Reply to Objection 1: Mortal sin both turns away from God and turns to a created good. But, as stated in the FS, Q[71], A[6], the turning away from God is as its form while the turning to created good is as its matter. Now if the formal element of anything be removed, the species is taken away: thus, if you take away rational, you take away the human species. Consequently mortal sin is said to be pardoned from the very fact that, by means of grace, the aversion of the mind from God is taken away together with the debt of eternal punishment: and yet the material element remains, viz. the inordinate turning to a created good, for which a debt of temporal punishment is due.
Reply to Objection 2: As stated in the FS, Q[109], AA[7],8; FS, Q[111], A[2], it belongs to grace to operate in man by justifying him from sin, and to co-operate with man that his work may be rightly done. Consequently the forgiveness of guilt and of the debt of eternal punishment belongs to operating grace, while the remission of the debt of temporal punishment belongs to co-operating grace, in so far as man, by bearing punishment patiently with the help of Divine grace, is released also from the debt of temporal punishment. Consequently just as the effect of operating grace precedes the effect of co-operating grace, so too, the remission of guilt and of eternal punishment precedes the complete release from temporal punishment, since both are from grace, but the former, from grace alone, the latter, from grace and free-will.
Reply to Objection 3: Christ's Passion is of itself sufficient to remove all debt of punishment, not only eternal, but also temporal; and man is released from the debt of punishment according to the measure of his share in the power of Christ's Passion. Now in Baptism man shares the Power of Christ's Passion fully, since by water and the Spirit of Christ, he dies with Him to sin, and is born again in Him to a new life, so that, in Baptism, man receives the remission of all debt of punishment. In Penance, on the other hand, man shares in the power of Christ's Passion according to the measure of his own acts, which are the matter of Penance, as water is of Baptism, as stated above (Q[84], AA[1],3). Wherefore the entire debt of punishment is not remitted at once after the first act of Penance, by which act the guilt is remitted, but only when all the acts of Penance have been completed.
Whether the remnants of sin are removed when a mortal sin is forgiven?
Objection 1: It would seem that all the remnants of sin are removed when a mortal sin is forgiven. For Augustine says in De Poenitentia [*De vera et falsa Poenitentia, the authorship of which is unknown]: "Our Lord never healed anyone without delivering him wholly; for He wholly healed the man on the Sabbath, since He delivered his body from all disease, and his soul from all taint." Now the remnants of sin belong to the disease of sin. Therefore it does not seem possible for any remnants of sin to remain when the guilt has been pardoned.
Objection 2: Further, according to Dionysius (Div. Nom. iv), "good is more efficacious than evil, since evil does not act save in virtue of some good." Now, by sinning, man incurs the taint of sin all at once. Much more, therefore, by repenting, is he delivered also from all remnants of sin.
Objection 3: Further, God's work is more efficacious than man's. Now by the exercise of good human works the remnants of contrary sins are removed. Much more, therefore, are they taken away by the remission of guilt, which is a work of God.
On the contrary, We read ( Mk. 8 ) that the blind man whom our Lord enlightened, was restored first of all to imperfect sight, wherefore he said ( Mk. 8:24 ): "I see men, as it were trees, walking"; and afterwards he was restored perfectly, "so that he saw all things clearly." Now the enlightenment of the blind man signifies the delivery of the sinner. Therefore after the first remission of sin, whereby the sinner is restored to spiritual sight, there still remain in him some remnants of his past sin.
I answer that, Mortal sin, in so far as it turns inordinately to a mutable good, produces in the soul a certain disposition, or even a habit, if the acts be repeated frequently. Now it has been said above (A[4]) that the guilt of mortal sin is pardoned through grace removing the aversion of the mind from God. Nevertheless when that which is on the part of the aversion has been taken away by grace, that which is on the part of the inordinate turning to a mutable good can remain, since this may happen to be without the other, as stated above (A[4]). Consequently, there is no reason why, after the guilt has been forgiven, the dispositions caused by preceding acts should not remain, which are called the remnants of sin. Yet they remain weakened and diminished, so as not to domineer over man, and they are after the manner of dispositions rather than of habits, like the "fomes" which remains after Baptism.
Reply to Objection 1: God heals the whole man perfectly; but sometimes suddenly, as Peter's mother-in-law was restored at once to perfect health, so that "rising she ministered to them" ( Lk. 4:39 ), and sometimes by degrees, as we said above (Q[44], A[3], ad 2) about the blind man who was restored to sight ( Mat. 8 ). And so too, He sometimes turns the heart of man with such power, that it receives at once perfect spiritual health, not only the guilt being pardoned, but all remnants of sin being removed as was the case with Magdalen ( Lk. 7 ); whereas at other times He sometimes first pardons the guilt by operating grace, and afterwards, by co-operating grace, removes the remnants of sin by degrees.
