1911 Encyclopædia Britannica/Monad
MONAD (Gr. μονάς, unit, from μόνος, alone), a philosophic term which now has currency solely in its connexion with the philosophy of Leibnitz. In the earlier Greek philosophy the term meant unity as opposed to duality or plurality; at a later time it meant an individual, or, with the Atomists, an atom. It was first used in a sense approximate to that of Leibnitz by Bruno, who meant by it a primary spiritual element as opposed to the material atom. Leibnitz, however, seems to have borrowed the term not directly from Bruno, but from a contemporary, Van Helmont the younger. Leibnitz's view of things is that the world consists of monads which are immaterial centres of force, each possessing a certain grade of mentality, self-contained and representing the whole universe in miniature, and all combined together by a pre-established harmony. Material things, according to Leibnitz, are in their ultimate nature composed of monads, each soul is a monad, and God is the monas monadum. Thus monadism, or monadology, is a kind of spiritual atomism. The theory has been revived in recent years by C. B. Renouvier.