  A variety of arguments have been given in favor of dualist and other anti-physicalist theories of consciousness. Some are largelya priori in nature such as those that appeal to the supposed conceivability of zombies (Kirk 1970, Chalmers 1996) or versions of the knowledge argument (Jackson 1982, 1986) which aim to reach an anti-physicalist conclusion about the ontology of consciousness from the apparent limits on our ability to fully understand the qualitative aspects of conscious experience through third-person physical accounts of the brain processes. (See Jackson 1998, 2004 for a contrary view; see also entries on  zombies,  and  qualia: the knowledge argument.)  Other arguments for dualism are made on more empirical grounds, such as those that appeal to supposed causal gaps in the chains of physical causation in the brain (Eccles and Popper 1977) or those based on alleged anomalies in the temporal order of conscious awareness (Libet 1982, 1985). Dualist arguments of both sorts have been much disputed by physicalists (P.S. Churchland 1981, Dennett and Kinsbourne 1992).