My aim is to rekindle interest in David Lewis's (1983) infamous but neglected Mixed Theory of mental states. The Mixed Theory is a mix of physicalism and functionalism designed to capture the intuitions that both Martians and abnormal human Madmen can be in pain. The Mixed Theory is widely derided. But I offer a new development of the Mixed Theory immune to its most prominent objections. In doing so, I uncover a new motivation for the Mixed Theory: its unique ability (...) to explain cases in which it is plausibly indeterminate whether something is in pain. The Mixed Theory, whether or not it is ultimately correct, at least deserves renewed attention. (shrink)