy sensational stories, and this has us uncritically perpetuate miracle accounts; (3) miracle testimonies occur most often in less civilized countries; and (4) miracles support rival religious systems and thus discredit each other. But even if a miracle testimony is not encumbered by these four factors, we should still not believe it since it would be contrary to our consistent experience of laws of nature. He concludes his essay with the following cryptic comment about Christian belief in biblical miracles:

upon the whole, we may conclude, that the Christian Religion not only was at first attended with miracles, but even at this day cannot be believed by any reasonable person without one. Mere reason is insufficient to convince us of its veracity: And whoever is moved by Faith to assent to it, is conscious of a continued miracle in his own person, which subverts all the principles of his understanding, and gives him a determination to believe what is most contrary to custom and experience [Enquiry, 10.2].

At face value, his comment suggests a fideist approach to religious belief such as what Pascal recommends. That is, reason is incapable of establishing religious belief, and God must perform a miracle in our lives to make us open to belief through faith. However, according to the eighteenth-century Hume critic John Briggs, Hume’s real point is that belief in Christianity requires “miraculous stupidity” (The Nature of Religious Zeal, 1775).

b. Psychology of Religious Belief

Another attack on revealed religion appears in Hume’s essay “The Natural History of Religion” (1757). It is one of the first systematic attempts to explain the causes of religious belief solely in terms of psychological and sociological factors. We might see the “Natural History” as an answer to a challenge, such as the sort that William Adams poses here in his attack on Hume’s “Of Miracles”:

Whence could the religion and laws of this people [i.e., the Jews] so far exceed those of the wisest Heathens, and come out at once, in their first infancy, thus perfect and entire; when all human systems are found to grow up by degrees, and to ripen, after many improvements; into perfection [An Essay, Part 2]?

According to Adams, only divine intervention can account for the sophistication of the ancient Jewish religion. In the “Natural History,” though, Hume offers an alternative explanation, and one that is grounded solely in human nature, without God’s direct involvement in human history.

The work may be divided into three parts. In the first (Sections 1 and 4), Hume argues that polytheism, and not monotheism, was the original religion of primitive humans. Monotheism, he believes, was only a later development that emerged with the progress of various societies. The standard theory in Judeo-Christian theology was that early humans first believed in a single God, but as religious corruption crept in, people lapsed into polytheism. Hume was the first writer to systematically defend the position of original polytheism. In the second part (Sections 2-3, 5-8), Hume establishes the psychological principles that give rise to popular religious belief. His thesis is that natural instincts—such as fear and the propensity to adulate—are the true causes of popular religious belief, and not divine intervention or rational argument. The third part of this work (Sections 9-15) compares various aspects of polytheism with monotheism, showing that one is no more superior than the other. Both contain points of absurdity. From this he concludes that we should suspend belief on the entire subject of religious truth.

c. Arguments for God’s Existence

Around the same time that Hume was composing his “Natural History of Religion” he was also working on his Dialogues Concerning Natural Religion, which appeared in print two decades later, after his death. As the title of the work implies, it is a critique of natural religion, in contrast with revealed religion. There are three principal characters in the Dialogues. A character named Cleanthes, who espouses religious empiricism, defends the design argument for God’s existence, but rejects the causal argument. Next, a character named Demea, who is a religious rationalist, defends the causal argument for God’s existence, but rejects the design argument. Finally, a character named Philo, who is a religious skeptic, argues against both the design and causal arguments. The

main assaults on theistic proofs are conveyed by both Cleanthes and Philo, and, to that extent, both of their critiques likely represent Hume’s views.

The specific version of the causal argument that Hume examines is one by Samuel Clarke (and Leibniz before him). Simplistic versions of the causal argument maintain that when we trace back the causes of things in the universe, the chain of causes cannot go back in time to infinity past; there must be a first cause to the causal sequence, which is God. Clarke’s version differs in that it is theoretically possible for causal sequences of events to trace back through time to infinity past. Thus, we cannot argue that God’s existence is required to initiate a sequence of temporal causes. Nevertheless, Clarke argued, an important fact still needs to be explained: the fact that this infinite temporal sequence of causal events exists at all. Why does something exist rather than nothing? God, then, is the necessary cause of the whole series. In response, the character Cleanthes argues that the flaw in the cosmological argument consists in assuming that there is some larger fact about the universe that needs explaining beyond the particular items in the series itself. Once we have a sufficient explanation for each particular fact in the infinite sequence of events, it makes no sense to inquire about the origin of the collection of these facts. That is, once we adequately account for each individual fact, this constitutes a sufficient explanation of the whole collection. He writes, “Did I show you the particular causes of each individual in a collection of twenty particles of matter, I should think it very unreasonable, should you afterwards ask me, what was the cause of the whole twenty” (Dialogues, 9).

