Since the publication of the Philosophical Investigations in 1953, Wittgenstein's later philosophy of mind has been the subject of numerous books and articles. Although most commentators agree that Wittgenstein was neither a behaviorist nor a Cartesian dualist, many continue to ascribe to him a position that strongly resembles one of the alternatives. In contrast, this paper argues that Wittgenstein was strongly opposed to behaviorism and Cartesianism, and that he was concerned to show that these positions implicitly share a problematic assumption. This assumption is a seemingly innocent idea that subjectivity, or mind, is some kind of object or thing. The paper provides a detailed survey of Wittgenstein's critique of Cartesianism and behaviorism, as well as an outline of Wittgenstein's alternative account of subjectivity.