What is Physicalism?
Suppose for the sake of argument that panpsychism is true. Suppose also that a physicist investigating panpsychism finds evidence of its truth in the form of anomalous motions of elementary particles—motions that cannot be explained by the usual forces. She formulates a “psychic-field theory” that postulates a force field analogous to the electromagnetic field, even supplying some equations relating psychic magnitudes to motions of particles. The theory is tested and confirmed. Another physicist makes a refinement to the original theory, improving its predictive power, perhaps integrating the theory with standard electromagnetic theory (though not yet with general relativity). We now have a theory postulating an array of basic psychic properties possessed by particles, mathematically expressed, and confirmed by experiment. These properties are given technical names, deriving from vernacular terms like “pain”, “seeing red”, and “anger”—say, “pin”, “seer”, and “rage”. Particles are said to have the corresponding properties in varying magnitudes—so the electron has, say, “two hundred Julies of rage” (Julie was the physicist who first detected the properties in question). In due course the new theory becomes orthodox and textbooks include it routinely. There is also a terminological shift prompted by the misleading associations of the word “psychic”, which suggests some unscientific mumbo-jumbo involving seeing the future. The properties in questions are called instead “qualia” and the theory is called “qualia field theory” (it is generally accepted that qualia are close cousins of ordinary states of the human mind, though simpler). The physicist who originated the theory is duly awarded the Nobel Prize for physics, and physics enters a new and exciting phase in its long development. Where once we added electromagnetic theory to gravitation theory, thus expanding the domain of physics, now we add qualia theory to what physics already recognizes to exist—so obtaining a more comprehensive and predictive theory. In the fullness of time popular physics books appear in which the new theory is explained and extolled, with titles like How Julie Revolutionized Physics.
Question: Would this story show that the mind is physical? Would it vindicate the metaphysical doctrine known as “physicalism”? Has the theory of panpsychism been shown to be a physicalist theory? As I told the story, the qualia theory becomes part of physics—it is developed by people called physicists and taught in departments called physics departments. But does it vindicate the philosophical doctrine known as “physicalism”—intended as a form of monism opposed to dualism, touted as promoting “desert landscapes”, “metaphysical naturalism”, and “hard-headed materialistic ontology”? I think it is clear that it does not: it merely incorporates mental properties into a science that specializes in fundamental features of the world treated mathematically. In the same way, the introduction of electromagnetic theory into physics did not vindicate a “physicalist” metaphysics of electricity and magnetism, as opposed to a “dualist” metaphysics of these things; it simply rendered a real set of phenomena treatable by the methods used in the science known as physics. There was no reduction of electromagnetism to gravitation, still less to classical mechanism; and there was no reduction of (so-called) psychic properties in my story to properties already recognized in physics. Heterogeneity reigns in physics, in its actual history and in my hypothetical history. Maybe for boring institutional and cultural reasons the basic psychic properties will come to be called “physical”, as happened in the case of electromagnetic properties; but no deep metaphysical theory is confirmed by such a linguistic move. To be incorporated into physics is not to be shown to be “physical”. A metaphysical dualist could, with equal right, say that my story shows that physics must recognize irreducibly psychic properties—so that physics must include more than the physical. In fact, the dualist might insist, physics is wrongly so named: it should really be called “psychics”, since it deals with irreducibly psychic properties (among others).
What I think we should conclude is that the whole idea of “physicalism” is neither helpful nor meaningful. Whether the world contains certain properties that can be treated by the methods of physics is a genuine question, but trying to decide whether these properties are “physical” or “non-physical” is a pointless enterprise. We shouldn’t even be asking if the mind is “physical”, pending some clarification of what we wish to mean by this term. The word is more a term of approbation than it is descriptive of a significant metaphysical category. This is why Julie herself would never answer the question of whether her discovery vindicated materialism or immaterialism. Her opinion was that it vindicated neither, the entire question being misconceived.