  Both metaphysical and empirical arguments have been given in support of such claims. Among the former are those that appeal to intuitions about the conceivability and logical possibility of zombies, i.e., of beings whose behavior, functional organization, and physical structure down to the molecular level are identical to those of normal human agents but who lack any qualia or qualitative consciousness. Some (Kirk 1970, Chalmers 1996) assert such beings are possible in worlds that share all our physical laws, but others deny it (Dennett 1991, Levine 2001). If they are possible in such worlds, then it would seem to follow that even in our world, qualia do not affect the course of physical events including those that constitute our human behaviors. If those events unfold in the same way whether or not qualia are present, then qualia appear to be inert or epiphenomenal at least with respect to events in the physical world. However, such arguments and the zombie intuitions on which they rely are controversial and their soundness remains in dispute (Searle 1992, Yablo 1998, Balog 1999).