David Chalmers on Mind and Consciousness Richard Brown Forthcoming in Andrew Bailey (ed) Philosophy of Mind: The Key Thinkers. Continuum Press David Chalmers is perhaps best known for his argument against physicalism in the philosophy of mind (Chalmers 1996). But this is not his only contribution. He is a highly systematic philosopher who has offered important theories and insights in many areas of philosophy. In what follows we will separate Chalmers’ views into two broad projects. On the one hand we will look at what we might call the negative project where he aims to show that physicalism about consciousness cannot work. On the other hand we will look at what we can call his positive project, which consists in giving a theoretical account of consciousness and mind that is consistent with his anti- physicalism. I. The Case against Physicalism Chalmers starts with his distinction between what he calls the easy and hard problems of consciousness. The easy problems of consciousness all involve those things that straightforwardly involve functioning. This includes such things as discriminating, categorizing and reacting to the environment, the integration of information, reporting on our mental states, accessing our own internal states, focusing attention, controlling behavior in a deliberate way, and discovering the neural basis of sleep and wakefulness (Chalmers 2010 p 4). The hard problem of consciousness involves explaining why it is that any of that stuff gives rise to consciousness. The sense of consciousness invoked in the hard problem is that of phenomenal consciousness or there being something that it is like for one to undergo various mental processes and instantiating various mental states. Thus the hard problem is that of explaining why it is that any of the functioning mentioned above feels the way it does from the inside. In particular it seems that any of the functioning could have occurred in the absence of any conscious experience whatsoever. So take, for instance, my seeing a red tomato while hearing someone say ‘that’s a tomato’. It is one thing to explain how it is that light reflected from the tomato affects my eye and how that produces activity in the brain, which results in various utterances and the grouping of that physical object with fire trucks and oxygenated blood. But none of that seems to explain what it is like for me to see red, or why there should be anything that it is like for me to see red in the first place. So too, it is one thing to explain how sound waves lead to certain kinds of brain activity but that doesn’t seem to explain how I consciously hear the words or understand their meaning. Why does any of that information processing happen consciously? Why isn’t it all done in the dark? One intuitive response at this point is to insist that at some point in the future we will be able to see how the hard problem is not really all that hard after all. Sometimes people use examples like life itself. It was once thought that we could not explain life in purely physical terms and that we would need to posit some mysterious non-physical essence to account for the difference between living and non-living things. We now think this isn’t true, and that we can give a physical account of what it means to be alive. So, too, perhaps, the same will be true for consciousness in 1,000 years. But this response is not promising according to Chalmers (2010 p. 16). In the case of life it does in fact seem that what needs explaining are functional ideas. What is so striking about consciousness, from his perspective, is that it is totally unique in that it seems to be something more than function. When one has a conscious experience of pain, or seeing blue, or listening to jazz, or thinking about the philosophy of mind, one is in various states that differ from each other in what it is like for one to have them. Explaining why this is the case doesn’t seem to be a matter of merely explaining functions. This is what makes the hard problem so hard. So far this is just a puzzle. Given that we know we have conscious experience how do we explain how it arises from structure and function? It is not yet an argument. But an argument immediately presents itself. Following Chalmers (Chalmers 2010 p 106) we can call this the explanatory argument. 1. Physical accounts explain at most structure and function 2. Explaining structure and function does not suffice to explain consciousness 3. No physical account can explain consciousness This argument captures the case against physicalism in its essence. It is intuitively plausible that if no physical account can explain consciousness then there is more in the world than what our physical sciences tell us. But the argument leaves much to be desired. One could insist that explaining structure and function is enough to explain consciousness, thereby denying that there is a hard problem of consciousness, or one could insist that failure to explain does not mean that there is more to our world than the physical. Chalmers argues that when one looks at the various a priori arguments against physicalism one can see a pattern emerge (2010 p107, 193–203). These arguments start from an epistemic or conceptual gap between consciousness and physical properties and move to there being an ontological gap. That is exactly what was going on in the above explanatory argument. An explanatory gap, as Joe Levine (1983) calls it, leads us to infer that there is more in the world that what is merely physical. To take another example, we can look at the Knowledge Argument advanced originally by Frank Jackson (1986). We imagine a super scientist who has been kept in a black and white room but who nonetheless has access to all of the physical theory about the world. Mary, as she is called, has never seen colors until one day she is released and sees a red ripe apple. She says ‘ah! that’s what it is like for one to see red!’ Given that Mary cannot know what it is like to see red in her black and white room (that is, that there is an epistemic gap), but yet she knows all of the facts that can be captured by structure and function, the argument concludes that knowing what it is like to see red is knowing something beyond the physical facts. We cannot deduce one from the other. Or, finally, take Kripke’s (1980) well-known modal argument. In its basic form the modal argument goes as follows. Identity statements are necessarily true, if true at all. Those who think otherwise, like the early identity theorists (see chapter 6) are actually confused. When we think we can imagine lightning, say, without electrical discharge, what we really imagine is something that superficially presents the same appearance as electrical discharge (i.e. lightning) does to us, but which is not lightning. It is essentially fool’s lightning, or something which resembles our lightning but is not. So if mind/brain identity statements were true then it would be impossible to have one without the other. But in the case of, say, ‘pain is identical to some neural activity’ it seems easy to imagine the pain without the neural activity and the neural activity without the pain. But if so then how can we explain the fact that the identity is necessary? It seems we cannot appeal to the previous strategy since it doesn’t seem to make sense to say that there is something that presents itself in the same way that our pain does but is not really pain. Though the arguments against physicalism all have a similar structure the one that is most well worked out, and which makes all of the issues maximally clear, is the two-dimensional conceivability argument (2010 p 142), which has the following form: 1. P&~Q is conceivable 2. If P&~Q is conceivable then it is metaphysically possible 3. If P&~Q is metaphysically possible then physicalism is false The ‘P’ above is a placeholder that can be filled in with whatever physical theory you like. It is meant to be a total description of the world in physical terms. The ‘Q’ is a claim about phenomenal consciousness, like that I see blue or that someone feels pain. Each premise needs to be clarified and defended. Premise one says that we can conceive of all of the physical facts holding without any consciousness at all. This is what Chalmers calls a zombie world. This premise relies on what Chalmers calls ideal negative conceivability. The notion of ideal conceivability is meant to capture what an ideal reasoner would be able to conceive under ideal conditions as opposed to what merely seems conceivable under certain impoverished reasoning conditions to a less than ideal reasoner. Something is negatively conceivable just when it cannot be ruled out on a priori grounds. Something is positively conceivable when we are able to form some positive conception of the thing in question. It goes beyond merely not noticing any contradictions. In addition we are able to form some conception of how the thing in question could be true. Given this premise one says that it is ideally negatively conceivable that there be a zombie world. This in turn means that this world is not ruled out a priori or that there is nothing contradictory that follows from this description of the world.