occasionalism a theory of causation held by a number of important seventeenth-century Cartesian philosophers, including Johannes Clauberg (1622–65), Géraud de Cordemoy (1626– 84), Arnold Geulincx (1624–69), Louis de la Forge (1632–66), and Nicolas Malebranche (1638–1715). In its most extreme version, occasionalism is the doctrine that all finite created entities are devoid of causal efficacy, and that God is the only true causal agent. Bodies do not cause effects in other bodies nor in minds; and minds do not cause effects in bodies nor even within themselves. God is directly, immediately, and solely responsible for bringing about all phenomena. When a needle pricks the skin, the physical event is merely an occasion for God to cause the relevant mental state (pain); a volition in the soul to raise an arm or to think of something is only an occasion for God to cause the arm to rise or the ideas to be present to the mind; and the impact of one billiard ball upon another is an occasion for God to move the second ball. In all three contexts – mind–body, body–body, and mind alone – God’s ubiquitous causal activity proceeds in accordance with certain general laws, and (except for miracles) he acts only when the requisite material or psychic conditions obtain. Less thoroughgoing forms of occasionalism limit divine causation (e.g., to mind–body or body–body alone). Far from being an ad hoc solution to a Cartesian mind–body problem, as it is often considered, occasionalism is argued for from general philosophical considerations regarding the nature of causal relations (considerations that later appear, modified, in Hume), from an analysis of the Cartesian concept of matter and of the necessary impotence of finite substance, and, perhaps most importantly, from theological premises about the essential ontological relation between an omnipotent God and the created world that he sustains in existence. Occasionalism can also be regarded as a way of providing a metaphysical foundation for explanations in mechanistic natural philosophy. Occasionalists are arguing that motion must ultimately be grounded in something higher than the passive, inert extension of Cartesian bodies (emptied of the substantial forms of the Scholastics); it needs a causal ground in an active power. But if a body consists in extension alone, motive force cannot be an inherent property of bodies. Occasionalists thus identify force with the will of God. In this way, they are simply drawing out the implications of Descartes’s own metaphysics of matter and motion. See also CORDEMOY , GEULINCX , LEIBNIZ , MALEBRANCH. S.N.