This chapter considers the conceivability argument against physicalism. It focuses on positive rather than negative conceivability. This is an important limitation, but a discussion of arguments making use of positive conceivability is still of significance. First, positive conceivability is important in its own right. Second, arguments which rely on negative conceivability require a reason to think that negative conceivability provides a good guide to metaphysical possibility. This claim is controversial: it in effect requires what is metaphysically possible to be accessible through a priori reflection on a limited number of truths. In imagining a situation, philosophers can distinguish between qualitative and stipulative content. It is worth comparing extension rules with other proposed limitations on the connection between imagination and possibility. The chapter argues that anti-physicalist situations involve stipulative content and that for each anti-physicalist situation we lack an extension rule to support this content.