Shapiro, L. A., & Polger, T. W. (2012). Identity, variability, and multiple realization in the special sciences. New Perspectives on Type Identity: The Mental and the Physical (pp. 264-88).
Compositional variation and variability in nature is abundant. This fact is often thought to entail that multiple realization is also ubiquitous. In particular, compositional variability among cognitive creatures is thought to provide conclusive evidence against the mind-brain type identity theory. In this chapter we argue that the type identity theory, properly understood, is compatible with a wide range of compositional and constitutional variation and variability. Similarly, contrary to received wisdom, variation poses no threat to reductionist ventures. Multiple realization as we understand it, requires a specific pattern of variation. Multiple realization is not self-contradictory; the kinds of variation that qualify as multiple realization are not impossible, but they are less common in general than is widely supposed.
Citing Place (1956) in context (citations start with an asterisk *):
I. Introduction
* When the early identity theorists, e.g. U.T. Place, Herbert Feigl, and J. J. C. Smart, first gave voice to the idea that mental events might be identical to brain processes, they had as their intended foil the view that minds are immaterial substances. [...] Place, Feigl, and Smart need not be thought of as endorsing some of the monolithic claims that are often associated with identity and reduction. [...] Seeing how Place, Feigl, and Smart thought about scientific identities will help us understand the identity theory's relationship to reductionism and the extent to which the possibility of multiple realization poses a threat.
Section II. The Identity Theory
* According to the textbook view, Place, Feigl, and Smart, the fathers of the identity theory, argued that mental kinds are identical to physical kinds.
* [...] the identity theorists [...] took themselves to be challenging dualism or, more generally, the belief that [...] the mental exists independently of the physical. Place for example, warns against conceiving of mental events as taking place in a "mysterious internal environment" (1956: 55) [this should be p. 44].
* Quite plausibly, U. T. Place would not endorse the type-identity claim in its post-Kripkean form. One reason is that he seems to have been genuinely committed to the idea that the mind-brain relation is contingent. However, once Kripke cleared the way for a category of the necessary a posteriori, the identity theorist has the option of giving up the contingency claim (Lycan 1987: 19-21; Polger 2010). And the arguments employed by Feigl and Smart suggest that they should take that option. Place, on the other hand, never construed scientific identities in quite the same way as the other two (1960, especially footnote 5). And, although all three believed psychophysical identities to be contingent, Place explicated the relation on the model of material composition, which is asymmetric and (he seems to have thought) contingent. He himself holds that this compositional “identity” is the best explanation for the correlation of observations of mental states with observations of brain states. The 'is' of psychophysical identities, Place tells us, is neither the 'is' of definition (A square is an equilateral rectangle”), nor of predication (“Her hat is red”), but of composition: “Her hat is a bundle of straw tied together with string” (1956: PPP).
* In contrast to Place, Smart seems like a plausible candidate for endorsing a post-Kripkean identity theory, one that takes mind-brain identities to be necessary a posteriori.
* It is common to portray the identity theory as committed to a view of the world according to which mental kinds are identified with homogenous brain state kinds, and brain state kinds with homogenous biochemical kinds, and so on,… all the way down (Figure 1). If so, then any heterogeneity at any step of this “stovepipe” reduction would falsify the identity theory. [...] Yet, the "stovepipe" view is absurd and to think that Place, Feigl, Smart or any identity theorist has ever held it is uncharitable at best.
* If we believed the fable [that any variability decisively refutes the identity theory], we should be surprised to discover that Place, Feigl, and Smart all discussed cases of compositional variation.
* When re-reading the original papers of Place, Smart, and Feigl, one cannot help but suspect that the canonical interpretation of their ideas has been unfair. Far from being a slow and wounded stag that the arrow of multiple realization might easily bring down, the identity theory, as originally presented, proposed a versatile and prescient conception of the relation between the mind and the brain.
Citing Place (1960) in context (citations start with an asterisk *):
see citation of Place (1956)