The design argument for God’s existence is that the appearance of design in the natural world is evidence for the existence of a divine designer. The specific version of the argument that Hume examines is one from analogy, as stated here by Cleanthes:

The curious adapting of means to ends, throughout all nature, resembles exactly, though it much exceeds, the productions of human contrivance; of human designs, thought, wisdom, and intelligence. Since, therefore, the effects resemble each other, we are led to infer, by all the rules of analogy, that the causes also resemble; and that the Author of Nature is somewhat similar to the mind of man (Dialogues, 2).

Philo presents several criticisms against the design argument, many of which are now standard in discussions of the issue. According to Philo, the design argument is based on a faulty analogy: we do not know whether the order in nature was the result of design, since, unlike our experience with the creation of machines, we did not witness the formation of the world. In Philo’s words, “will any man tell me with a serious countenance, that an orderly universe must arise from some thought and art like the human, because we have experience of it? To ascertain this reasoning, it were requisite that we had experience of the origin of worlds; and it is not sufficient, surely, that we have seen ships and cities arise from human art and contrivance” (ibid). Further, the vastness of the universe also weakens any comparison with human artifacts. Although the universe is orderly here, it may be chaotic elsewhere. Similarly, if intelligent design is exhibited only in a small fraction of the universe, then we cannot say that it is the productive force of the whole universe. Philo states that “A very small part of this great system, during a very short time, is very imperfectly discovered to us; and do we thence pronounce decisively concerning the origin of the whole?” (ibid). Philo also argues that natural design may be accounted for by nature alone, insofar as matter may contain within itself a principle of order, and “This at once solves all difficulties” (Dialogues, 6). And even if the design of the universe is of divine origin, we are not justified in concluding that this divine cause is a single, all powerful, or all good being. According to Philo, “Whether all these attributes are united in one subject, or dispersed among several independent beings, by what phenomena in nature can we pretend to decide the controversy?” (Dialogues 5).

7. Moral Theory

Hume’s moral theory appears in Book 3 of the Treatise and in An Enquiry Concerning the Principles of Morals (1751). He opens his discussion in the Treatise by telling us what moral approval is not: it is not a rational judgment about either conceptual relations or empirical facts. To make his case he

criticizes Samuel Clarke’s rationalistic account of morality, which is that we rationally judge the fitness or unfitness of our actions in reference to eternal laws of righteousness, that are self-evidently known to all humans, just as is our knowledge of mathematical relations. Hume presents several arguments against Clarke’s view, one of which is an analogy from arboreal parricide: a young tree that overgrows and kills its parent exhibits the same alleged relations as a human child killing his parent. “Is not the one tree the cause of the other’s existence; and the latter the cause of the destruction of the former, in the same manner as when a child murders his parent?” (Treatise, 3.1.1.24). If morality is a question of relations, then the young tree is immoral, which is absurd. Hume also argues that moral assessments are not judgments about empirical facts. Take any immoral action, such as willful murder: “examine it in all lights, and see if you can find that matter of fact, or real existence, which you call vice” (Treatise, 3.1.1.25). You will not find any such fact, but only your own feelings of disapproval. In this context Hume makes his point that we cannot derive statements of obligation from statements of fact. When surveying various moral theories, Hume writes, “I am surpriz’d to find, that instead of the usual copulations of propositions, is, and is not, I meet with no proposition that is not connected with an ought or an ought not” (Treatise, 3.1.1.26). This move from is to ought is illegitimate, he argues, and is why people erroneously believe that morality is grounded in rational judgments.

Thus far Hume has only told us what moral approval is not, namely a judgment of reason. So what then does moral approval consist of? It is an emotional response, not a rational one. The details of this part of his theory rest on a distinction between three psychologically distinct players: the moral agent, the receiver, and the moral spectator. The moral agent is the person who performs an action, such as stealing a car; the receiver is the person impacted by the conduct, such as the owner of the stolen car; and the moral spectator is the person who observes and, in this case, disapproves of the agent’s action. This agent-receiver-spectator distinction is the product of earlier moral sense theories championed by the Earl of Shaftesbury (1671-1713), Joseph Butler (1692-1752), and Francis Hutcheson (1694-1747). Most generally, moral sense theories maintained that humans have a faculty of moral perception, similar to our faculties of sensory perception. Just as our external senses detect qualities in external objects, such as colors and shapes, so too does our moral faculty detect good and bad moral qualities in people and actions.

