Physicalism

In the sense relevant to this article, physicalism (or materialism; the two terms are used interchangeably in the literature) is a comprehensive view about the nature of the world to the effect that every phenomenon whatever is, or is at bottom, physical. As such, it obviously raises issues about the place of phenomenal consciousness, intentionality, and morality—among other things—in a purely physical world. But it also raises issues that are independent of these familiar special cases, and it is to them that this article is devoted. One cluster of issues concerns how to formulate a thesis of physicalism that is neither obviously true nor obviously false, and significant if true. This has generally been thought to require specifying (1) a narrow sense of “physical,” perhaps linked to physics, and (2) some relation of being nothing over and above such that phenomena that are not physical in the narrow sense can be claimed to be nothing over and above phenomena that are physical in the narrow sense; candidates for such a relation are identity, supervenience, realization, and, most recently, grounding. A second cluster of issues concerns the implications of physicalism. Is physicalism a posteriori? Is it (if true at all) necessarily true? Can physicalism avoid commitment to physical reductionism? If so, how, and if not, then is that a problem for physicalism? Is physicalism consistent with the countless claims of causation and causal explanation made in the special sciences and in everyday life? (This last issue overlaps so much with the problems of mental causation, which have a vast literature of their own, that it is not addressed in the present article; the reader is directed to the separate article on mental causation.) A third cluster of issues concerns how in principle we could have, and whether in fact we do have, empirical evidence that physicalism is true—or of course that it is false. For example, is it true that for every (narrow sense) physical effect there is a sufficient physical cause, that is, that the causal closure of the physical holds? And if it does, then can a case for physicalism be built upon it? Can observed correlations between reported mental states (say) and brain states provide reason to think that mental states just are brain states? A fourth cluster of issues concerns alternatives to physicalism. Aside from traditional forms of mind-body dualism, what possible alternatives are there? For example, panpsychism holds that phenomenal properties are the intrinsic aspects of the properties known in physics through their causal or structural aspects. Is this a physicalist view or not? What scope is there for theses of pluralism, or of neutral monism?