Almost twenty years ago, Carl Hempel posed a dilemma for those attempting to define the physical in reference to microphysics. On the one hand, it seems that we cannot define the physical in terms of current microphysics since today's principles of microphysics are, most likely, not correct. Despite some physicists' heady optimism that the end of physics is just around the corner, history cautions prudence... Yet on the other hand, if we take microphysics to be some future unspecified theory, the claim that the mind is physical is extremely vague since we currently have no idea of what that theory is. Geoffrey Hellman sums up this dilemma nicely: "either physicalist principles are based on current physics, in which case there is every reason to think they are false; or else they are not, in which case it is, at best, difficult to interpret them, since they are based on a 'physics' that does not exist." Faced with this dilemma, what is a physicalist to do?
Barbara Montero, "The Body Problem"