Summa contra Gentiles3.118 Chapter CXVIII. That the divine law binds men to the true faith

From this it is clear that the divine law binds men to the true faith.

For just as the beginning of material love is sight exercised through the material eye, so the beginning of spiritual love is the intellectual vision of a spiritual lovable object. Now, the vision of that spiritual lovable object which is God, is impossible to us in the present life except by faith, because it surpasses natural reason, and especially inasmuch as our happiness consists in the enjoyment thereof. Therefore we need to be brought to the true faith by the divine law.

Again. The divine law directs man to perfect subjection to God. Now, as man is subject to God as to His will by loving Him, so is he subject to Him as to his intellect by believing in Him. Not indeed by believing anything false: since God, who is truth, cannot propose anything false to man; wherefore he that believes something false, believes not in God. Therefore the divine law directs man to the true faith.

Also. He who errs about something essential to a thing, knows not that thing: thus if anyone in apprehending an irrational animal were to think it a man, he would not know man. It would be different were he to err about the accidentals of a thing. In composite things, however, he who errs about any of the essential principles, though he know not the thing simply, yet he knows it in some respect; thus if he thinks a man to be an irrational animal, he knows him in respect of his genus. But this cannot apply to simple things, and any error whatever removes all knowledge of the thing. Now, God is supremely simple. Therefore to err about God, is not to know God: thus he who believes that God is a body? knows not God at all, but apprehends something else instead of God. Now, a thing is loved and desired according as it is known. Therefore he that errs about God, can neither love God, nor desire him as his end. Consequently, since the aim of the divine law is to make men love and desire God, that law must needs bind men to a true faith in God.

Moreover. False opinion in matters of intelligence, is like vice opposed to virtue in moral matters: for the true is the good of the intellect, Now, it belongs to the divine law to prohibit vice. Therefore it belongs to it also to proscribe false opinions about God and things divine. Hence it is said (Heb. xi. 6): Without faith it is impossible to please God. Moreover (Exod. xx.) before other commandments are given, a right faith in God is prescribed when it is said: Hear, 0 Israel, the Lord thy God is one.

Hereby is refuted the error of those who maintained that it matters not for man’s salvation with what faith he serves God.