Summa Th. I-II EN Qu.87 a.4

Whether sin incurs a debt of punishment infinite in quantity?

Objection: 1. It would seem that sin incurs a debt of punishment infinite in quantity. For it is written (Jr 10,24): "Correct me, O Lord, but yet with judgment: and not in Thy fury, lest Thou bring me to nothing." Now God's anger or fury signifies metaphorically the vengeance of Divine justice: and to be brought to nothing is an infinite punishment, even as to make a thing out of nothing denotes infinite power. Therefore according to God's vengeance, sin is awarded a punishment infinite in quantity.
2. Further, quantity of punishment corresponds to quantity of fault, according to Dt 25,2: "According to the measure of the sin shall the measure also of the stripes be." Now a sin which is committed against God, is infinite: because the gravity of a sin increases according to the greatness of the person sinned against (thus it more grievous sin to strike the sovereign than a private individual), and God's greatness is infinite. Therefore an infinite punishment is due for a sin committed against God.
3. Further, a thing may be infinite in two ways, in duration, and in quantity. Now the punishment is infinite in duration. Therefore it is infinite in quantity also.

On the contrary If this were the case, the punishments of all mortal sins would be equal; because one infinite is not greater than another.
I answer that Punishment is proportionate to sin. Now sin comprises two things. First, there is the turning away from the immutable good, which is infinite, wherefore, in this respect, sin is infinite. Secondly, there is the inordinate turning to mutable good. In this respect sin is finite, both because the mutable good itself is finite, and because the movement of turning towards it is finite, since the acts of a creature cannot be infinite. Accordingly, in so far as sin consists in turning away from something, its corresponding punishment is the "pain of loss," which also is infinite, because it is the loss of the infinite good, i.e. God. But in so far as sin turns inordinately to something, its corresponding punishment is the "pain of sense," which is also finite.

Reply to Objection: 1. It would be inconsistent with Divine justice for the sinner to be brought to nothing absolutely, because this would be incompatible with the perpetuity of punishment that Divine justice requires, as stated above (Article [3]). The expression "to be brought to nothing" is applied to one who is deprived of spiritual goods, according to 1Co 13,2: "If I . . . have not charity, I am nothing."
2. This argument considers sin as turning away from something, for it is thus that man sins against God.
3. Duration of punishment corresponds to duration of fault, not indeed as regards the act, but on the part of the stain, for as long as this remains, the debt of punishment remains. But punishment corresponds to fault in the point of severity. And a fault which is irreparable, is such that, of itself, it lasts for ever; wherefore it incurs an everlasting punishment. But it is not infinite as regards the thing it turns to; wherefore, in this respect, it does not incur punishment of infinite quantity.

Whether every sin incurs a debt of eternal punishment?

Objection: 1. It would seem that every sin incurs a debt of eternal punishment. Because punishment, as stated above (Article [4]), is proportionate to the fault. Now eternal punishment differs infinitely from temporal punishment: whereas no sin, apparently, differs infinitely from another, since every sin is a human act, which cannot be infinite. Since therefore some sins incur a debt of everlasting punishment, as stated above (Article [4]), it seems that no sin incurs a debt of mere temporal punishment.
2. Further, original sin is the least of all sins, wherefore Augustine says (Enchiridion xciii) that "the lightest punishment is incurred by those who are punished for original sin alone." But original sin incurs everlasting punishment, since children who have died in original sin through not being baptized, will never see the kingdom of God, as shown by our Lord's words (Jn 3,3): " Unless a man be born again, he cannot see the kingdom of God." Much more, therefore, will the punishments of all other sins be everlasting.
3. Further, a sin does not deserve greater punishment through being united to another sin; for Divine justice has allotted its punishment to each sin. Now a venial sin deserves eternal punishment if it be united to a mortal sin in a lost soul, because in hell there is no remission of sins. Therefore venial sin by itself deserves eternal punishment. Therefore temporal punishment is not due for any sin.

On the contrary Gregory says (Dial. iv, 39), that certain slighter sins are remitted after this life. Therefore all sins are not punished eternally.
I answer that As stated above (Article [3]), a sin incurs a debt of eternal punishment, in so far as it causes an irreparable disorder in the order of Divine justice, through being contrary to the very principle of that order, viz. the last end. Now it is evident that in some sins there is disorder indeed, but such as not to involve contrariety in respect of the last end, but only in respect of things referable to the end, in so far as one is too much or too little intent on them without prejudicing the order to the last end: as, for instance, when a man is too fond of some temporal thing, yet would not offend God for its sake, by breaking one of His commandments. Consequently such sins do not incur everlasting, but only temporal punishment.

