dualism the view that reality consists of two disparate parts. The crux of dualism is an apparently unbridgeable gap between two incommensurable orders of being that must be reconciled if our assumption that there is a comprehensible universe is to be justified. Dualism is exhibited in the pre-Socratic division between appearance and reality; Plato’s realm of being containing eternal Ideas and realm of becoming containing changing things; the medieval division between finite man and infinite God; Descartes’s substance dualism of thinking mind and extended matter; Hume’s separation of fact from value; Kant’s division between empirical phenomena and transcendental noumena; the epistemological double-aspect theory of James and Russell, who postulate a neutral substance that can be understood in separate ways either as mind or brain; and Heidegger’s separation of being and time that inspired Sartre’s contrast of being and nothingness. The doctrine of two truths, the sacred and the profane or the religious and the secular, is a dualistic response to the conflict between religion and science. Descartes’s dualism is taken to be the source of the mind–body problem. If the mind is active unextended thinking and the body is passive unthinking extension, how can these essentially unlike and independently existing substances interact causally, and how can mental ideas represent material things? How, in other words, can the mind know and influence the body, and how can the body affect the mind? Descartes said mind and body interact and that ideas represent material things without resembling them, but could not explain how, and concluded merely that God makes these things happen. Proposed dualist solutions to the mind–body problem are Malebranche’s occasionalism (mind and body do not interact but God makes them appear to); Leibniz’s preestablished harmony among noninteracting monads; and Spinoza’s property dualism of mutually exclusive but parallel attributes expressing the one substance God. Recent mind–body dualists are Popper and John C. Eccles. Monistic alternatives to dualism include Hobbes’s view that the mental is merely the epiphenomena of the material; Berkeley’s view that material things are collections of mental ideas; and the contemporary materialist view of Smart, Armstrong, and Paul and Patricia Churchland that the mind is the brain. A classic treatment of these matters is Arthur O. Lovejoy’s The Revolt Against Dualism.
Dualism is related to binary thinking, i.e., to systems of thought that are two-valued, such as logic in which theorems are valid or invalid, epistemology in which knowledge claims are true or false, and ethics in which individuals are good or bad and their actions are right or wrong. In The Quest for Certainty, Dewey finds that all modern problems of philosophy derive from dualistic oppositions, particularly between spirit and nature. Like Hegel, he proposes a synthesis of oppositions seen as theses versus antitheses. Recent attacks on the view that dualistic divisions can be explicitly described or maintained have been made by Wittgenstein, who offers instead a classification scheme based on overlapping family resemblances; by Quine, who casts doubt on the division between analytic or formal truths based on meanings and synthetic or empirical truths based on facts; and by Derrida, who challenges our ability to distinguish between the subjective and the objective. But despite the extremely difficult problems posed by ontological dualism, and despite the cogency of many arguments against dualistic thinking, Western philosophy continues to be predominantly dualistic, as witnessed by the indispensable use of two-valued matrixes in logic and ethics and by the intractable problem of rendering mental intentions in terms of material mechanisms or vice versa.
See also METAPHYSICS , PHILOSOPHY OF MIN. R.A.W.