Theology surpasses the other sciences in certainty, both in the object and in the habit of faith

Hence it comes about that theology surpasses all the remaining sciences in certainty. For those rest on human reason, which can be deceived and is liable to error. But theology reclines upon the truth of God, who can neither be deceived nor deceive. Many indeed waver about theological truths, and to them the principles and conclusions of theology seem less certain than the things handed down in the human sciences. But that does not hinder them from being in themselves most certain — just as the sun does not cease to be most splendid, though the blind and the bleary-eyed either do not perceive its light at all, or perceive it only obscurely.

But here it must be noticed that when we set theology as more certain than the other sciences, we do not so understand it as if that certainty were only on the side of the object. For the things which God has revealed are not only most certain in themselves, but can also be known more certainly through the habit of faith and of theology than any truths known through the light of reason alone. So that one who is strengthened in faith and in the science of divine things is more certain, and more persuaded, concerning the divine truths than he is concerning any other truth. And thus the habit of faith and of theology, in itself and from its own species, excels in certainty the habit of the merely natural sciences — although not all participate that habit equally, and it is firmer in one person and less firm in another.