For Hume, all actions of a moral agent are motivated by character traits, specifically either virtuous or vicious character traits. For example, if you donate money to a charity, then your action is motivated by a virtuous character trait. Hume argues that some virtuous character traits are instinctive or natural, such as benevolence, and others are acquired or artificial, such as justice. As an agent, your action will have an effect on a receiver. For example, if you as the agent give food to a starving person, then the receiver will experience an immediately agreeable feeling from your act. Also, the receiver may see the usefulness of your food donation, insofar as eating food will improve his health. When considering the usefulness of your food donation, then, the receiver will receive another agreeable feeling from your act. Finally, I, as a spectator, observe these agreeable feelings that the receiver experiences. I, then, will sympathetically experience agreeable feelings along with the receiver. These sympathetic feelings of pleasure constitute my moral approval of the original act of charity that you, the agent, perform. By sympathetically experiencing this pleasure, I thereby pronounce your motivating character trait to be a virtue, as opposed to a vice. Suppose, on the other hand, that you as an agent did something to hurt the receiver, such as steal his car. I as the spectator would then sympathetically experience the receiver’s pain and thereby pronounce your motivating character trait to be a vice, as opposed to a virtue.

In short, that is Hume’s overall theory. There are, though, some important details that should also be mentioned. First, it is tricky to determine whether an agent’s motivating character trait is natural or artificial, and Hume decides this one virtue at a time. For Hume, the natural virtues include benevolence, meekness, charity, and generosity. By contrast, the artificial virtues include justice, keeping promises, allegiance and chastity. Contrary to what one might expect, Hume classifies the key virtues that are necessary for a well-ordered state as artificial, and he classifies only the more supererogatory virtues as natural. Hume’s critics were quick to point out this paradox. Second, to spark a feeling of moral approval, the spectator does not have to actually witness the effect of an agent’s action upon a receiver. The spectator might simply hear about it, or the spectator might even simply invent an entire scenario and think about the possible effects of hypothetical actions.

This happens when we have moral reactions when reading works of fiction: “a very play or romance may afford us instances of this pleasure, which virtue conveys to us; and pain, which arises from vices” (Treatise, 3.1.2.2).

Third, although the agent, receiver, and spectator have psychologically distinct roles, in some situations a single person may perform more than one of these roles. For example, if I as an agent donate to charity, as a spectator to my own action I can also sympathize with the effect of my donation on the receiver. Finally, given various combinations of spectators and receivers, Hume concludes that there are four irreducible categories of qualities that exhaustively constitute moral virtue: (1) qualities useful to others, which include benevolence, meekness, charity, justice, fidelity and veracity; (2) qualities useful to oneself, which include industry, perseverance, and patience; (3) qualities immediately agreeable to others, which include wit, eloquence and cleanliness; and (4) qualities immediately agreeable to oneself, which include good humor, self-esteem and pride. For Hume, most morally significant qualities and actions seem to fall into more than one of these categories. When Hume spoke about an agent’s “useful” consequences, he often used the word “utility” as a synonym. This is particularly so in the Enquiry Concerning the Principles of Morals where the term “utility” appears over 50 times. Moral theorists after Hume thus depicted his moral theory as the “theory of utility”—namely, that morality involves assessing the pleasing and painful consequences of actions on the receiver. It is this concept and terminology that inspired classic utilitarian philosophers, such as Jeremy Bentham (1748–1832).

8. Aesthetic, Political, and Economic Theory

Hume wrote two influential essays on the subject of aesthetic theory. In “Of Tragedy” (1757) he discusses the psychological reasons why we enjoy observing depictions of tragic events in theatrical production. He argues that “the energy of expression, the power of numbers, and the charm of imitation” convey the sense of pleasure. He particularly stresses the technical artistry involved when an artistic work imitates the original. In “Of the Standard of Taste” (1757) he argues that there is a uniform sense of artistic judgment in human nature, similar to our uniform sense of moral judgment. Specific objects consistently trigger feelings of beauty within us, as our human nature dictates. Just as we can refine our external senses such as our palate, we can also refine our sense of artistic beauty and thus cultivate a delicacy of taste. In spite of this uniform standard of taste, two factors create some difference in our judgments: “the one is the different humours of particular men; the other, the particular manners and opinions of our age and country.”