Reply to Objection: 1. Sins do not differ infinitely from one another in respect of their turning towards mutable good, which constitutes the substance of the sinful act; but they do differ infinitely in respect of their turning away from something. Because some sins consist in turning away from the last end, and some in a disorder affecting things referable to the end: and the last end differs infinitely from the things that are referred to it.
2. Original sin incurs everlasting punishment, not on account of its gravity, but by reason of the condition of the subject, viz. a human being deprived of grace, without which there is no remission of sin.
3. The same answer applies to the Third Objection about venial sin. Because eternity of punishment does not correspond to the quantity of the sin, but to its irremissibility, as stated above (Article [3]).

Whether the debt of punishment remains after sin?

Objection: 1. It would seem that there remains no debt of punishment after sin. For if the cause be removed the effect is removed. But sin is the cause of the debt of punishment. Therefore, when the sin is removed, the debt of punishment ceases also.
2. Further, sin is removed by man returning to virtue. Now a virtuous man deserves, not punishment, but reward. Therefore, when sin is removed, the debt of punishment no longer remains.
3. Further, "Punishments are a kind of medicine" (Ethic. ii, 3). But a man is not given medicine after being cured of his disease. Therefore, when sin is removed the debt of punishment does not remain.

On the contrary It is written (2S 12,13-14): "David said to Nathan: I have sinned against the Lord. And Nathan said to David: The Lord also hath taken away thy sin; thou shalt not die. Nevertheless because thou hast given occasion to the enemies of the Lord to blaspheme . . . the child that is born to thee shall die." Therefore a man is punished by God even after his sin is forgiven: and so the debt of punishment remains, when the sin has been removed.
I answer that Two things may be considered in sin: the guilty act, and the consequent stain. Now it is evident that in all actual sins, when the act of sin has ceased, the guilt remains; because the act of sin makes man deserving of punishment, in so far as he transgresses the order of Divine justice, to which he cannot return except he pay some sort of penal compensation, which restores him to the equality of justice; so that, according to the order of Divine justice, he who has been too indulgent to his will, by transgressing God's commandments, suffers, either willingly or unwillingly, something contrary to what he would wish. This restoration of the equality of justice by penal compensation is also to be observed in injuries done to one's fellow men. Consequently it is evident that when the sinful or injurious act has ceased there still remains the debt of punishment.But if we speak of the removal of sin as to the stain, it is evident that the stain of sin cannot be removed from the soul, without the soul being united to God, since it was through being separated from Him that it suffered the loss of its brightness, in which the stain consists, as stated above (Question [86], Article [1]). Now man is united to God by his will. Wherefore the stain of sin cannot be removed from man, unless his will accept the order of Divine justice, that is to say, unless either of his own accord he take upon himself the punishment of his past sin, or bear patiently the punishment which God inflicts on him; and in both ways punishment avails for satisfaction. Now when punishment is satisfactory, it loses somewhat of the nature of punishment: for the nature of punishment is to be against the will; and although satisfactory punishment, absolutely speaking, is against the will, nevertheless in this particular case and for this particular purpose, it is voluntary. Consequently it is voluntary simply, but involuntary in a certain respect, as we have explained when speaking of the voluntary and the involuntary (Question [6], Article [6]). We must, therefore, say that, when the stain of sin has been removed, there may remain a debt of punishment, not indeed of punishment simply, but of satisfactory punishment.

Reply to Objection: 1. Just as after the act of sin has ceased, the stain remains, as stated above (Question [86], Article [2]), so the debt of punishment also can remain. But when the stain has been removed, the debt of punishment does not remain in the same way, as stated.
2. The virtuous man does not deserve punishment simply, but he may deserve it as satisfactory: because his very virtue demands that he should do satisfaction for his offenses against God or man.
3. When the stain is removed, the wound of sin is healed as regards the will. But punishment is still requisite in order that the other powers of the soul be healed, since they were so disordered by the sin committed, so that, to wit, the disorder may be remedied by the contrary of that which caused it. Moreover punishment is requisite in order to restore the equality of justice, and to remove the scandal given to others, so that those who were scandalized at the sin many be edified by the punishment, as may be seen in the example of David quoted above.

Whether every punishment is inflicted for a sin?

