Occasionalism

Occasionalism is the doctrine that finite created things — bodies and minds — have no genuine causal power of their own. What appears to be the interaction of one body with another, or of mind with body, is really the action of God on the occasion of an apparent interaction. The doctrine had Islamic precursors in al-Ghazali's critique of Aristotelian causation but received its most systematic development in late seventeenth-century French Cartesianism, particularly in the work of Nicolas Malebranche.

Malebranche's occasionalism was driven by two motivations: the felt difficulty of explaining how a Cartesian mental substance could causally affect a physical one, and a robust theological commitment to God's continuous action in creation. The position was attacked by Leibniz, who developed pre-established harmony as an alternative, and by Hume, whose critique of necessary connection in Section VII of the Enquiry was developed in part against the occasionalist tradition.

Al-Ghazali's occasionalism in The Incoherence of the Philosophers (1095) was developed against the Aristotelian-Neoplatonic philosophers (the falasifa) who held that natural causes operate by their own intrinsic powers. Al-Ghazali argued that what looks like the cotton burning when fire is applied to it is really God's direct creation of the burning; the customary correlation between fire and burning is what we observe, but the true cause is divine action. The doctrine preserved God's continuous activity in creation against what al-Ghazali saw as the Aristotelian reduction of God to a remote first cause.

Malebranche's seventeenth-century occasionalism faced the early-modern problem of mind-body interaction directly. Within Cartesian metaphysics, the difficulty of explaining how mental substance affects physical substance was acute, and occasionalism offered a clean solution: there is no genuine causal interaction; God arranges the corresponding sequences. Hume's critique of necessary connection in Section VII of the first Enquiry treated occasionalism extensively, arguing that the appeal to God produces the same problem at a higher level — we no more observe necessary connection between God's will and what follows from it than between any pair of natural events.