The Mind/Body Problem

Transcription

1 The Mind/Body Problem This book briefly explains the problem of explaining consciousness and three proposals for how to do it. Site: HCC Eagle Online Course: 6143-PHIL-1301-Introduction to Philosophy-S8B Book: The Mind/Body Problem Printed by: Nathan Smith Date: Saturday, 31 May 2014, 6:51 PM 1 of 9 5/31/14, 6:52 PM

2 Table of contents The Hard Problem Cartesian Dualism Identity Theory The Principle of Parsimony Multiple Realizability Type and Token Identity Functionalism 2 of 9 5/31/14, 6:52 PM

3 The Hard Problem One of the hardest problems in philosophy is the question of how physical processes in the brain give rise to subjective experience. Indeed, David Chalmers calls this "The Hard Problem". The problem has been with us for a long time; it is a variation of what is also known as the mind/body problem: what is the relation between mental states (which are essentially private) and physical states (which are, in principle, public)? 3 of 9 5/31/14, 6:52 PM

4 Cartesian Dualism Descartes' answer is that there are two kinds of substances, immaterial substance (mind) and material substance (body), and the two kinds of substances causally interact. When, for example, you drop a bowling ball on your foot, the nerves at the surface of your foot are excited, which sends an electrical signal up your spine and to your brain, which is precisely the point, according to Descartes, where all this material activity causes the immaterial stuff of your mind to feel pain. It s the felt quality of this experience (i.e., consciousness) that then causes you to hop around on one leg and reach for a bottle of ibuprofen. This view is known as Cartesian (or Substance) Dualism. Dualism accounts for the essential privacy of mental states by positing a special kind of substance. Descartes attempts to prove the existence of this immaterial substance by invoking Leibniz Law, which says that if two names pick out the very same thing (x=y), then all and only what is true of x is also true of y. It follows from Leibniz Law that if something is true of mental states that is not true of physical states, or vise versa, then mental states are not physical. If brain states, for example, take up space and are located in a particular place, and the belief that I need medical attention lacks these properties, then a belief is not a physical thing. 4 of 9 5/31/14, 6:52 PM

5 Identity Theory In spite of these apparent proofs, dualism is not without its detractors. For one thing, it s hard to see how one would defend the view that a belief is not located unless one already accepts dualism, which would mean that this sort of argument begs the question. So, guided by the conviction that all phenomena including consciousness are amenable to scientific explanation, philosophers like David Lewis and JCC Smart began articulating philosophical arguments for what we might call Identity Theory : there is only one kind of substance, it s material (this part is called "Materialism"), so conscious mental states are identical with physical states of the brain. Just as we came to discover that water is H 2 O, and lightning is a kind of electrical discharge, we will come to discover that the type of brain activity correlating with the felt experience of pain, just is the pain. There is no causal interaction between the brain state and the mental state. The mental state is the brain state, end of story. How might we come to discover that a conscious mental state like pain just is a kind of neurophysiological brain state? You might think we could do tests to determine this. Put a subject into an fmri machine and poke needles into his foot and look for brain activity. But notice that such tests will always be consistent with the view that what is being imaged is causing the feeling in the subject, in which case the feeling and the brain activity are not identical. In fact, no strictly empirical test can prove that Identity Theory is correct, or incorrect for that matter. 5 of 9 5/31/14, 6:52 PM

6 The Principle of Parsimony So why should we believe Identity Theory? The philosophical argument for Identity rests on another important principle: The Principle of Parsimony (also known as Ockham s Razor). The principle of parsimony says that when two theories are each explanatorily adequate (they each explain the phenomena in question), we ought to choose the simpler theory. How do we decide which theory is simpler? This is a difficult question, but, intuitively, if theory X relies on extra entities, processes, or mechanisms, to explain the same phenomena that theory Y explains, then Y is simpler. The Identity theorist claims that Identity is simpler than Dualism, since Identity explains conscious mental states with just one kind of stuff and thus doesn t have to posit some sort of mysterious causal connection between material and immaterial stuff. 6 of 9 5/31/14, 6:52 PM

7 Multiple Realizability One issue for the above argument is that, while the principle of parsimony might be a useful methodological principle, we cannot be sure that the simpler theory is always the correct theory. There may be phenomena that do indeed involve additional mechanisms and/or entities and we should not rule out this possibility a priori. A different criticism is that Identity is not empirically adequate, for it cannot account for the essential privacy (the quality of) of mental states. Yet another sort of criticism comes from within the materialist camp: David Lewis himself seems to deal a crushing blow to Identity Theory with his 1978 paper, Mad Pain and Martian Pain, in which he argues that pain and other mental states may very well be realized in creatures very dissimilar to us (e.g., extraterrestrials), and even manifest itself differently in the behavior of different human beings (e.g., people for whom pain causes giggling). To accommodate the multiple realizability of mental states, Lewis suggests that we identify them not with kinds of physical states, but with kinds of causal states that are fixed for a population, but contingent. 7 of 9 5/31/14, 6:52 PM

8 Type and Token Identity Lewis' idea is to preserve the insight that consciousness must be amenable to scientific investigation, and so be (identical with) physical states in every sort of thing that experiences conscious mental states like pain; but reject the problematic idea that everything that experiences pain and other mental states must be just like us. The former insight is known as Token Identity; whereas the latter, more problematic notion is known as Type Identity. Multiple realizability is only a problem for Type Identity. In humans, Lewis suggests, pain might be a kind of neurological state. Thus, the madman in just this state, because he is human, is in pain even though his is caused by different stimuli and issues in unique behavior. But in Martians, because the physical process by which pain occurs is contingent, pain might be the inflation that occurs in cavities in his feet, which causes him to do what we do when we experience injury: recoil. 8 of 9 5/31/14, 6:52 PM

9 Functionalism This theory is known as Functionalism. As Lewis puts it, the concept of pain, or indeed any of any other experience or mental state, is a [physical] state apt for being caused in certain ways by stimuli plus other mental states and apt for combining with certain other mental states to jointly cause certain behavior. So for example, when a bowling ball falls on your foot (stimuli), your pain is whatever physical state members of your species would normally be in which causes most of us to hop up and down on one foot and reach for a bottle of ibuprofen (behavior). When a Martian is subject to roughly the same stimuli (of course, their world may be devoid of bowling balls), his pain is whatever physical state he is in that causes roughly the same kind of behavior in typical Martians. An interesting consequence of functionalism is that it provides an opening for the possibility of artificial consciousness. For if Lewis Martians can experience pain in virtue of their hydraulic plumbing, then perhaps a machine might be made that experiences pain in virtue of its ability to respond appropriately to external stimuli. The interesting philosophical question is: what would the machine have to be like to convince us that it is actually experiencing pain, and not just acting like it is? 9 of 9 5/31/14, 6:52 PM