Responses To These Arguments

2.8.1. Dualism and Idealism

One way to respond to these arguments is to accept the conclusion and embrace dualism. We would thereby accept that physical science is not a complete description of the universe, and that the facts about consciousness are forever beyond the reach of science, or at least (see e.g. Chalmers, 1996) must be added to the physical facts as brute stipulations. These properties cannot be entailed by, or reduced to, or analysed in terms of, any physical property.

The chief problem with dualism has already been mentioned. This is the problem of interaction. Consciousness seems to be causally relevant to our behaviour, but if it is not physical, then it cannot be causally relevant. Chapter five is devoted to this issue, so I won’t discuss it here. I will just say that my conclusion there is that the problem of interaction provides a compelling set of arguments against dualism.

Another way to respond to these problems is to adopt idealism. We thus become deeply sceptical about the existence of physical things, of the external world beyond our senses generally. In a way, this is a form of eliminativism, but what we eliminate from our theories is not the mental but the physical. Thus the problem of interaction does not arise; there is nothing for the mental to interact with. Further, we avoid having to deny the existence of the mental, which as I noted above is deeply counter-intuitive.

The problem of course is that we are inclined to say that the external world does exist, and that we have good reason to believe that physics describes it pretty well, and that we therefore have reason to think that the postulates of physics exist. For the purposes of this thesis I will assume that idealism is false and that some form of external realism is true. So I am still faced with the challenge of reconciling physicalism with the existence of consciousness.

2.8.2. Eliminativism and Revisionism

Another way to respond to these anti-physicalist arguments is to deny that there are any conscious experiences. Specifically, it is to deny premise (1) of the zombie and inverted spectrum arguments. Adopting eliminativism does of course defend physicalism from the arguments above, for if there is no consciousness, there is nothing to be dualist about.

However, to deny the existence of consciousness is to deny the incredibly obvious. I am conscious; there is something it is like to be me. Whether we should trust the evidence of our sensory experiences is a fair question, but to ask whether we

have sensory experiences is a question so close to madness that only a philosopher could ask it. To answer ‘no’ would be to deny the most undeniable aspect of our existence. For the purposes of this thesis I will rule out eliminativism.

There is a milder variety of eliminativism that might better be called

revisionism. This is to acknowledge that there isn’t anything which exactly fits the description of consciousness, but there is something pretty close to this; close enough in fact to deserve to be called consciousness despite the discrepancies. If we pursue this strategy we can ‘revise’ our concept of consciousness so that we can derive the existence of it from the physical facts more easily. Then zombies and spectres cease to be conceivable.

The problem is that if we revise too much we will lose sight of the special nature of consciousness that motivated these problems in the first place. Chalmers (1996, p i 05) likens this strategy to defining world peace as “a ham sandwich”; world peace becomes much easier to achieve, but it is a less satisfying achievement. As much as possible, therefore, I want to avoid revisionism.17

2.8.3. A Priori Physicalism

To hold this position is to hold that there is an a priori entailment from the physical facts to the consciousness facts.18 This easily defeats the zombie and spectre

arguments because, armed with this entailment, we could derive the phenomenal facts and would cease to find zombies or spectres conceivable. Likewise, Mary could use the entailment to figure out what it will be like to see red.

The problem is, of course, that we need to be able to formulate the entailment. In chapter six I will attempt this with respect to the general problem, but in chapter seven I will argue that it cannot be done for the specific problem.

17 As an example, Churchland (1988) might be interpreted as advocating revisionism, depending on how much is left of the “folk” concept of consciousness after she is done with it. We might eliminate the concept from our theories on grounds that it does not pick out a natural kind, without thereby denying that each of the various things it picks out exist. See Goldman (1993) for a discussion. I think our theories must take phenomenal consciousness seriously as an explanandum.

There is another, less convincing way of defending physicalism by a priori means. This is to provide an a priori argument that, while it argues that duplicates

(purported zombies and spectres) must have phenomenal properties, nevertheless remains silent as to how these properties are related to physics. That is, we can show that the duplicates must have these properties without explaining how they come to have them. The way to do this is to exploit the appearance of phenomenal properties in the explanations of our physical behaviour. I will consider this in chapter five.

2.8.4. A Posteriori Physicalism

This position is similar to a priori physicalism except that it has given up on the goal of delivering an a priori psychophysical derivation. 19 Rather it accepts that there is going to have to be an a posteriori identity somewhere in the derivation. That is, we do some neuroscience, cognitive psychology and such like, find the physical correlate of consciousness, and then simply declare that this just is consciousness. So, for example, we might declare that to have firing C-fibres just is to have an experience of pain. Then anything with the former has the later, and so zombies and spectres cease to be conceivable. An alternative way to construe this approach is that zombies and spectres continue to be a priori conceivable, but the inference from conceivability to possibility is rejected, in these specific cases.

The problem with a posteriori physicalism is that we are taking a crucial step (the a posteriori identity) largely for granted. We would of course do the best

neuroscience first to decide what to put on the left hand side of the identity claim, but we are still bluntly stipulating the identity with consciousness. We can - and must - defend this move. That is, if you want to postulate an a posteriori identity, you must explain the a posteriority. Part of doing this is arguing that this move is necessary,

90 and explaining why it is so. Chapter seven will be devoted to these issues.

19 See eg. Levine, 1998, or Loar, 1999.

20 McGinn’s (1989) position o f ‘Mysterian Physicalism’ resists classification under the headings I give here. It might perhaps be taken as an extreme form o f a posteriori physicalism: he holds that physicalism is true, but that we will never understand how it is true, and should reconcile ourselves to this.

2.8.5. Combined Physicalism

This brings me to my own position, which is combined physicalism. I hold that we can provide an a priori answer to the general question, but should change to an a posteriori answer to the specific question. This is because we need a stronger answer for the specific problem than we do for the general. Thus I think that zombies are inconceivable, but that spectres are a priori conceivable but metaphysically impossible.21

This position is not immediately attractive, at least if you value simplicity. I resisted this conclusion for some time. But I have become convinced of it, and the

arguments of this thesis are presented to defend it.

Why do we need a stronger answer for the specific question than for the general? The answer to this deserves its own section.