In political theory, Hume has both theoretical discussions on the origins of government and more informal essays on popular political controversies of his day. In his theoretical discussions, he attacks two basic notions in eighteenth-century political philosophy: the social contract and the instinctive nature of justice regarding private property. In his 1748 essay “Of the Original Contract,” he argues that political allegiance is not grounded in any social contract, but instead on our general observation that society cannot be maintained without a governmental system. He concedes that in savage times there may have been an unwritten contract among tribe members for the sake of peace and order. However, he argues, this was no permanent basis of government as social contract theorists pretend. There is nothing to transmit that original contract onwards from generation to generation, and our experience of actual political events shows that governmental authority is founded on conquest, not elections or consent. We do not even tacitly consent to a contract since many of us have no real choice about remaining in our countries: “Can we seriously say that a poor peasant or artisan has a free choice to leave his country, when he knows no foreign language or manners, and lives from day to day by the small wages which he acquires?” Political allegiance, he concludes, is ultimately based on a primary instinct of selfishness, and only through reflection will we see how we benefit from an orderly society.

Concerning private property, in both the Treatise and the Enquiry Concerning the Principles of Morals(1751), Hume in essence argues against Locke’s notion of the natural right to private

property. For Hume, we have no primary instinct to recognize private property, and all conceptions of justice regarding property are founded solely on how useful the convention of property is to us. We can see how property ownership is tied to usefulness when considering scenarios concerning the availability of necessities. When necessities are in overabundance, I can take what I want any time, and there is no usefulness in my claiming any property as my own. When the opposite happens and necessities are scarce, I do not acknowledge anyone’s claim to property and take what I want from others for my own survival. Thus, “the rules of equity or justice [regarding property] depend entirely on the particular state and condition in which men are placed, and owe their origin and existence to that utility, which results to the public from their strict and regular observance” (Enquiry Concerning the Principles of Morals, 3). Further, if we closely inspect human nature, we will never find a primary instinct that inclines us to acknowledge private property. It is nothing like the primary instinct of nest building in birds. While the sense of justice regarding private property is a firmly fixed habit, it is nevertheless its usefulness to society that gives it value.

As for Hume’s informal essays on popular political controversies, several of these involve party disputes between the politically conservative Tory party that supported a strong monarchy, and the politically liberal Whig party which supported a constitutional government. Two consistent themes emerge in these essays. First, in securing peace, a monarchy with strong authority is probably better than a pure republic. Hume sides with the Tories because of their traditional support of the monarchy. Except in extreme cases, he opposes the Lockean argument offered by Whigs that justifies overthrowing political authorities when those authorities fail to protect the rights of the people. Hume notes, though, that monarchies and republics each have their strong points. Monarchies encourage the arts, and republics encourage science and trade. Hume also appreciates the mixed form of government within Great Britain, which fosters liberty of the press. The second theme in Hume’s political essays is that revolutions and civil wars principally arise from zealousness within party factions. Political moderation, he argues, is the best antidote to potentially ruinous party conflict.

In economic theory, Hume wrote influential essays on money, interest, trade, credit, and taxes. Many of these target the mercantile system and its view that a country increases its wealth by increasing the quantity of gold and silver in that country. For mercantilists, three means were commonly employed to this end: (1) capture gold, silver and raw material from other countries through colonization; (2) discourage imports through tariffs and monopolies, which keeps acquired gold and silver within one’s country’s borders; and, (3) increase exports, which brings in money from outside countries. In Great Britain, mercantile policies were instituted through the Navigation Acts, which prohibited trade between British colonies and foreign countries. These protectionist laws ultimately led to the American Revolution. The most famous of Hume’s anti-mercantilist arguments is now called Hume’s gold-flow theory, and appears in his essays “Of Money” (1752) and “Of the Balance of Trade” (1752). Contrary to mercantilists who advocated locking up money in one’s home country, Hume argued that increased money in one country automatically disperses to other countries. Suppose, for example, that Great Britain receives an influx of new money. This new money will drive up prices of labor and domestic products in Great Britain. Products in foreign countries, then, will be cheaper than in Great Britain; Britain, then, will import these products, thereby sending new money to foreign countries. Hume compares this reshuffling of wealth to the level of fluids in interconnected chambers: if I add fluid to one chamber, then, under the weight of gravity, this will disperse to the others until the level is the same in all chambers. A similar phenomenon will occur if we lose money in our home country by purchasing imports from foreign countries. As the quantity of money decreases in our home country, this will drive down the prices of labor and domestic products. Our products, then, will be cheaper than foreign products, and we will gain money through exports. On the fluid analogy, by removing fluid from one chamber, more fluid is drawn in from surrounding chambers.

