Objection 2: Further, sin is opposed to virtue as illness to health, as stated above (Q[71], A[1], ad 3). Now, man, by force of his nature, can rise from illness to health, without the external help of medicine, since there still remains in him the principle of life, from which the natural operation proceeds. Hence it seems that, with equal reason, man may be restored by himself, and return from the state of sin to the state of justice without the help of external grace.
Objection 3: Further, every natural thing can return by itself to the act befitting its nature, as hot water returns by itself to its natural coldness, and a stone cast upwards returns by itself to its natural movement. Now a sin is an act against nature, as is clear from Damascene (De Fide Orth. ii, 30). Hence it seems that man by himself can return from sin to the state of justice.
On the contrary, The Apostle says ( Gal. 2:21 ; Cf. Gal. 3:21 ): "For if there had been a law given which could give life---then Christ died in vain," i.e. to no purpose. Hence with equal reason, if man has a nature, whereby he can he justified, "Christ died in vain," i.e. to no purpose. But this cannot fittingly be said. Therefore by himself he cannot be justified, i.e. he cannot return from a state of sin to a state of justice.
I answer that, Man by himself can no wise rise from sin without the help of grace. For since sin is transient as to the act and abiding in its guilt, as stated above (Q[87], A[6]), to rise from sin is not the same as to cease the act of sin; but to rise from sin means that man has restored to him what he lost by sinning. Now man incurs a triple loss by sinning, as was clearly shown above (Q[85], A[1]; Q[86], A[1]; Q[87], A[1]), viz. stain, corruption of natural good, and debt of punishment. He incurs a stain, inasmuch as he forfeits the lustre of grace through the deformity of sin. Natural good is corrupted, inasmuch as man's nature is disordered by man's will not being subject to God's; and this order being overthrown, the consequence is that the whole nature of sinful man remains disordered. Lastly, there is the debt of punishment, inasmuch as by sinning man deserves everlasting damnation.
Now it is manifest that none of these three can be restored except by God. For since the lustre of grace springs from the shedding of Divine light, this lustre cannot be brought back, except God sheds His light anew: hence a habitual gift is necessary, and this is the light of grace. Likewise, the order of nature can only be restored, i.e. man's will can only be subject to God when God draws man's will to Himself, as stated above (A[6]). So, too, the guilt of eternal punishment can be remitted by God alone, against Whom the offense was committed and Who is man's Judge. And thus in order that man rise from sin there is required the help of grace, both as regards a habitual gift, and as regards the internal motion of God.
Reply to Objection 1: To man is bidden that which pertains to the act of free-will, as this act is required in order that man should rise from sin. Hence when it is said, "Arise, and Christ shall enlighten thee," we are not to think that the complete rising from sin precedes the enlightenment of grace; but that when man by his free-will, moved by God, strives to rise from sin, he receives the light of justifying grace.
Reply to Objection 2: The natural reason is not the sufficient principle of the health that is in man by justifying grace. This principle is grace which is taken away by sin. Hence man cannot be restored by himself; but he requires the light of grace to be poured upon him anew, as if the soul were infused into a dead body for its resurrection.
Reply to Objection 3: When nature is perfect, it can be restored by itself to its befitting and proportionate condition; but without exterior help it cannot be restored to what surpasses its measure. And thus human nature undone by reason of the act of sin, remains no longer perfect, but corrupted, as stated above (Q[85]); nor can it be restored, by itself, to its connatural good, much less to the supernatural good of justice.
Whether man without grace can avoid sin?
Objection 1: It would seem that without grace man can avoid sin. Because "no one sins in what he cannot avoid," as Augustine says (De Duab. Anim. x, xi; De Libero Arbit. iii, 18). Hence if a man in mortal sin cannot avoid sin, it would seem that in sinning he does not sin, which is impossible.
Objection 2: Further, men are corrected that they may not sin. If therefore a man in mortal sin cannot avoid sin, correction would seem to be given to no purpose; which is absurd.
Objection 3: Further, it is written ( Ecclus. 15:18 ): "Before man is life and death, good and evil; that which he shall choose shall be given him." But by sinning no one ceases to be a man. Hence it is still in his power to choose good or evil; and thus man can avoid sin without grace.
On the contrary, Augustine says (De Perfect Just. xxi): "Whoever denies that we ought to say the prayer 'Lead us not into temptation' (and they deny it who maintain that the help of God's grace is not necessary to man for salvation, but that the gift of the law is enough for the human will) ought without doubt to be removed beyond all hearing, and to be anathematized by the tongues of all."
I answer that, We may speak of man in two ways: first, in the state of perfect nature; secondly, in the state of corrupted nature. Now in the state of perfect nature, man, without habitual grace, could avoid sinning either mortally or venially; since to sin is nothing else than to stray from what is according to our nature---and in the state of perfect nature man could avoid this. Nevertheless he could not have done it without God's help to uphold him in good, since if this had been withdrawn, even his nature would have fallen back into nothingness.
