How to Keep the ' Physical ' in Physi ( : Alism

THEJOURNAL OF PHILOSOPHY HOW TO KEEP THE 'PHYSICAL' IN PHYSI(:ALISM* Physicalism is roughly the thesis (1) that every entity is either itself a physical entity or is exhaustively composed, ultimately, of physical entities, and (2) that every property is either itself a physical property or is realized, ultimately, by physical properties.l Never mind whether exhaustive composition and realization are the best notions for a physicalist to employ in explicating the idea that everything is physical better, for instance, than the notions of token identity and supervenience;2 and never mind also how these notions are to be precisely understood. The problem I wish to discuss is what physicalists can and should mean by 'physical' in their formulations of physicalism, and this problem arises on any reasonable view as to the answers to these questions. A physicalist's definition of 'physical' can perfectly well be stipulative the problem is not one of conceptual analysis but to be plausible it must at least meet the following two conditions: when plugged into an otherwise satisfactory formulation of physicalism, it must yield a thesis (1) that is not obviously false and (2) that possesses content determinable by us. (A physicalism whose content was not determinable by us would presumably be impossible for us to support empirically, and might, for all we know, not even exclude from existence the sort of paradigmatically nonphysical items for example, souls, entelechies, ghosts which physicalists have traditionally refused to countenance.) There is a dilemma, however, apparently owed to Carl G. Hempel,3 that is sometimes thought to show that no physicalist definition of 'physical' can