The Incoherence of Causal Necessity

The philosophers hold that fire necessarily burns cotton when they come into contact — that the causal connection is intrinsic to the natures of fire and cotton. Al-Ghazali denies this. What we observe is constant conjunction, not necessity: fire has always in the past preceded burning, but there is no logical or metaphysical necessity that it must do so. God could, and in miraculous cases does, preserve the cotton from burning while fire touches it.

Al-Ghazali's positive doctrine is that the apparent regularities of nature are the product of God's customary action (sunnat Allah) — God's habit of creating effects whenever their apparent causes occur — rather than of any causal power inherent in created things. This is not classical occasionalism (which denies all secondary causation), but it insists that created things possess no causal power of their own without divine permission.

This argument has enormous consequences. It preserves the logical possibility of miracles: if causation is not necessary, then God can interrupt the customary sequence without logical contradiction. It also challenges the philosophical programme of explaining the world through rational necessity: if the basic fabric of causation is God's will, then natural science describes God's habits, not necessary laws.

The attack on causal necessity appears in the 17th discussion of The Incoherence of the Philosophers. Averroes replies in The Incoherence of the Incoherence.