<p><strong>Noun:</strong></p><ul><li>The state of being dual or consisting of two parts; division into two.</li><li><strong>Philosophy:</strong> The view that there are just two mutually irreducible substances. Compare monism, pluralism.</li><li>The view that substances are either material or mental.</li><li><strong>Theology:</strong> The doctrine that there are two independent divine beings or eternal principles, one good and the other evil.</li><li>The belief that a human being embodies two parts, as body and soul.</li></ul>