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.
Objection 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.
Objection 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 (Is. 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.
Now we must consider that God is the universal cause of the enlightening of souls, according to Jn. 1:9: "That was the true light which enlighteneth every man that cometh into this world," even as the sun is the universal cause of the enlightening of bodies, though not in the same way; for the sun enlightens by necessity of nature, whereas God works freely, through the order of His wisdom. Now although the sun, so far as it is concerned, enlightens all bodies, yet if it be encountered by an obstacle in a body, it leaves it in darkness, as happens to a house whose window-shutters are closed, although the sun is in no way the cause of the house being darkened, since it does not act of its own accord in failing to light up the interior of the house; and the cause of this is the person who closed the shutters. On the other hand, God, of His own accord, withholds His grace from those in whom He finds an obstacle: so that the cause of grace being withheld is not only the man who raises an obstacle to grace; but God, Who, of His own accord, withholds His grace. In this way, God is the cause of spiritual blindness, deafness of ear, and hardness of heart.
These differ from one another in respect of the effects of grace, which both perfects the intellect by the gift of wisdom, and softens the affections by the fire of charity. And since two of the senses excel in rendering service to the intellect, viz. sight and hearing, of which the former assists "discovery," and the latter, "teaching," hence it is that spiritual "blindness" corresponds to sight, "heaviness of the ears" to hearing, and "hardness of heart" to the affections.
Reply to Objection 1: Blindness and hardheartedness, as regards the withholding of grace, are punishments, and therefore, in this respect, they make man no worse. It is because he is already worsened by sin that he incurs them, even as other punishments.
Reply to Objection 2: This argument considers hardheartedness in so far as it is a sin.
Reply to Objection 3: Malice is the demeritorious cause of blindness, just as sin is the cause of punishment: and in this way too, the devil is said to blind, in so far as he induces man to sin.
I–II · Q. 79, Art. 4: Whether blindness and hardness of heart are directed to the salvation of those who are blinded and hardened?
Whether blindness and hardness of heart are directed to the salvation of those who are blinded and hardened?
Objection 1: It would seem that blindness and hardness of heart are always directed to the salvation of those who are blinded and hardened. For Augustine says (Enchiridion xi) that "as God is supremely good, He would nowise allow evil to be done, unless He could draw some good from every evil." Much more, therefore, does He direct to some good, the evil of which He Himself is the cause. Now God is the cause of blindness and hardness of heart, as stated above (A 3). Therefore they are directed to the salvation of those who are blinded and hardened.
Objection 2: Further, it is written (Wis. 1:13) that "God hath no pleasure in the destruction of the ungodly [*Vulg.: 'God made not death, neither hath He pleasure in the destruction of the living.']." Now He would seem to take pleasure in their destruction, if He did not turn their blindness to their profit: just as a physician would seem to take pleasure in torturing the invalid, if he did not intend to heal the invalid when he prescribes a bitter medicine for him. Therefore God turns blindness to the profit of those who are blinded.
Objection 3: Further, "God is not a respecter of persons" (Acts 10:34). Now He directs the blinding of some, to their salvation, as in the case of some of the Jews, who were blinded so as not to believe in Christ, and, through not believing, to slay Him, and afterwards were seized with compunction, and converted, as related by Augustine (De Quaest. Evang. iii). Therefore God turns all blindness to the spiritual welfare of those who are blinded.
Objection 4: On the other hand, according to Rom. 3:8, evil should not be done, that good may ensue. Now blindness is an evil. Therefore God does not blind some for the sake of their welfare.
I answer that, Blindness is a kind of preamble to sin. Now sin has a twofold relation---to one thing directly, viz. to the sinner's damnation---to another, by reason of God's mercy or providence, viz. that the sinner may be healed, in so far as God permits some to fall into sin, that by acknowledging their sin, they may be humbled and converted, as Augustine states (De Nat. et Grat. xxii). Therefore blindness, of its very nature, is directed to the damnation of those who are blinded; for which reason it is accounted an effect of reprobation. But, through God's mercy, temporary blindness is directed medicinally to the spiritual welfare of those who are blinded. This mercy, however, is not vouchsafed to all those who are blinded, but only to the predestinated, to whom "all things work together unto good" (Rom. 8:28). Therefore as regards some, blindness is directed to their healing; but as regards others, to their damnation; as Augustine says (De Quaest. Evang. iii).
Reply to Objection 1: Every evil that God does, or permits to be done, is directed to some good; yet not always to the good of those in whom the evil is, but sometimes to the good of others, or of the whole universe: thus He directs the sin of tyrants to the good of the martyrs, and the punishment of the lost to the glory of His justice.
Reply to Objection 2: God does not take pleasure in the loss of man, as regards the loss itself, but by reason of His justice, or of the good that ensues from the loss.
Reply to Objection 3: That God directs the blindness of some to their spiritual welfare, is due to His mercy; but that the blindness of others is directed to their loss is due to His justice: and that He vouchsafes His mercy to some, and not to all, does not make God a respecter of persons, as explained in the FP, Q 23, A 5, ad 3.
Reply to Objection 4: Evil of fault must not be done, that good may ensue; but evil of punishment must be inflicted for the sake of good.