 Special factors. It has been suggested that there are special factors at work in the psychophysical case which have a strong tendency to mislead us. For example it is claimed that what enables us to imagine or conceive of states of consciousness is a different cognitive faculty from what enables us to conceive of physical facts: ‘there are significant differences between the cognitive factors responsible for Cartesian intuitions [such as those about zombies] and those responsible for modal intuitions of a wide variety of other kinds’ (Hill and McLaughlin 1999, p. 449. See also Hill 1997). The suggestion is that these differences help to explain the ease with which we seem able to conceive of zombies, and the difficulty we have in understanding the claim that they are nevertheless impossible.