Summa contra Gentiles3.162 Chapter CLXII. That God is not the cause of any man sinning

Although God converts not certain sinners to Himself, but leaves them in their sins, as they deserve to be, yet He does not lead them to sin.

For man sins through wandering away from Him who is his last end, as we have already shown. Now, as every agent acts for an end proper and proportionate to it, it is impossible that God, by His own action, turn anyone away from his last end, which is God. Therefore it is impossible that God make any man sin.

Again. Good cannot be a cause of evil. Now sin is man’s evil: for it is contrary to man’s proper good, which is to live according to reason. Therefore God cannot be the cause of a man sinning.

Further. All human wisdom and goodness flow from the divine wisdom and goodness, and are a kind of likeness thereof. Now it is incompatible with human wisdom and goodness, to make a man sin. Much more therefore is it incompatible with divine wisdom.

Moreover. All sin arises from a fault in the proximate agent, and not from the influence of the first agent: thus the fault of limping is due to a defect in the tibia, and not to the motive power; to which, however, is due whatever there is of the perfection of movement in limping. Now, the proximate agent in human sin is the will. Therefore the defect of sin arises from man’s will and not from God, who is the first agent: although whatever pertains to the perfection of action in the sinful act is due to Him.

Hence it is said (Ecclus. xv. 12): Say not: He hath caused me to err: for He hath no need of wicked men: and further on (verse 21): He hath commanded no man to do wickedly, and He hath given to no man license to sin. Also (James i. 13): Let no man, when he is tempted, say that he is tempted by God: for God is not a tempter of evils.

There are, however, a few passages in Scripture which would seem to indicate chat, to some, God is the cause of their sinning. For it is said (Exod. x. 1): I have hardened Pharaoh’s heart and the heart of his servants: and (Isa. vi. 10): Blind the heart of this people, make their ears heavy: lest they see with their eyes... and be converted, and I heal them: and (ibid, lxiii. 17): Thou hast made us to err from Thy ways:... thou hast hardened our heart, that we should not fear Thee. Again it is said (Rom. i. 28): God delivered them up to a reprobate sense, to do those things which are not convenient. All these passages are to be understood in the sense that God does not assist some to avoid sin, whereas He does assist others.

This assistance is not only the infusion of grace, but also external protection whereby occasions of sin are warded off by divine providence, and incentives to sin restrained. God also assists man against sin by the natural light of reason and the other natural goods which He bestows on man. Hence when He withdraws these aids from some men, as their actions merit, according to the demands of His justice, He is said to harden their hearts or blind their eyes, or deal with them in some other way as described in the passages above quoted.