Many contemporary philosophers of mind are concerned to defend a thesis called a posteriori physicalism. This thesis has two parts, one metaphysical, and the other epistemological. The metaphysical part of the thesis—the physicalist part—is the claim that the psychological nature of the actual world is wholly physical. The epistemological part of the thesis—the a posteriori part—is the claim that no a priori connection holds between psychological nature and physical nature. Despite its attractiveness, however, a familiar argument alleges that a posteriori (...) physicalism cannot be true. This argument is sometimes called the Property Dualism Argument Against Physicalism. In this paper, I consider Stephen White’s version of the Property Dualism Argument and argue that it fails. I distinguish two ways in which the argument’s crucial notion might be understood, and I argue that on neither way of understanding it is the Property Dualism Argument compelling. (shrink)