"God does not act through an intervening action which is understood as proceeding from God and terminating in the creature, but his action is his substance and whatever is in him is wholly outside the genus of created existence by which the creature is related to God."
Thomas Aquinas, Quaestiones disputatae de potentia 7.10.Resp., trans. Ralph McInerny (Thomas Aquinas: selected writings, trans. & ed. Ralph McInerny (London: Penguin books, 1998), 337-338).