Philosophy 101 Day 13

1. Philosophy 101 Day 13 Copyright 2006 Makoto Suzuki

2. Aims • Introduce materialism and substance dualism. • Consider the potential problems of distinguishing the soul from the mind. • Mention the relationship between the mind-body problem and the problem of afterlife. • Examine three of Mary’s reasons for materialism. • Examine Dave’s two arguments for substance dualism.

3. Characters in Mind and Brain, and Their Positions • Mary Materialists • Materialism: the mind is a physical substance; and all mental processes, events and states are identical with physical processes, events and states. (p.2) • Caution: in the mind-body debate, a biological substance like a brain counts as physical. • Dave (Substance) Dualists • Substance Dualism: the mind is a nonphysical substance; and mental processes, events and states are not identical with physical processes, events and states. (p.3) • Steve Skeptical of both positions

4. Mind and Soul (p.2) • While many identify the soul with the mind, others don’t. • It is fair to ask those who believe that the soul is distinct from the mind the following questions: • What is the distinction between the soul and the mind? What is soul anyway? • Given that soul is distinct from the mind, can we know whether someone has the soul? How? • Given that soul is distinct from the mind, is there any reason to believe that some beings – human beings (only?) – have soul but others – rocks, plants, non-human animals etc. – don’t?

5. Materialism, Substance Dualism and the Requirement of Life after Bodily Death (p.3) • If materialism is true, life after bodily death requires the duplication and revitalization of body. • Dave claims that if substance dualism is true, it can continue to exist without our body and therefore survive bodily death. • In the next class session we will consider whether David’s claim is true.

6. Three of Mary’s Reasons for Materialism • An Evolutionary Consideration (pp.4-5) • A Scientific Consideration (p.5) • Simplicity • Mary and Steve think there are other reasons for favor materialism, but we will see them in the next class session.

7. Three of Mary’s Reasons for Materialism:1. An Evolutionary Consideration (pp.4-5) • Substance dualism makes it hard to explain how the organisms with the mind have evolved through natural processes from the organisms without the mind. • According to substance dualism, the mind is a nonphysical substance. How can a nonphysical thing come to existence through natural processes from a different – physical – kind of things? • Materialism has less difficulty here. • According to materialism, the mind is a physical substance. There is no problem of explaining how a nonphysical thing can come to existence from natural processes from a physical thing.

8. Three of Mary’s Reasons for Materialism: 2. A Scientific Consideration (p.5) • Mary argues as follows. • “If materialism is true, it is at least possible to explain mental functioning in terms of the brain. On the other hand, if dualism is true, then it would be impossible to observe or to scientifically examine the mind. You must admit that in this sense materialism has a general advantage.” • This passage is perplexing. Even if materialism makes scientific investigation into the mind possible, why does this fact make materialism more plausible?

9. One Interpretation • One interpretation of Mary’s argument is as follows. • We think that scientific investigation into the mind is possible. • If materialism is true, then scientific investigation into the mind is possible. If substance dualism is true, however, it is impossible. • Therefore, materialism, not substance dualism, is consistent with our view that scientific investigation into the mind is possible. • Thus, we have a reason to believe materialism rather than substance dualism.

10. Possible Replies • You might object to the claim that if substance dualism is true, scientific investigation into the mind is impossible. • However, if scientific investigation into the mind is possible, doesn’t it imply that the mind is physical (as opposed to nonphysical)? • You might object to the claim that we believe that scientific investigation into the mind is possible. • You then need to deny either (1) that psychology, neuroscience etc. can shed light on the nature of the mind, or (2) that these are scientific investigations.

11. Three of Mary’s Reasons for Materialism: 3. Simplicity (p.5) • The principle of simplicity says that we have a reason to favor the theory that posits fewer objects or the one that is more simple. • While substance dualism posits two kinds of things – physical and nonphysical – , materialism posits only one kind of things. • Therefore, according to the principle of simplicity, we have a reason to favor materialism over substance dualism.

