Mereology is not a Guide to (In)conceivability

A sophisticated version of the zombie argument due to David Chalmers runs roughly as follows: a zombie world is ideally primarily conceivable, and whatever is ideally primarily conceivable is primarily possible. Thus, a zombie world is primarily possible, which implies, in turn, that either physicalism is false or Russellian monism is true. Appealing to some plausible mereological considerations, Daniel Giberman presents a novel argument to the effect that zombies are not ideally primarily conceivable. I shall argue, firstly, that a main premise of Giberman's argument is ill-supported, as it trades on a confusion between the primary and the secondary intensions of the "actually" operator. I then consider two lines of reasoning, which might be extracted from Giberman's text, in favour of another chief premise of his argument. I shall argue that the first line of reasoning is flawed, and the second one, in effect, will transform Giberman's argument into a kind of "parity argument" in which his mereological considerations play no role.