This entry concerns dualism in the philosophy of mind. The term ‘dualism’ has a variety of uses in the history of thought. In general, the idea is that, for some particular domain, there are two fundamental kinds or categories of things or principles In theology, for example a ‘dualist’ is someone who believes that Good and Evil—or God and the Devil—are independent and more or less equal forces in the world. Dualism contrasts with monism, which is the theory that there is only one fundamental kind, category of thing or principle; and, rather less commonly, with pluralism, which is the view that there are many kinds or categories.