occasionalism, metaphysical doctrine that denies that finite things have any active power and asserts that God is the only cause, whereas physical events and mental states are only occasions for God's action. Muslim theologians in the 8th cent. developed a version of occasionalism as an alternative to Aristotelian theories of causality. Occasionalism gained currency in the West in the 17th cent., when Arnold Geulincx and Nicolas Malebranche developed theories to resolve the problem of interaction in general, and of that between mind (immaterial) and body (material) in particular, which was posed by the dualism of René Descartes.

Type of mind-body dualism that maintains that apparent interactions between mental and physical events are in reality the result of God's constant causal action. Starting from Descartes's mind-body dualism, the occasionalists, whose most prominent exponents were Nicolas de Malebranche and Arnold Geulincx, drew the conclusions that there can be no interaction between mind and body, and that all causality is immanent, within one order or the other, and any appearance of mind affecting body or of body affecting mind must be explained as the result of a special intervention by God, who, on the occasion of changes in one substance, produces corresponding changes in the other.

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