The Absentminded Professor

In this paper, I argue that absences pose a challenge to our understanding of physicalism that has not been properly appreciated. I do this by setting out a thought experiment involving a being in whom absence properties occupy the causal roles that functionalists take to define mental properties, in which case these absence properties realize the being’s mental properties. Such a being should be compatible with the truth of physicalism, I argue, even though its mental properties are neither themselves physical properties nor are they realized/grounded in physical properties—instead, they are realized/grounded in (nonphysical) absence properties. I argue that the case serves as a counterexample to leading formulations of physicalism that appeal to realization or grounding, but not to standard supervenience-based formulations of physicalism, because the latter typically include negative truths in their supervenience base in addition to physical truths. I show how realization- and grounding-based formulations of physicalism might be revised to handle the problem, but also recommend that we rethink how we understand physicalism and the role that negative entities can play for physicalists.