I've been studying Jaegwon Kim's Physicalism, or Something Near Enough (Princeton UP, 2005). Here are some notes and questions.
1. It's clear that mental causation must be saved. If Kim is right that nonreductive physicalism is not viable, then by his lights our only hope of saving mental causation is via "physical reductionism." (159). It is of course easy to see how such reductionism, if true, would save mental causation. Surely my desire for a beer together with my belief that there is beer in the reefer are part of the etiology of my getting out of my chair and heading to the kitchen. If beliefs and desires are physical states, then there is no in-principle difficulty in understanding the etiology of my behavior. Reductionism insures the physical efficacy of the mental. What was a thorny problem on dualist approaches is no problem at all for the physical reductionist.
2. At this point some of us are going to wonder whether reductionism collapses into eliminativism. I tend to think that it does. Kim of course must disagree. His project is to find safe passage between nonreductive physicalism and eliminativism. But first I want to concede something to Kim.
3. Kim rightly points out (160) that we cannot assume that the mental cannot be physical in virtue of the very meaning of 'mental.' We cannot assume that 'mental' means 'nonphysical.' The following argument is not compelling and begs the question against the physicalist:
Beliefs and desires are mental
Whatever is mental is nonphysical
Ergo
Beliefs and desires are not physical.
The physicalist finds nothing incoherent in the notion that what is mental could also be physical. So he will either reject the second premise, or, if he accepts it, deny the first and maintain that beliefs and desires are not mental in the sense in which his opponents think they are. It seems clear, then, that one cannot mount a merely semantic argument against the physicalist based on a preconceived meaning of 'mental.'
4. Is my present state of consciousness real and yet reducible to a pattern of electrical activity in a network of neurons? Can we secure reduction without elimination? Reductionist: there are Fs but what they are are Gs. Eliminativist: There are no Fs. There at least appears to be a difference in these two sorts of claims. Kim claims that "There is an honest difference between elimination and conservative reduction." (160) Phlogiston got eliminated; temperature and heat got reduced. Witches got eliminated; the gene got reduced. The reductionist thinks he can secure or "conserve" the reality of the Fs while reducing them to the Gs. In the present case, the physical reductionist in the philosophy of mind thinks that he can maintain both that mental states are real and that they reduce to physical states.
5. Let's note two obvious logical points. The first is that identity is a symmetrical relation. The second is that reduction is asymmetrical. Thus,
I. Necessarily, for any x, y, if x = y, then y = x.
R. Necessarily, for any x, y, if x reduces to y, then it is not the case that y reduces to x.
It is clear, then, that identity and reduction are not the same relation. And yet if particular a reduces to particular b, then a is nothing other than b, and is therefore identical to b. If you think about it, reduction is a strange and perhaps incoherent notion. For if a reduces to b, a is identical to b, but, since reduction is asymmetrical, b is not identical to a! Reduction is asymmetrical identity. Amd that smacks of radical incoherence. This is what inclines me to say that reduction collapses into elimination. For if a reduces to b, and is therefore identical to b, while b is not identical to a, then it follows that there simply is no a. And so if my present mental state reduces to a pattern of electrical activity in a network of neurons, then my mental state does not exist; all that exists is the electrical activity.
6. Kim wants to have it both ways at once. He wants mental states to be both real and reducible. He wants to avoid both eliminativism and dualism. My claim is that it is impossible to have it both ways. Kim thinks that reduction somehow "conserves" that which is reduced. But how could it? If my desire for a beer is nothing other than a brain state, then then it is a purely physical state and everything mental about it has vanished. If 'two' things are identical, then there is only one thing, and if you insist that that one thing is physical, then it cannot also be mental.
7. My present thinking about a dog is intrinsically intentional, intrinsically object-directed. But no physical state is intrinsically object-directed. So, by the Indiscernibility of Identicals, my present thinking about a dog simply cannot be identical to any brain state, and so cannot reduce to any brain state. Kim of course thinks that intentional properties are functionalizable. I have already argued against that view here. Whatever causal role my thinking about a dog plays in terms of behavioral inputs and outputs, causal role occupancy cannot be make makes my thinking intentional. For it is intentional intrinsically, not in virtue of causal relations.
8. Kim speaks of the functional reducibility of intentional/cognitive properties. But surely it is not properties that need reducing but particular meetal acts. Properties are not conscious of anything. Nor are causal roles. It is the realizers of the roles that are bearers of intentionality, and it simply makes no sense to think of these as purely physical.
9. Once one starts down the reductive road there is no stopping short of eliminativism. The latter, however, is surely a reductio ad absurdum of physicalism as I explain in this post on Rosenberg's eliminativism.
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