In this paper I will examine and criticize the arguments David Chalmers gives for rejecting a materialistic account of consciousness in his book The Conscious Mind. I will draw upon arguments and intuitions from the three main schools of thought in the philosophical study of consciousness(a) forms of dualism, (b) materialism, and (c) eliminativism. Chalmers’ book deals with what are currently the most controversial issues in the study of consciousness, especially among these three schools of thought, so it provides a good guide to the important issues.
This paper will concentrate on the debate between dualist and materialist theories of consciousness. I will draw on the views of Joseph Levine and discussions with Ken Taylor for materialist theories, on Chalmers’ book for a dualist perspective, and I will use Dennett’s writings for eliminativist considerations. In his book, Chalmers argues that if one is to “take consciousness seriously,” one should endorse a dualistic theory like his property dualism because materialism cannot explain how consciousness could amount to physical structures and processes.
In the process, Chalmers argues against the eliminativist position which he claims does not “take consciousness seriously. ” I will begin by explaining the important concepts in the dualist-materialist-eliminativist debate such as consciousness; logical, metaphysical, and natural supervenience; and zombies. Next, I will explicate what I take to be Chalmers’ main argument for property dualism. I will then explain where a materialist could object to Chalmers’ argument, and how Chalmers tries to rule out such a response.
Finally, I will conclude with considerations of the fundamental intuitions and assumptions each of the three views of consciousness leads to, and I will ultimately argue that of all three views, materialism is the best theory. First, what is consciousness? Consciousness is often referred to by philosophers as what it’s like to feel pain or to see the color red. Qualia, phenomenal feel, and the subjective quality of experience are terms used by philosophers which all make reference to consciousness.
The basic idea is that when one has an experience, a pain in the foot for example, it seems theoretically possible to separate all of the neuron firings, information processing in the brain, and behavioral responses, from what will be leftthe feeling of pain (this is also called the phenomenal feel or the qualia associated with pain). Dualists disagree with both materialists and eliminativists on whether it is possible to separate consciousness from all the nerve impulses, information processing, etc. , which occur in a conscious person’s brain.
Eliminativists such as Dennett claim that there isn’t any phenomenon above and beyond all such brain processes and their interaction left to explain. Performing imaginative thought experiments might make us think that there is something other than the things going on in our bodies (some experience), but we are mistaken. This fundamental difference of intuitions immediately separates eliminativist theories from theories like Chalmers’, and to a lesser extent from the sort of theory most materialists would defend.
We are left with the question of how best to explain (or explain away) “consciousness”; this question is what I refer to throughout this paper as the problem of consciousness. One way in which the problem of consciousness can be viewed is to think of it as the old mind-body problem with a new set of concepts to consider. One of the most important of these in recent debate about consciousness is that of supervenience. Supervenience can be understood on many levels. Basically, it describes a dependence relation between two sets of properties.
A set of higher level properties supervenes on a set of lower level properties if the higher level properties depend upon the lower level properties. Chalmers defines supervenience as “B-properties supervene on A-properties if no two possible situations are identical with respect to their A-properties while differing in their B-properties” (Chalmers 33). The notion of supervenience is meant to capture our belief that in processes such as life, higher level properties of organisms (e. g. , size, shape, and behavior) really depend upon and can be explained by much lower level properties (such as genes, DNA, nerve impulses, etc.
This rather simple notion of supervenience can be divided into many highly technical sub-categories, each with slightly different interpretations and meanings. For the purposes of this paper, a grasp of the differences between logical, metaphysical, and natural supervenience will be sufficient to understand the arguments put forth by materialists, property dualists, and eliminativists. Logical supervenience can be characterized by the claim: B-properties supervene logically on A-properties if it is logically impossible for two situations to have exactly the same B-properties without also sharing the same A-properties.
Another way of thinking about this is to consider what it would be in God’s power to create. It would be impossible for God to create a world in which, for example, bachelors were married. Due to the meanings of those two terms, it is logically impossible for a bachelor to be married. Therefore, bachelorhood logically supervenes on a man’s marital status. However, it does seem possible that God could have made a world in which the ideal gas laws did not hold. (1) This certainly could not happen in our world, but if God were to change a few of the laws of physics, the ideal gas law could also change.