12. Why Accept the Principle of Simplicity? • Consider the following two theories: • (1) an object will stay at rest or move at a constant speed in a straight line unless acted upon by an unbalanced force; and, • (2) spirits will make an object stay at rest or move at a constant speed in a straight line unless acted upon by an unbalanced force. • We will favor (1) over (2) because (2) posits something superfluous to explanation, i.e., spirits. • The Principle of Simplicity spells out this intuitive way of reasoning.

13. Possible Replies • Argue against the principle of simplicity, or argue that it does not apply to the mind-body debate. • Accept that materialism is simpler, but argue that it has problems in other respects. • David points out, for example, that it appears mysterious how the brain – the wet, slimy, grey and white stuff in the skull – can be the mind, or how neurological processes can be thoughts, pains, fears, loves, etc. (p.6) • Materialists typically respond that once we understand the mechanism of the brain, this appearance of mystery disappears; as life turns out to be the complex workings of a complex mechanism, mentality will also turn out to be the complex workings of a certain complex mechanism.

14. Dave’s Two Arguments for Substance Dualism • The Divisibility Argument (pp.8-14) • The Argument from Introspection (pp.14-19) • Because both arguments use Leibniz’s Law, we will consider this principle first.

15. Leibniz’s Law (p.8) • Leibniz’s law is a principle about identity. • It says that for any x and y,if x is identical with a thing y, then x and y have all of the same properties. • Here a thing can be an event, object, process or whatever. • This principle implies that for any x and y, if x and y do not share some property, then x is not identical with y. Gottfried Wilhelm Leibniz (1646-1716)

16. Libnitz’s Law Applies to Normal Contexts. • Libnitz’s Law Applies to normal contexts. Examples: • Babe Ruth played most of his career for the Yankees. • The first player to hit 60 home runs in a season played most of his career for the Yankees. • 1 is true if and only if 2, which replaces “Babe Ruth” with “the first player to hit 60 home runs in a season” (which refers to the same person), is true. Actually, both are true. • Karen’s pool is filled with water. • Karen’s pool is filled with H2O. • 1 is true if and only if 2, which replaces “water” with “H2O”, is true.

17. 1. Divisibility Argument (pp.8-14) • Everyone’s body, which includes his or her brain, is divisible. • I cannot conceive, through introspection, of my mind as divided. • (From 2) It is impossible to conceive of anybody’s mind as divided. • (From 3) Nobody’s mind can be divided. • (From 1 and 4) Everyone’s body has the property of divisibility, but his or her mind lacks divisibility. • Leibniz’s Law is true. • (From 6) For any x and y, if x and y do not share some property, then x is not identical with y. C Therefore, Everyone’s mind is distinct from any part of his or her body.

18. Criticisms • Equivocation • Some actually thinks, through introspection, that the mind has parts. • Hasty generalization • Introspection is not the only test of conceivability.

19. 1. The Problem of the Premise 2 and 3: Equivocation (pp.10-11) • In the argument, “conceive” is perhaps used ambiguously. • “Conceive” something can mean (1) imagining it – forming an mental imagery or picture of it –, or (2) understanding it – making sense of it. • (2) does not require (1). For example, we cannot form a mental picture of a 10,000-sided polyhedron, but we can make sense of it. • On the one hand, even if we cannot have a mental picture of the divided mind, it does not show that it cannot be divided. • Analogy: A 10,000-sided polyhedron is surely possible.

20. Continued • On the other hand, if we cannot make sense of the idea that the mind is divided because the idea is incoherent, then we can legitimately infer that the mind is not divisible. • Analogy: we cannot make sense of round square, and it is impossible. • However, it seems that we can make sense of the idea that the mind is divided, i.e., has parts. There seems to be no incoherence in this idea.

