Reply Obj. 1:  In this passage Augustine calls by the name of “thing,” that which is a thing simply, viz. substance; for in this sense the act of sin is not a thing.

Reply Obj. 2:  Not only the act, but also the defect, is reduced to man as its cause, which defect consists in man not being subject to Whom he ought to be, although he does not intend this principally.  Wherefore man is the cause of the sin:  while God is the cause of the act, in such a way, that nowise is He the cause of the defect accompanying the act, so that He is not the cause of the sin.

Reply Obj. 3:  As stated above (Q. 72, A. 1), acts and habits do not take their species from the privation itself, wherein consists the nature of evil, but from some object, to which that privation is united:  and so this defect which consists in not being from God, belongs to the species of the act consequently, and not as a specific difference. ________________________

THIRD ARTICLE [I-II, Q. 79, Art. 3]

Whether God Is the Cause of Spiritual Blindness and Hardness of
Heart?

Objection 1:  It would seem that God is not the cause of spiritual blindness and hardness of heart.  For Augustine says (Qq. lxxxiii, qu. 3) that God is not the cause of that which makes man worse.  Now man is made worse by spiritual blindness and hardness of heart.  Therefore God is not the cause of spiritual blindness and hardness of heart.

Obj. 2:  Further, Fulgentius says (De Dupl.  Praedest. i, 19):  “God does not punish what He causes.”  Now God punishes the hardened heart, according to Ecclus. 3:27:  “A hard heart shall fear evil at the last.”  Therefore God is not the cause of hardness of heart.

Obj. 3:  Further, the same effect is not put down to contrary causes.  But the cause of spiritual blindness is said to be the malice of man, according to Wis. 2:21:  “For their own malice blinded them,” and again, according to 2 Cor. 4:4:  “The god of this world hath blinded the minds of unbelievers”:  which causes seem to be opposed to God.  Therefore God is not the cause of spiritual blindness and hardness of heart.

On the contrary, It is written (Isa. 6:10):  “Blind the heart of this people, and make their ears heavy,” and Rom. 9:18:  “He hath mercy on whom He will, and whom He will He hardeneth.”

I answer that, Spiritual blindness and hardness of heart imply two things.  One is the movement of the human mind in cleaving to evil, and turning away from the Divine light; and as regards this, God is not the cause of spiritual blindness and hardness of heart, just as He is not the cause of sin.  The other thing is the withdrawal of grace, the result of which is that the mind is not enlightened by God to see aright, and man’s heart is not softened to live aright; and as regards this God is the cause of spiritual blindness and hardness of heart.