Summa summae S. Thomae sive compendium theologiae

I say: Invincible ignorance concerning the existence of God as natural author cannot be given.

It is proved first from the Scriptures. Those who have been ignorant of God are called indiscriminately inexcusable, Rom. I, 20. Therefore they were ignorant vincibly and culpably. Moreover it is said, Ps. LXXVIII, 6: Pour out thy wrath upon the nations that have not known thee, and upon the kingdoms that have not invoked thy name. But the Prophet, inspired by God, would not say this unless their ignorance were vincible and culpable. Therefore.

It is proved secondly from the Fathers. Augustine says, In Ps. LXXIV: “God everywhere hidden, everywhere manifest, whom it is permitted to none to know as He is, and whom no one is permitted to be ignorant of.” Chrysostom, on these words: The heavens declare the glory of God, says, Hom. IX ad pop. Antioch.: “The Scythian, and the barbarian, and the Jew, and the Egyptian, and every man walking upon the earth, hears this voice... Upon this book alike both the unlettered and the wise will be able to look.” Gregory the Great, book XXVII of the Moral., c. 9: “Every man, by the very fact that he has been made rational, ought from reason to gather that He who made him is God.”

It is proved by the third argument, by which also sufficient satisfaction is made to the foundation of the contrary opinion:

[Our first conclusion is evidently inferred from the principles set forth above. For, on the one hand, creatures, both as regards their motion and disposition, and as regards their subordination in causality, and as regards their contingency, and finally as regards their diverse grades of perfection, are daily set before the eyes of man; and, insofar as they are effects dependent on a cause, they are of themselves suited to lead to the cognition of the existence of a first unmoved mover, of a first efficient cause, of a supreme intelligence ordering all things to an end, of a necessary and most perfect being: to all which is added consciousness of our temporary existence and of the imperfect nature of our intelligence. — On the other hand, there is the natural desire of knowing the cause which is apprehended confusedly by our mind as soon as in the cognition of an effect; and for the fulfilling of this desire, reason, by the natural power of reasoning in which it rejoices, is naturally fitted, as was said in the third principle set forth above. Therefore, if man, using reason, does not know the creator from creatures, it must deservedly be affirmed that he does not do what is in him, and that by a base and culpable sloth he certainly neglects to apply natural reason to the inquiry into the primary truth from which the rest flow, and which, if cut off, no other can stand. Invincible ignorance, therefore, is excluded by that very fact from him, according to the definition given. Elsewhere]

Secondly. Although the existence of God is not per se known with respect to us, as we said above, but is demonstrable from creatures, nevertheless this demonstration is so easy, so obvious, that there is no one of sound mind, however rustic or barbarous, who is not capable of it, or at least to whom, from the inspection of the world or of himself, some suspicion or conjectural opinion of some supreme numen or ruler does not occur, as is clear from the Scriptures and Fathers cited; once this has been set before him, he is bound to inquire who He is; and if he neglects this, he is ignorant in a vincible way. Therefore.

Add that, if a man could be invincibly ignorant of God, however wicked he might be, he would commit no mortal sin. For mortal sin is an offense against God; but one who is invincibly not known cannot be offended.

[Here the proposition condemned by Alexander VIII must be noted: « Philosophical or moral sin is a human act at variance with rational nature and right reason; theological and mortal sin, however, is a free transgression of the divine law. Philosophical sin, however grave it may be, in one who either is ignorant of God or does not actually think of God, is a grave sin, but not an offense against God nor a mortal sin dissolving the friendship of God, nor worthy of eternal punishment. » — This proposition, which Arnaldus had fabricated and, as was his custom, attributed to his adversaries, was noted as scandalous, rash, offensive to pious ears, and erroneous.]