Providence is not occasional divine intervention into an otherwise autonomous natural order. For Aquinas, God's governance is continuous and all-encompassing: every natural event, every free human action, every apparent accident falls within the scope of divine ordering. This is not determinism in any mechanical sense; it is the claim that the universe has a rational author who directs it toward ends that reason can partially discern and that exceed reason's full comprehension.
A crucial feature of Aquinas's account is his insistence on the integrity of secondary causation. God does not govern the world by bypassing natural causes but through them. Fire burns, plants grow, humans reason and choose — and in doing so, they are themselves causes of their effects. The dignity of creaturely causation is preserved: to deny secondary causes would be to diminish the perfection of creation by making creatures mere instruments rather than real agents. Providence governs through the natures God has given things, not despite them.
Aquinas acknowledges that providence must account for the existence of evil. His answer is that God permits natural and moral evil insofar as a greater good follows from it — not that particular evils are themselves good, but that the order of the whole, including the permission of evil, serves an end surpassing what any finite perspective can grasp. The martyrs suffer; sinners misuse freedom; creatures decay. Yet the overall ordering of things toward their highest ends, including the ordering of human freedom toward a beatitude that only God can give, constitutes a governance that is genuinely wise.
Book III of the Summa Contra Gentiles is devoted to divine providence, covering God's governance of intellectual creatures, evil, fate, prayer, miracles, and the ordering of rational beings toward their ultimate end.