Objection: 1. It would seem that not every punishment is inflicted for a sin. For it is written (Jn 9,3 Jn 9,2) about the man born blind: "Neither hath this man sinned, nor his parents . . . that he should be born blind." In like manner we see that many children, those also who have been baptized, suffer grievous punishments, fevers, for instance, diabolical possession, and so forth, and yet there is no sin in them after they have been baptized. Moreover before they are baptized, there is no more sin in them than in the other children who do not suffer such things. Therefore not every punishment is inflicted for a sin.
2. Further, that sinners should thrive and that the innocent should be punished seem to come under the same head. Now each of these is frequently observed in human affairs, for it is written about the wicked (Ps 72,5): "They are not in the labor of men: neither shall they be scourged like other men"; and (Jb 21,7): "[Why then do] the wicked live, are [they] advanced, and strengthened with riches" (?)[*The words in brackets show the readings of the Vulgate]; and (Hab. 1:13): "Why lookest Thou upon the contemptuous [Vulg.: 'them that do unjust things'], and holdest Thy peace, when the wicked man oppresseth [Vulg.: 'devoureth'], the man that is more just than himself?" Therefore not every punishment is inflicted for a sin.
3. Further, it is written of Christ (1P 2,22) that "He did no sin, nor was guile found in His mouth." And yet it is said (1P 2,21) that "He suffered for us." Therefore punishment is not always inflicted by God for sin.

On the contrary It is written (Jb 4,7, seqq.): "Who ever perished innocent? Or when were the just destroyed? On the contrary, I have seen those who work iniquity . . . perishing by the blast of God"; and Augustine writes (Retract. i) that "all punishment is just, and is inflicted for a sin."
I answer that As already stated (Article [6]), punishment can be considered in two ways---simply, and as being satisfactory. A satisfactory punishment is, in a way, voluntary. And since those who differ as to the debt of punishment, may be one in will by the union of love, it happens that one who has not sinned, bears willingly the punishment for another: thus even in human affairs we see men take the debts of another upon themselves. If, however, we speak of punishment simply, in respect of its being something penal, it has always a relation to a sin in the one punished. Sometimes this is a relation to actual sin, as when a man is punished by God or man for a sin committed by him. Sometimes it is a relation to original sin: and this, either principally or consequently---principally, the punishment of original sin is that human nature is left to itself, and deprived of original justice: and consequently, all the penalties which result from this defect in human nature.Nevertheless we must observe that sometimes a thing seems penal, and yet is not so simply. Because punishment is a species of evil, as stated in the FP, Question [48], Article [5]. Now evil is privation of good. And since man's good is manifold, viz. good of the soul, good of the body, and external goods, it happens sometimes that man suffers the loss of a lesser good, that he may profit in a greater good, as when he suffers loss of money for the sake of bodily health, or loss of both of these, for the sake of his soul's health and the glory of God. In such cases the loss is an evil to man, not simply but relatively; wherefore it does not answer to the name of punishment simply, but of medicinal punishment, because a medical man prescribes bitter potions to his patients, that he may restore them to health. And since such like are not punishments properly speaking, they are not referred to sin as their cause, except in a restricted sense: because the very fact that human nature needs a treatment of penal medicines, is due to the corruption of nature which is itself the punishment of original sin. For there was no need, in the state of innocence, for penal exercises in order to make progress in virtue; so that whatever is penal in the exercise of virtue, is reduced to original sin as its cause.

Reply to Objection: 1. Such like defects of those who are born with them, or which children suffer from, are the effects and the punishments of original sin, as stated above (Question [85], Article [5]); and they remain even after baptism, for the cause stated above (Question [85], Article [5], ad 2): and that they are not equally in all, is due to the diversity of nature, which is left to itself, as stated above (Question [85], Article [5], ad 1). Nevertheless, they are directed by Divine providence, to the salvation of men, either of those who suffer, or of others who are admonished by their means---and also to the glory of God.
2. Temporal and bodily goods are indeed goods of man, but they are of small account: whereas spiritual goods are man's chief goods. Consequently it belongs to Divine justice to give spiritual goods to the virtuous, and to award them as much temporal goods or evils, as suffices for virtue: for, as Dionysius says (Div. Nom. viii), "Divine justice does not enfeeble the fortitude of the virtuous man, by material gifts." The very fact that others receive temporal goods, is detrimental to their spiritual good; wherefore the psalm quoted concludes (verse 6): "Therefore pride hath held them fast."
3. Christ bore a satisfactory punishment, not for His, but for our sins.

