Dualism: Any philosophical theory that posits two distinct primary substances or that is built around a fundamental distinction between two elements. The term is used in a variety of contexts to designate entirely different kinds of theories. For example, ancient Manichaeism was a form of dualism postulating two equal but opposing divine realities, a good power of light and an evil power of darkness. Theism has a dualistic dimensionin that it makes a clear distinction between God and the created order, between the infinite and the finite. Theories positing that the mind (or soul) and the body are distinct substances are also referred to as dualisms, though there are important differences among Platonic, Thomistic and Cartesian forms of mind-body dualism.1
1. C.Stephen Evans, Pocket Dictionary of Apologetics & Philosophy of Religion (Downers Grove, IL: InterVarsity Press, 2002), pp. 36-37.