This brings us to the notion of natural (or nomic) supervenience. Chalmers describes natural supervenience as the result of two sets of properties being “systematically and perfectly correlated in the natural world” (Chalmers 36). Formally, the concept of natural supervenience is: B-properties supervene naturally on A-properties if any time two situations which could naturally arise in our world share the same A-properties, they also share the same B-properties. Whether some property naturally supervenes on another property depends upon our world and the natural laws (i. e. he laws of physics) in our world. Natural supervenience has to do with empirical possibilitysituations which a
re causally necessitated in our world (though not in all possible worlds). The example of the ideal gas laws is an example of a naturally necessary phenomena which is not logically necessary (it’s conceivable, at least, that it could be different). If B-properties naturally supervene on A-properties, then while it is conceivable that the same B-properties could be instantiated without the same A-properties, it could never happen in our world because it would break the laws of physics.
Finally, the notion of metaphysical supervenience is based upon rather subtle distinctions between a priori and a posteriori identities of substances. Metaphysical supervenience stems from the notion of metaphysical identity, which Saul Kripke is credited with discovering. In his book Naming and Necessity, Kripke distinguishes between two subtly different notions of identity. Logical identity is just the same as has been explained earliertwo things are said to be logically identical if, because of the meanings of the terms, it is impossible that they could be distinct things.
Metaphysical identity, on the other hand, depends upon how our world turns out. The classic example of metaphysical identity is the identity of water and H2O. Kripke argues that although it is imaginable that the stuff we find in lakes and oceans, which is good to drink, and which we call ‘water’, might not have had the chemical composition H2O, once we discover that it does have this chemical composition in our world, H2O will be ‘water’ in all possible worlds (even those which have a substance with a different chemical composition in the lakes and oceans).
Therefore, even though it is imaginable that water is not H2O, one can discover the identity of water and H2O a posteriori, and this identity is as valid an identity as those which can be known a priori. So, water is metaphysically identical to H2O. The fact that the metaphysical identity of water and H2O is a posteriori explains the apparent contingency of the statement “water is H2O” because, had the world been different, that statement might have been false.
Getting back to supervenience, the formal definition of metaphysical supervenience is: B-properties supervene metaphysically on A-properties if it is metaphysically impossible for two situations/objects to have exactly the same B-properties without having the same A-properties. For example, properties of physical objects in our universe metaphysically supervene on properties of atoms (or whatever the true fundamental particles are) because it is metaphysically impossible for two physical objects to have the same properties without the same properties of their respective atoms being instantiated.
This is different from logical supervenience because it is imaginable that physical objects might not have been made up of atoms, in which case the properties of atoms would make no difference to the properties of physical objects. However, because we have empirically discovered that objects in our world are made up of atoms, then in all possible worlds the properties of those things which classify as physical objects will depend on the properties of atoms. Having established that framework, we can now move on to discuss Chalmers’ arguments.
In the recent debate over the problem of consciousness, materialists often appeal to some form of metaphysical identity or metaphysical supervenience as a way of holding on to materialism while still admitting that the problems Chalmers points out are real. Chalmers disagrees that the notion of metaphysical identity can save materialism, and he spends much of Chapter 2 and the entire section Objections from a posteriori necessity in Chapter 4 arguing against such a materialist approach.
Before Chalmers begins to develop his own dualistic theory, he argues that materialism must hold that consciousness is logically supervenient on the physical; that materialists cannot appeal to metaphysical supervenience as a way of avoiding the problems he raises with logical supervenience; and that therefore, materialism fails. In this paper, I will first discuss Chalmers’ arguments against the logical supervenience of consciousness before turning to his arguments against the metaphysical supervenience of consciousness which I believe to be wrong.
In The Conscious Mind, Chalmers’ first argument against the logical supervenience of consciousness stems from the logical possibility of “zombies. ” A zombie, in the philosophical literature, is supposed to be a being just like a person in all respects (behavior, language ability, appearance, possession of beliefs and desires) except that it lacks all consciousness. (2) Chalmers imagines his zombie twin, a being physically identical to him who lives on a twin Earth that has an environment physically identical to ours.
Chalmers’ zombie twin looks and acts just like the real Chalmers does in our world, but he does not have any of the phenomenal experiences that the real David Chalmers has. This imaginative exercise is meant to show that zombies are logically possible creatures, and Chalmers argues that the logical possibility of zombies proves that materialism is false. His argument can be summarized as the following premises: (1) Consciousness exists in our world; this is an empirical claim. (2) Because zombies are logically possible, consciousness cannot logically supervene on the physical.
If consciousness does not logically supervene on the physical, then one cannot reduce facts about consciousness to physical facts; therefore, one cannot explain the occurrence of consciousness just by appeal to the physical facts. Chalmers contends that materialism is committed to the view that consciousness is logically supervenient on the physical, in which case materialism is false. Although Chalmers provides other arguments for the falsity of materialism, this is his strongest, and it will be worth examining the premises and intuitions behind this argument.