Thomas Aquinas John Webster on Why God is Not Self-Caused

“Tell me how I got here again . . .”

When pressed, the concept of [God as causa sui] soon shows itself incoherent and dogmatically precarious. At a purely formal level, it seems to suggest that God in some way precedes himself as his own cause . . . The dogmatic difficulties are equally serious. Talk of God as his own cause cannot easily cohere with teaching about divine eternity or immutability, since it appears to introduce an actualist concept of God’s ‘coming-to-be’ as the result of some causal process. Further, it imperils divine simplicity, introducing distinctions between cause and that which is caused, or between potentiality and act, which, by attributing potentiality to God, undermine the all-important identity of essence and existence in God . . . By suggesting that God produces himself, it seems to require the possibility of God’s non-existence as a kind of background to his being. In effect, a God who is his own cause lacks an integral element of perfection. If the concept of causa sui is to be used, therefore, the notion of cause must first be stripped of any associations with ‘becoming’ or ‘coming-into-existence’ – of anything that might corrode the eternal fullness of God’s being.

John Webster, ‘Life in and of Himself’, in God without Measure: Working Papers in Christian Theology. Volume i: God and the Works of God (London: Bloomsbury T&T Clark, 2016), pp. 22–23