 We won’t discover that generalization, however, if we focus on the person’s neurophysiology and resulting muscular contractions. That level of explanation logically is too weak, for it cannot tell us that the prior sequence of neural events and muscular contractions will lead to the subsequent action of dialing another 1. A physiological explanation for any given instance will only link one way of learning the emergency phone number to one way of coming to know that an emergency occurred to one sequence of neural events and resulting muscular contractions producing the behavior (nonintentionally described). However, the number of physical events constituting each of these cognitive classes—the learning, the coming to know, and the action of dialing—is potentially unlimited, with the constituents of each class often unrelated to each other at the physiological level of description. (This is Pylyshyn’s appeal to multiple realizability.) So if there is a generalization at the higher level of description available for capturing—and in the example sketched above, surely there is—an exclusively reductionist approach to psychological explanation will miss it. Thus because of multiple realizability, reductionism violates a tenet of scientific methodology: seek to capture all capturable generalizations. Such methodological arguments did not end with Pylyshyn’s. Fodor (1975: Chapter 5) and Terence Horgan (1993) raise related methodological caveats about reductionism based on multiple realizability. Bickle (1998: Chapter 4) responds directly to these.