Chapter 2: Kim’s causal exclusion argument against non-reductivism
2.2 A summary of Kim’s exclusion argument
2.2.4 Kim’s solution to the paradox of the exclusion argument
Kim’s exclusion argument was presented as a reductio against the Distinctness premise, against non-reductive physicalism. In case one is committed to physicalism (Closure and Supervenience), and aims to preserve mental causation, this seems to be the only path to follow. Multiple realizability leaves us with a dilemma: either we should deny physicalism because there are efficacious non-physical properties irreducible to lower-level properties, or higher-level properties are inefficacious, and so epiphenomenal. The latter option is what we wanted to avoid in the first place, the former requires us to give up on physicalism. Therefore, as physicalists we are forced to find a way to reconcile mental causation with physicalism.
“What we want — at least, what some of us are looking for — is a philosophical account of how it [mental causation] can be real in light of other principles and
truths that seem to be forced upon us.” (Kim 1998:72, my italics)
In Kim’s view, to preserve mental causation via some kind of reduction offers the best deal. But before accepting such a deal he has to offer us some satisfactory answer that can accommodate our convictions concerning Distinctness as well. We can’t just give up on Distinctness without a satisfactory bargain. Epiphenomenalism can’t work, mental causation should be preserved, but if one lacks the resources to properly argue against multiple realization then some explanation or an error theory of multiple realizability claims and our intuitions concerning Distinctness is required. Or, in other words, there should be a satisfactory answer to the question, what makes special science statements, like those of psychology or even statements of macro-level physics true or useful?
What is nice about Kim’s approach to the problem of mental causation is that he has an answer to this question, whether we like it or not. He accepts the challenge from Fodor
and Putnam and agrees that it is not possible to find a single broadly physical, complex neural property shared by all organisms experiencing pain. But instead of accepting that pain is a realization-independent mental property he went for the elimination of this generic, unified property and replaced it with so-called local, species-specific mental properties (Kim 1992). Such properties are reducible to their neural bases.
So, there is pain-in-humans, pain-in-foxes, pain-in-magpies, but there is no species or structure independent pain as such. As pain-in-humans is identical to some specific kind of neural realizer (probably a set of satisfactorily homogeneous particular realizers) the causal powers of pain-in-humans are identical with those of the realizer. The same goes for all such species-specific mental properties.
So, on the one hand Kim is a reductionist and on the other hand a revisionist eliminativist as well, as he thinks that there is no such thing as a generic mental property pain. It is fair to ask at this point, where is the explanation for our intuition concerning Distinctness? His answer is that even though there is no generic pain property behind it, we have a generic concept of pain. This concept is useful as it encompasses a group of phenomena that stand in some kind of family resemblance relationship to each other, but closer attention shows us that the different species-specific pains are causally heterogeneous to a large extent31. This
view is a consequence of another view he holds. On Kim’s account of higher-level physically realized properties they inherit their causal powers form their realizers. The causal powers of a higher-level property instance are the same as the causal powers of its realizer. As
31 Even though the idea is applied in a piecemeal manner this approach is close to Heil’s, according to which the
mental-physical disctinction is not onologically deep, as it is a difference in conception only. He emphasises the distinction between predicates and properties (Heil 2013). Predicates might refer to properties but usually they do not, as in the case of mental discourse. But predicates might have truth-makers independently of this issue.
supervenience is a weak principle and probably insufficient for physicalism Kim supplemented it with the principle of causal inheritance32 to guarantee a metaphysically serious connection
between realized and realizer properties. As there are interesting physical differences between different realizer properties, on grounds of this principle we are forced to think that the realized property instances are causally heterogeneous. If respectable scientific kinds are individuated on grounds of their causal powers, as both Fodor and Kim agreed, realized properties with physically diverse realizers are unfit candidates. The concept of pain remains meaningful as a synonymy class of relatively diverse predicates, but not as something that pics out a proper scientific kind.
This answer is satisfactory in the sense that it accounts for the underlying convictions that make Distinctness plausible for us and allows for causally efficacious mental properties at the same time. Local, domain specific reductions eliminate the problem created by distinctness on pain of the reconceptualization of multiply realized kinds. Higher-level kinds are mere concepts, as these kinds are causally heterogenous. They are not proper scientific kinds as such.