Whether anyone is punished for another's sin?

Objection: 1. It would seem that one may be punished for another's sin. For it is written (Ex 20,5): "I am . . . God . . . jealous, visiting the iniquity of the fathers upon the children, unto the third and fourth generation of them that hate Me"; and (Mt 23,35): "That upon you may come all the just blood that hath been shed upon the earth."
2. Further, human justice springs from Divine justice. Now, according to human justice, children are sometimes punished for their parents, as in the case of high treason. Therefore also according to Divine justice, one is punished for another's sin.
3. Further, if it be replied that the son is punished, not for the father's sin, but for his own, inasmuch as he imitates his father's wickedness; this would not be said of the children rather than of outsiders, who are punished in like manner as those whose crimes they imitate. It seems, therefore, that children are punished, not for their own sins, but for those of their parents.

On the contrary It is written (Ez 18,20): "The son shall not bear the iniquity of the father."
I answer that If we speak of that satisfactory punishment, which one takes upon oneself voluntarily, one may bear another's punishment, in so far as they are, in some way, one, as stated above (Article [7]). If, however, we speak of punishment inflicted on account of sin, inasmuch as it is penal, then each one is punished for his own sin only, because the sinful act is something personal. But if we speak of a punishment that is medicinal, in this way it does happen that one is punished for another's sin. For it has been stated (Article [7]) that ills sustained in bodily goods or even in the body itself, are medicinal punishments intended for the health of the soul. Wherefore there is no reason why one should not have such like punishments inflicted on one for another's sin, either by God or by man; e.g. on children for their parents, or on servants for their masters, inasmuch as they are their property so to speak; in such a way, however, that, if the children or the servants take part in the sin, this penal ill has the character of punishment in regard to both the one punished and the one he is punished for. But if they do not take part in the sin, it has the character of punishment in regard to the one for whom the punishment is borne, while, in regard to the one who is punished, it is merely medicinal (except accidentally, if he consent to the other's sin), since it is intended for the good of his soul, if he bears it patiently.With regard to spiritual punishments, these are not merely medicinal, because the good of the soul is not directed to a yet higher good. Consequently no one suffers loss in the goods of the soul without some fault of his own. Wherefore Augustine says (Ep ad Avit.) [*Ep. ad Auxilium, ccl.], such like punishments are not inflicted on one for another's sin, because, as regards the soul, the son is not the father's property. Hence the Lord assigns the reason for this by saying (Ez 18,4): "All souls are Mine."

Reply to Objection: 1. Both the passages quoted should, seemingly, be referred to temporal or bodily punishments, in so far as children are the property of their parents, and posterity, of their forefathers. Else, if they be referred to spiritual punishments, they must be understood in reference to the imitation of sin, wherefore in Exodus these words are added, "Of them that hate Me," and in the chapter quoted from Matthew (verse 32) we read: "Fill ye up then the measure of your fathers." The sins of the fathers are said to be punished in their children, because the latter are the more prone to sin through being brought up amid their parents' crimes, both by becoming accustomed to them, and by imitating their parents' example, conforming to their authority as it were. Moreover they deserve heavier punishment if, seeing the punishment of their parents, they fail to mend their ways. The text adds, "to the third and fourth generation," because men are wont to live long enough to see the third and fourth generation, so that both the children can witness their parents' sins so as to imitate them, and the parents can see their children's punishments so as to grieve for them.
2. The punishments which human justice inflicts on one for another's sin are bodily and temporal. They are also remedies or medicines against future sins, in order that either they who are punished, or others may be restrained from similar faults.
3. Those who are near of kin are said to be punished, rather than outsiders, for the sins of others, both because the punishment of kindred redounds somewhat upon those who sinned, as stated above, in so far as the child is the father's property, and because the examples and the punishments that occur in one's own household are more moving. Consequently when a man is brought up amid the sins of his parents, he is more eager to imitate them, and if he is not deterred by their punishments, he would seem to be the more obstinate, and, therefore, to deserve more severe punishment.


In the next place, since venial and mortal sins differ in respect of the debt of punishment, we must consider them. First, we shall consider venial sin as compared with mortal sin; secondly, we shall consider venial sin in itself.

Under the first head there are six points of inquiry:

(1) Whether venial sin is fittingly condivided with mortal sin?

(2) Whether they differ generically?

(3) Whether venial sin is a disposition to mortal sin?

