This is a selection from a long article in a reference work. I’ll provide some information from the article below; but, if you want to know more, you can find it on line at http://consc.net/papers/nature.html or http://consc.net/papers/nature.pdf.

Before this selection begins, Chalmers has noted three arguments for consciousness or against materialism that correspond, more or less, to the three sorts of arguments that van Gulick considered (see pp. 664-670). He then identifies six types of response to the these arguments. The first three are materialist replies to the arguments and the rest are ways of rejecting materialist reduction (two sorts of dualism—interactionism and epiphenomenalism—and a form of monism according to which phenomenal properties constitute “the intrinsic nature of the physical”). Of the three materialist responses, “type-A” is the firmest rejection of the arguments, holding, for example, that Mary learns no truths and that zombies are inconceivable while “type-C” holds that things of this sort could come to be so as our thinking develops. The third type, “type-B,” is the one that Chalmers discusses in this selection, which includes all of his discussion of it.

Although Chalmers is concerned with issues that are close to those we discussed last week, it is a less explicit tie with Lycan’s discussion that is the main reason for reading him now. HOR theories of consciousness model it on our perceptual and cognitive relation to the external world. The latter relation is associated with the possible disconnnects that lead to Twin-Earth examples and externalism more generally. Saul Kripke, who was, along with Putnam, responsible for calling attention to these issues held that there was nothing analogous in the case of consciousness. Chalmers shares that view and bases his discussion of “type-B” materialism on it. So you should watch for references to Kripke and this range of issues. One key point is not emphasized by Chalmers: don’t underestimate the significance of the argument in the paragraph on p. 599 beginning “First, Q.”

Chalmers uses some basic logical notation: “P ⊃ Q” amounts to “if P then Q” and “P&~Q” amounts to “P but not Q.” Chalmers’ “two-dimensional semantics” is also somewhat technical. It is enough to see the point of the less technical presentation of the ideas in the two paragraphs beginning at the end of column 1 of p. 598.