But in the state of corrupt nature man needs grace to heal his nature in order that he may entirely abstain from sin. And in the present life this healing is wrought in the mind---the carnal appetite being not yet restored. Hence the Apostle ( Rom. 7:25 ) says in the person of one who is restored: "I myself, with the mind, serve the law of God, but with the flesh, the law of sin." And in this state man can abstain from all mortal sin, which takes its stand in his reason, as stated above (Q[74], A[5]); but man cannot abstain from all venial sin on account of the corruption of his lower appetite of sensuality. For man can, indeed, repress each of its movements (and hence they are sinful and voluntary), but not all, because whilst he is resisting one, another may arise, and also because the reason is always alert to avoid these movements, as was said above (Q[74], A[3], ad 2).
So, too, before man's reason, wherein is mortal sin, is restored by justifying grace, he can avoid each mortal sin, and for a time, since it is not necessary that he should be always actually sinning. But it cannot be that he remains for a long time without mortal sin. Hence Gregory says (Super Ezech. Hom. xi) that " a sin not at once taken away by repentance, by its weight drags us down to other sins": and this because, as the lower appetite ought to be subject to the reason, so should the reason be subject to God, and should place in Him the end of its will. Now it is by the end that all human acts ought to be regulated, even as it is by the judgment of the reason that the movements of the lower appetite should be regulated. And thus, even as inordinate movements of the sensitive appetite cannot help occurring since the lower appetite is not subject to reason, so likewise, since man's reason is not entirely subject to God, the consequence is that many disorders occur in the reason. For when man's heart is not so fixed on God as to be unwilling to be parted from Him for the sake of finding any good or avoiding any evil, many things happen for the achieving or avoiding of which a man strays from God and breaks His commandments, and thus sins mortally: especially since, when surprised, a man acts according to his preconceived end and his pre-existing habits, as the Philosopher says (Ethic. iii); although with premeditation of his reason a man may do something outside the order of his preconceived end and the inclination of his habit. But because a man cannot always have this premeditation, it cannot help occurring that he acts in accordance with his will turned aside from God, unless, by grace, he is quickly brought back to the due order.
Reply to Objection 1: Man can avoid each but every act of sin, except by grace, as stated above. Nevertheless, since it is by his own shortcoming that he does not prepare himself to have grace, the fact that he cannot avoid sin without grace does not excuse him from sin.
Reply to Objection 2: Correction is useful "in order that out of the sorrow of correction may spring the wish to be regenerate; if indeed he who is corrected is a son of promise, in such sort that whilst the noise of correction is outwardly resounding and punishing, God by hidden inspirations is inwardly causing to will," as Augustine says (De Corr. et Gratia vi). Correction is therefore necessary, from the fact that man's will is required in order to abstain from sin; yet it is not sufficient without God's help. Hence it is written ( Eccles. 7:14 ): "Consider the works of God that no man can correct whom He hath despised."
Reply to Objection 3: As Augustine says (Hypognosticon iii [*Among the spurious works of St. Augustine]), this saying is to be understood of man in the state of perfect nature, when as yet he was not a slave of sin. Hence he was able to sin and not to sin. Now, too, whatever a man wills, is given to him; but his willing good, he has by God's assistance.
Whether one who has already obtained grace, can, of himself and without further help of grace, do good and avoid sin?
Objection 1: It would seem that whoever has already obtained grace, can by himself and without further help of grace, do good and avoid sin. For a thing is useless or imperfect, if it does not fulfil what it was given for. Now grace is given to us that we may do good and keep from sin. Hence if with grace man cannot do this, it seems that grace is either useless or imperfect.
Objection 2: Further, by grace the Holy Spirit dwells in us, according to 1 Cor. 3:16 : "Know you not that you are the temple of God, and that the Spirit of God dwelleth in you?" Now since the Spirit of God is omnipotent, He is sufficient to ensure our doing good and to keep us from sin. Hence a man who has obtained grace can do the above two things without any further assistance of grace.
Objection 3: Further, if a man who has obtained grace needs further aid of grace in order to live righteously and to keep free from sin, with equal reason, will he need yet another grace, even though he has obtained this first help of grace. Therefore we must go on to infinity; which is impossible. Hence whoever is in grace needs no further help of grace in order to do righteously and to keep free from sin.
On the contrary, Augustine says (De Natura et Gratia xxvi) that "as the eye of the body though most healthy cannot see unless it is helped by the brightness of light, so, neither can a man, even if he is most righteous, live righteously unless he be helped by the eternal light of justice." But justification is by grace, according to Rom. 3:24 : "Being justified freely by His grace." Hence even a man who already possesses grace needs a further assistance of grace in order to live righteously.
I answer that, As stated above (A[5]), in order to live righteously a man needs a twofold help of God---first, a habitual gift whereby corrupted human nature is healed, and after being healed is lifted up so as to work deeds meritoriously of everlasting life, which exceed the capability of nature. Secondly, man needs the help of grace in order to be moved by God to act.