Definition of: dualism

(d′əl·iz′əm, dy′-) noun
1. The state of being twofold; duality.
2. A system or theory which asserts a twofoldness of nature, being, or operation; specifically, theological dualism, or the doctrine that there are two eternal and opposing principles, or beings, one good and the other evil; philosophical dualism, or the theory that the nature of the universe is twofold, i.e., comprised of mind and matter, as opposed either to idealistic or materialistic monism; psychological or psychophysical dualism, the theory that the body and mind of man are two different existences but are placed by the order of nature in a most intimate system of correlations or interactions; or ethical dualism, the system of morals which demands and justifies one kind of conduct toward one's fellows in the same social group and another kind of conduct toward other men.
3. Gram. The expression of the condition of duality.