(4) Whether a venial sin can become mortal?

(5) Whether a venial sin can become mortal by reason of an aggravating circumstance?

(6) Whether a mortal sin can become venial?

Whether venial sin is fittingly condivided with mortal sin?

Objection: 1. It would seem that venial sin is unfittingly condivided with mortal sin. For Augustine says (Contra Faust. xxii, 27): "Sin is a word, deed or desire contrary to the eternal law." But the fact of being against the eternal law makes a sin to be mortal. Consequently every sin is mortal. Therefore venial sin is not condivided with mortal sin.
2. Further, the Apostle says (1Co 10,31): "Whether you eat or drink, or whatever else you do; do all to the glory of God." Now whoever sins breaks this commandment, because sin is not done for God's glory. Consequently, since to break a commandment is to commit a mortal sin, it seems that whoever sins, sins mortally.
3. Further, whoever cleaves to a thing by love, cleaves either as enjoying it, or as using it, as Augustine states (De Doctr. Christ. i, 3,4). But no person, in sinning, cleaves to a mutable good as using it: because he does not refer it to that good which gives us happiness, which, properly speaking, is to use, according to Augustine (De Doctr. Christ. i, 3,4). Therefore whoever sins enjoys a mutable good. Now "to enjoy what we should use is human perverseness," as Augustine again says (Qq. lxxxiii, qu. 30). Therefore, since "perverseness" [*The Latin 'pervertere' means to overthrow, to destroy, hence 'perversion' of God's law is a mortal sin.] denotes a mortal sin, it seems that whoever sins, sins mortally.
4. Further, whoever approaches one term, from that very fact turns away from the opposite. Now whoever sins, approaches a mutable good, and, consequently turns away from the immutable good, so that he sins mortally. Therefore venial sin is unfittingly condivided with mortal sin.

On the contrary Augustine says (Tract. xli in Joan.), that "a crime is one that merits damnation, and a venial sin, one that does not." But a crime denotes a mortal sin. Therefore venial sin is fittingly condivided with mortal sin.
I answer that Certain terms do not appear to be mutually opposed, if taken in their proper sense, whereas they are opposed if taken metaphorically: thus "to smile" is not opposed to "being dry"; but if we speak of the smiling meadows when they are decked with flowers and fresh with green hues this is opposed to drought. In like manner if mortal be taken literally as referring to the death of the body, it does not imply opposition to venial, nor belong to the same genus. But if mortal be taken metaphorically, as applied to sin, it is opposed to that which is venial.For sin, being a sickness of the soul, as stated above (Question [71], Article [1], ad 3; Question [72], Article [5]; Question [74], Article [9], ad 2), is said to be mortal by comparison with a disease, which is said to be mortal, through causing an irreparable defect consisting in the corruption of a principle, as stated above (Question [72], Article [5]). Now the principle of the spiritual life, which is a life in accord with virtue, is the order to the last end, as stated above (Question [72], Article [5]; Question [87], Article [3]): and if this order be corrupted, it cannot be repaired by any intrinsic principle, but by the power of God alone, as stated above (Question [87], Article [3]), because disorders in things referred to the end, are repaired through the end, even as an error about conclusions can be repaired through the truth of the principles. Hence the defect of order to the last end cannot be repaired through something else as a higher principle, as neither can an error about principles. Wherefore such sins are called mortal, as being irreparable. On the other hand, sins which imply a disorder in things referred to the end, the order to the end itself being preserved, are reparable. These sins are called venial: because a sin receives its acquittal [veniam] when the debt of punishment is taken away, and this ceases when the sin ceases, as explained above (Question [87], Article [6]).Accordingly, mortal and venial are mutually opposed as reparable and irreparable: and I say this with reference to the intrinsic principle, but not to the Divine power, which can repair all diseases, whether of the body or of the soul. Therefore venial sin is fittingly condivided with mortal sin.

