Chalmers begins by setting out again the Hard Problem (a term with which his name will forever be associated) of explaining phenomenal experience – why is it that ‘there is something it is like’ to experience colours, sound, anything? The key point is that experience is simply not amenable to the kind of reductive explanation which science has applied elsewhere; we’re not dealing with functions or capacities, so reduction can gain no traction. Chalmers notes – justly, I’m afraid – that many accounts which offer to explain the problem actually go on to consider one or other of the simpler problems instead.The zombie analogy is meant to show that it's perfectly possible that there could be beings exactly like us, but which are essentially blood and bone machines run by a brain that's an organic computer. Machines and computers don't experience sensations like color, flavor, etc., and since we do experience such things there must something more to us than just our material or physical hardware. There's something about us, the argument goes, that's immaterial and non-physical that's necessary to generate the phenomena of sensation, or what philosophers call qualia.
He now gives us a fuller account of the arguments in favour of qualia, the items of phenomenal experience, being a real problem for materialism, and categorises the positions typically taken (other views are of course possible).
In the other camp we have non-materialist views:
- Type A Materialism denies the epistemic gap: all this stuff about phenomenal experience is so much nonsense.
- Type B Materialism accepts the epistemic gap, but thinks it can be dealt with within a materialist framework.
- Type C Materialism sees the epistemic gap as a grave problem, but holds that in the limit, when we understand things better, we’ll understand how it can be reconciled with materialism.
Finally we have the option that Chalmers appears to prefer:
- Type D dualism puts phenomenal experience outside the physical world, but gives it the power to influence material things,
- Type E Dualism, epiphenomenalism, also puts phenomenal experience outside the physical world, but denies that it can affect material things: it is a kind of passenger.
Chalmers concentrates on the conceivability argument: this is basically the point often dramatised with zombies, namely that we can conceive of a world, or people, identical to the ones we’re used to in all physical respects but completely without phenomenal experience. This shows that there is something over and above the physical account, so materialism is false.
- Type F monism (not labelled as a materialism, you notice, though arguably it is). This is the view that consciousness is constituted by the intrinsic properties of physical entities: Chalmers suggests it might be called Russellian monism.
The problem of consciousness is one of the most important of the contemporary philosophical debates because it bears on the view we hold of the nature of human beings: Are we just material entities or are we some sort of composite of matter and mind (or soul)? If consciousness can ultimately be explained purely in terms of chemical reactions in the brain then materialism is probably true. If consciousness requires something more than matter to explain its character then materialism is probably false.
The book is not for beginners, and anyone who thinks they might be interested in the topics it addresses is advised to first read the review at Conscious Entities.