 Recently, this standard assessment has been challenged. In his important 2010 book and other publications, Tim Bayne suggests that there are not two centres of consciousness. There is just one. What explains the appearance of duality is that this single centre of consciousness switches in the material of which it is consciousness from one hemisphere to the other. He calls this the switch model (2010: chs 8.4 and 9.5). To so much as get this approach off the ground, it is crucial that that there be little or no evidence of a centre of consciousness that is conscious of, say, A, B, and C but not D, E, and F and at the same time of a centre of consciousness that is conscious of D, E, and F but not A, B, C. What we just called the standard assessment starts from a belief that there is lots of such evidence. Bayne disagrees. We will return to Bayne’s view in  Section 4.2.