9. History and Philosophy

Although Hume is now remembered mainly as a philosopher, in his own day he had at least as much impact as a historian. His History of England appeared in four installments between 1754 and 1762

and covers the periods of British history from most ancient times through the seventeenth-century. To his 18th and 19th century readers, he was not just another historian, but a uniquely philosophical historian who had an ability to look into the minds of historical figures and uncover the motives behind their conduct. A political theme underlying the whole History is, once again, a conflict between Tory and Whig ideology. In the Britain of Hume’s day, a major point of contention between the two parties was whether the English government was historically an absolute or limited monarchy. Tories believed that it was traditionally absolute, with governmental authority being grounded in royal prerogative. Whigs, on the other hand, believed that it was traditionally limited, with the foundation of government resting in the individual liberty of the people, as expressed in the parliamentary voice of the commons. As a historian, Hume felt that he was politically moderate, tending to see both the strengths and weaknesses in opposing viewpoints:

With regard to politics and the character of princes and great men, I think I am very moderate. My views of things are more conformable to Whig principles; my representations of persons to Tory prejudices. Nothing can so much prove that men commonly regard more persons than things, as to find that I am commonly numbered among the Tories [Hume to John Clephane, 1756].

However, to radical Whig British readers, Hume was a conservative Tory who defended royal prerogative.

Hume takes two distinct positions on the prerogative issue. From a theoretical and idealistic perspective, he favored a mixed constitution, mediating between the authority of the monarch and that of the Parliament. Discussing this issue in his 1741 Essays, he holds that we should learn “the lesson of moderation in all our political controversies.” However, from the perspective of how British history actually unfolded, he emphasized royal prerogative. And, as a “philosophical historian,” he tried to show how human nature gave rise to the tendency towards royal prerogative. In his brief autobiography, “My Own Life,” he says that he rejected the “senseless clamour” of Whig ideology, and believed “It is ridiculous to consider the English constitution before that period [of the Stuart Monarchs] as a regular plan of liberty.” Gilbert Stuart best encapsulated Hume’s historical stance on the prerogative issue: “his history, from its beginning to its conclusion, is chiefly to be regarded as a plausible defence of prerogative” (A View of Society in Europe, 1778, 2.1.1). In short, Hume’s Tory narrative is this. As early as the Anglo Saxon period, the commons did not participate in the king’s advisory council. The Witenagemot, for example, was only a council of nobles and bishops, which the king could listen to or ignore as he saw fit. Throughout the succeeding centuries, England’s great kings were those who exercised absolute rule, and took advantage of prerogative courts such as the Star Chamber. Elizabeth—England’s most beloved monarch—was in fact a tyrant, and her reign was much like that of a Turkish sultan. Charles I—a largely virtuous man—tried to follow in her footsteps as a strong monarch. After a few minor lapses in judgment, and a few too many concessions to Catholics, Protestant zealots rose up against him, and he was ultimately executed. To avoid over-characterizing royal prerogative, Hume occasionally condemns arbitrary actions of monarchs and praises efforts for preserving liberty. Nevertheless, Whig critics like Gilbert Stuart argued that Hume’s emphasis was decisively in favor of prerogative.

There is an irony to Hume’s preference for prerogative over civil liberty. His philosophical writings were among the most controversial pieces of literature of the time, and would have been impossible to publish if Britain was not a friend to liberty. Although Hume was certainly no enemy to liberty, he believed that it was best achieved through moderation rather than Whig radicalism. He writes, “If any other rule than established practice be followed, factions and dissentions must multiply without end” (History, Appendix 3). To Hume’s way of thinking, the loudest voices favoring liberty were Calvinistic religious fanatics who accomplished little more than dissention. A strong, centralized and moderating force was the best way to avoid factious disruption from the start.