21. Summary • On the one hand, if we take “conceive” to mean “imagine”, then we cannot infer from the inconceivability of the divided mind that the mind cannot be divided. • On the other hand, if we take “conceive” to mean “understand”, it seems false that we cannot conceive of the divided mind. • If we thought that the divisibility argument shows that the mind cannot be divided, it is merely because we mixed two meanings of “conceive” together.

22. 2. The Problem of the Premise 2: Introspecting Parts of the Mind (pp.9-10) • Mary argues that when she introspects her mind, she thinks of her mind as divided – as having parts, such as memories, beliefs, fears, desires and so on. • A possible reply is that she confuses the meaning of parts with the meaning of aspects. • The blackness and disheveledness of my hairs is not part of my hairs but rather their aspects. In the same way, memories, beliefs, fears, desires and so on are not parts of the mind, but rather the aspects of the part-less mind. • However, it is not clear whether Mary or any other person makes such confusion in thinking through introspection that the mind is composed of parts.

23. The Problems of Arguing from 2 to 4. • Hasty Generalization (p.13) • The argument generalizes from one case, ‘my’ mind, to all cases, everyone’s mind. • Introspection not the only test of conceivability • Even if I cannot conceive, through introspection, of my own mind as divided, this does not mean that nobody can conceive of my own mind as divisible. • Multiple personality disorder suggests that even if one does not think of his mind as divided – having parts –, another person can. (pp.13-4) • The talk of unconscious/subconsciousness or of amnesia also suggests that even if one does not think his mind as divisible, another person can think of his mind as divided between the self-aware part and the hidden part. (p.14)

24. Argument from Introspection (pp.14-19) • Every mental state can be recognized merely through introspection. (OK?) • No brain state can be recognized merely through introspection. • (From 1 and 2) Every mental state has the property of being recognizable merely through introspection, but no brain state has that property. • Leibniz’s Law is true. • (from 4) For any x and y, if x and y do not share some property, then x is not identical with y. C (from 3 and 5) No mental states are brain states.

25. The Problem of Premise 4: Strictly Speaking, Leibniz’s Law is not true • Leibniz’s Law fails in intensional contexts, i.e., cases where replacing one co-referring expressions with another can change a statement’s truth-value. • Co-referring expressions are pairs of expressions that that refer to the same thing: for example, “Venus” and “the Morning Star”; “Babe Ruth” and “the first baseball player to hit 60 home runs in a season”; “Water” and “H2O”. • Leibniz’ Law says that the same properties are always attributable to these co-referring expressions (because they refer to the same objects). • However, strictly speaking, this is false.

26. Intensional Contexts: Examples (pp.16-19) • One type of intensional contexts involve sentences with mental expressions like “believe”, “conceive”, “think”, “know”, “recognize” etc. • Jane believes that Babe Ruth played most of his career for the Yankees. • Jane believes that the first player to hit 60 home runs in a season played most of his career for the Yankees. • If Jane is a normal American, 1 is true but 2 is false. • Karen recognizes that her pool is filled with water. • Karen recognizes that her pool is filled with H2O. • If Karen is a small kid, 1 is true but 2 is false.

27. The Failure of the Leibniz’ Law: An Example • Water can be recognized merely through observation. • H2O can be recognized merely through observation. • Apparently, 1 is true, but 2 is false. • From this we can infer that water is recognizable merely through observation but H2O is not. Applying Leibniz’s Law, we reach the conclusion that water is not identical with H2O. However, this conclusion is absurd. • In this way, in intensional contexts, Leibniz’s Law fails.

28. Argument from Introspection Applies Leibniz’s Law to an Intensional Context • Argument from Introspection starts from the two premises: • Every mental state can be recognized merely through introspection. • No brain state can be recognized merely through introspection. From this, the argument contends that every mental state has the property of being recognizable merely through introspection, but no brain state has that property. Applying Leibniz’s Law, we reach the conclusion that no mental state is a brain state. • This is an application of Leibniz’s Law to intensional contexts, so the conclusion fails to follow.