The Functional Unity of Special Science Kinds
The view that special science properties are multi ply realizable has been attacked in recent years by Shapiro, Bechtel and Mundale, Polge r, and others. Focusing on psychological and neuroscientific properties, I argue that these attacks are unsuccessful. By drawing on interspecies physiological comparisons I show that diverse physical mechanisms can converge on common functional properties at multiple levels. This is illustrated with examples from the psychophysics and neuroscience of early vision. Thi s convergence is compatible with the existence of general constraints on the evolution o f cognitive systems, and does not involve any ad hoc typing of coarse-grained higher level properties. The mechanisms that realize these common higher level properties are really distinct by he criteria laid down by critics of multiple realizability. Finally, I present an account of how such functional properties might constitute special science kinds by playing a central explanat ory role in a range of cognitive models. Behavioral science kinds in particular are the func tionally defined constituents picked out by our most successful models of the multilevel systems an d mechanisms that explain cognitive capacities. 1 Reduction versus elimination, redux 2 The eyes of others 3 Unity through constraint? 4 Justifying taxonomic mismatches 5 Further conditions on multiple realization