Reply to Objection 2: Sin too, sometimes induces at once a weak disposition, such as is the result of one act, and sometimes a stronger disposition, the result of many acts.
Reply to Objection 3: One human act does not remove all the remnants of sin, because, as stated in the Predicaments (Categor. viii) "a vicious man by doing good works will make but little progress so as to be any better, but if he continue in good practice, he will end in being good as to acquired virtue." But God's grace does this much more effectively, whether by one or by several acts.
Whether the forgiveness of guilt is an effect of Penance?
Objection 1: It would seem that the forgiveness of guilt is not an effect of penance as a virtue. For penance is said to be a virtue, in so far as it is a principle of a human action. But human action does nothing towards the remission of guilt, since this is an effect of operating grace. Therefore the forgiveness of guilt is not an effect of penance as a virtue.
Objection 2: Further, certain other virtues are more excellent than penance. But the forgiveness of sin is not said to be the effect of any other virtue. Neither, therefore, is it the effect of penance as a virtue.
Objection 3: Further, there is no forgiveness of sin except through the power of Christ's Passion, according to Heb. 9:22 : "Without shedding of blood there is no remission." Now Penance, as a sacrament, produces its effect through the power of Christ's Passion, even as the other sacraments do, as was shown above (Q[62], AA[4],5). Therefore the forgiveness of sin is the effect of Penance, not as a virtue, but as a sacrament.
On the contrary, Properly speaking, the cause of a thing is that without which it cannot be, since every defect depends on its cause. Now forgiveness of sin can come from God without the sacrament of Penance, but not without the virtue of penance, as stated above (Q[84], A[5], ad 3; Q[85], A[2]); so that, even before the sacraments of the New Law were instituted, God pardoned the sins of the penitent. Therefore the forgiveness of sin is chiefly the effect of penance as a virtue.
I answer that, Penance is a virtue in so far as it is a principle of certain human acts. Now the human acts, which are performed by the sinner, are the material element in the sacrament of Penance. Moreover every sacrament produces its effect, in virtue not only of its form, but also of its matter. because both these together make the one sacrament, as stated above (Q[60], A[6], ad 2, A[7]). Hence in Baptism forgiveness of sin is effected, in virtue not only of the form (but also of the matter, viz. water, albeit chiefly in virtue of the form) [*The words in brackets are omitted in the Leonine edition] from which the water receives its power---and, similarly, the forgiveness of sin is the effect of Penance, chiefly by the power of the keys, which is vested in the ministers, who furnish the formal part of the sacrament, as stated above (Q[84], A[3]), and secondarily by the instrumentality of those acts of the penitent which pertain to the virtue of penance, but only in so far as such acts are, in some way, subordinate to the keys of the Church. Accordingly it is evident that the forgiveness of sin is the effect of penance as a virtue, but still more of Penance as a sacrament.
Reply to Objection 1: The effect of operating grace is the justification of the ungodly (as stated in the FS, Q[113]), wherein there is, as was there stated (AA[1],2,3), not only infusion of grace and forgiveness of sin, but also a movement of the free-will towards God, which is an act of faith quickened by charity, and a movement of the free-will against sin, which is the act of penance. Yet these human acts are there as the effects of operating grace, and are produced at the same time as the forgiveness of sin. Consequently the forgiveness of sin does not take place without an act of the virtue of penance, although it is the effect of operating grace.
Reply to Objection 2: In the justification of the ungodly there is not only an act of penance, but also an act of faith, as stated above (ad 1: FS, Q[113], A[4]). Wherefore the forgiveness of sin is accounted the effect not only of the virtue of penance, but also, and that chiefly, of faith and charity.
Reply to Objection 3: The act of the virtue of penance is subordinate to Christ's Passion both by faith, and by its relation to the keys of the Church; and so, in both ways, it causes the forgiveness of sin, by the power of Christ's Passion.
To the argument advanced in the contrary sense we reply that the act of the virtue of penance is necessary for the forgiveness of sin, through being an inseparable effect of grace, whereby chiefly is sin pardoned, and which produces its effect in all the sacraments. Consequently it only follows that grace is a higher cause of the forgiveness of sin than the sacrament of Penance. Moreover, it must be observed that, under the Old Law and the law of nature, there was a sacrament of Penance after a fashion, as stated above (Q[84], A[7], ad 2).