Grazer Philosophische Studien 61 (2001) 249-255
PRECIS OF PSYCHONEURAL REDUCTION: THE NEW WA VE
John BICKLE University of Cincinnati
Although her plumb for eliminative materialism generated the most sound and fury, three other projects in Patricia Churchland's (1986) Neurophilosophy were of greater philosophical significance:
Contributing to a new theory of cross-levels intertheoretic reduc- tion for science in general and reformulating the traditional mind-body problem using these resources; Replying to dualists' arguments based on features of conscious ex- perience (qualia, subjectivity); Replying to multiple realizability arguments for both functionalism and the methodological autonomy of cognitive psychology from the neurosciences.
Churchland did not invent any of these projects, but her book gave them a unified focus grounded on a post-logical empiricist philosophy of science and a wealth of empirical neuroscientific detail. Unfortunately, these three projects and the progress Church land and other reductionists made got lost in the bombast over eliminativism. By the late-1990s interest in eliminativism had waned, but recent de- velopments in philosophy of mind had also eclipsed these specific pro- jects. Some flaws in the theory of intertheoretic reduction remained unad- dressed. (Clifford Hooker 1981 had first noticed these in the very paper that remained the benchmark for the theory.) New "dualistic" arguments based on more sophisticated metaphysics emerged (Chalmers 1996), along with "New Mysterian" worries about humans' capabilites of solv- ing the consciousness-brain problem (McGinn, 1989). Nonreductive physicalism replaced functionalism, and supervenience replaced realiza- tion as the preferred alternative to reduction. Clearly, if "neurophiloso- phy" was to remain viable, these three projects and their unity within a philosophy of science and the empirical neurosciences required reformu- 250 lation and a new focus. I wrote Psychoneural Reduction: The New Wave (Bickle 1998) to pro- vide this. The book begins with a puzzle and a dilemma about orthodox cognitivism and nonreductive physicalism. The puzzle concerns super- venience. Can it really ground a physicalism about mind? Even its history would suggest not. G.E. Moore introduced the concept (though not the term) into philosophy to ground a non-natural ethics. The closely-related dilemma concerns ontology and one's preferred cross-levels relation. The more that cognitivists and nonreductive physicalists stress the nonreduc- tive aspects of their methodology and relation, the more their position re- sembles traditional property dualism. The more they stress physicalism to avoid this slide, the more their methodology and relation resembles reductionism - at least intuitively. Reductionists don't win by this gambit, however. They owe a theory of this relation consistent with historical cases and the sense that pervades contemporary neuroscience, but which avoids the counterarguments that sunk "classical" psychoneural reduction. Clifford Hooker's (1981) theory of intertheoretic reduction provides some key insights. Hooker maintains that reduction involves deduction, but not of the reduced theory TR from the reducing ("basic") theory TB (as the classical "Nagelian" logical em- piricist view holds). Instead, what gets deduced is an image TR * of TR spec- ified within the framework and vocabulary of TB• This change renders tractable some famous problems for the classical account. It also yields a spectrum of possible reduction relations, depending upon the "closeness" of the "analog relation" obtaining between TR * and TR and the number and "counterfactual nature" of limiting assumptions or boundary conditions necessary to derive a TR* with that "degree of fit." We can then construct two. spectra out of historical reduction cases: the intertheoretic reduction spectrum just described, from "smooth" to "bumpy;" and the ontological consequences spectrum, from "cross-theoretic identities" through "con- ceptual change" to "outright elimination" of the ontology affiliated with
TR• A given reduction's locations on these two spectra are by and large iso- morphic.1 This discovery suggests a strategy for exploring the ontological consequences of potential or developing reductions. Investigate where on the intertheoretic reduction spectrum the case appears to be headed. The isomorphic location on the ontological consequences spectrum then pro- vides the answer. Reformulating the traditional mind-body problem into an intertheoretic reduction issue for psychology and neuroscience brings
1. This point is illustrated in Bickle (1998), Figure 2., p. 30.