Reply to Objection: 1. The division of sin into venial and mortal is not a division of a genus into its species which have an equal share of the generic nature: but it is the division of an analogous term into its parts, of which it is predicated, of the one first, and of the other afterwards. Consequently the perfect notion of sin, which Augustine gives, applies to mortal sin. On the other hand, venial sin is called a sin, in reference to an imperfect notion of sin, and in relation to mortal sin: even as an accident is called a being, in relation to substance, in reference to the imperfect notion of being. For it is not "against" the law, since he who sins venially neither does what the law forbids, nor omits what the law prescribes to be done; but he acts "beside" the law, through not observing the mode of reason, which the law intends.
2. This precept of the Apostle is affirmative, and so it does not bind for all times. Consequently everyone who does not actually refer all his actions to the glory of God, does not therefore act against this precept. In order, therefore, to avoid mortal sin each time that one fails actually to refer an action to God's glory, it is enough to refer oneself and all that one has to God habitually. Now venial sin excludes only actual reference of the human act to God's glory, and not habitual reference: because it does not exclude charity, which refers man to God habitually. Therefore it does not follow that he who sins venially, sins mortally.
3. He that sins venially, cleaves to temporal good, not as enjoying it, because he does not fix his end in it, but as using it, by referring it to God, not actually but habitually.
4. Mutable good is not considered to be a term in contraposition to the immutable good, unless one's end is fixed therein: because what is referred to the end has not the character of finality.

Whether mortal and venial sin differ generically?

Objection: 1. It would seem that venial and mortal sin do not differ generically, so that some sins be generically mortal, and some generically venial. Because human acts are considered to be generically good or evil according to their matter or object, as stated above (Question [18], Article [2]). Now either mortal or venial sin may be committed in regard to any object or matter: since man can love any mutable good, either less than God, which may be a venial sin, or more than God, which is a mortal sin. Therefore venial and mortal sin do not differ generically.
2. Further, as stated above (Article [1]; Question [72], Article [5]; Question [87], Article [3]), a sin is called mortal when it is irreparable, venial when it can be repaired. Now irreparability belongs to sin committed out of malice, which, according to some, is irremissible: whereas reparability belongs to sins committed through weakness or ignorance, which are remissible. Therefore mortal and venial sin differ as sin committed through malice differs from sin committed through weakness or ignorance. But, in this respect, sins differ not in genus but in cause, as stated above (Question [77], Article [8], ad 1). Therefore venial and mortal sin do not differ generically.
3. Further, it was stated above (Question [74], Article [3], ad 3; Article [10]) that sudden movements both of the sensuality and of the reason are venial sins. But sudden movements occur in every kind of sin. Therefore no sins are generically venial.

On the contrary Augustine, in a sermon on Purgatory (De Sanctis, serm. xli), enumerates certain generic venial sins, and certain generic mortal sins.
I answer that Venial sin is so called from "venia" [pardon]. Consequently a sin may be called venial, first of all, because it has been pardoned: thus Ambrose says that "penance makes every sin venial": and this is called venial "from the result." Secondly, a sin is called venial because it does not contain anything either partially or totally, to prevent its being pardoned: partially, as when a sin contains something diminishing its guilt, e.g. a sin committed through weakness or ignorance: and this is called venial "from the cause": totally, through not destroying the order to the last end, wherefore it deserves temporal, but not everlasting punishment. It is of this venial sin that we wish to speak now.For as regards the first two, it is evident that they have no determinate genus: whereas venial sin, taken in the third sense, can have a determinate genus, so that one sin may be venial generically, and another generically mortal, according as the genus or species of an act is determined by its object. For, when the will is directed to a thing that is in itself contrary to charity, whereby man is directed to his last end, the sin is mortal by reason of its object. Consequently it is a mortal sin generically, whether it be contrary to the love of God, e.g. blasphemy, perjury, and the like, or against the love of one's neighbor, e.g. murder, adultery, and such like: wherefore such sins are mortal by reason of their genus. Sometimes, however, the sinner's will is directed to a thing containing a certain inordinateness, but which is not contrary to the love of God and one's neighbor, e.g. an idle word, excessive laughter, and so forth: and such sins are venial by reason of their genus.Nevertheless, since moral acts derive their character of goodness and malice, not only from their objects, but also from some disposition of the agent, as stated above (Question [18], Articles [4],6), it happens sometimes that a sin which is venial generically by reason of its object, becomes mortal on the part of the agent, either because he fixes his last end therein, or because he directs it to something that is a mortal sin in its own genus; for example, if a man direct an idle word to the commission of adultery. In like manner it may happen, on the part of the agent, that a sin generically mortal because venial, by reason of the act being imperfect, i.e. not deliberated by reason, which is the proper principle of an evil act, as we have said above in reference to sudden movements of unbelief.

Reply to Objection: 1. The very fact that anyone chooses something that is contrary to divine charity, proves that he prefers it to the love of God, and consequently, that he loves it more than he loves God. Hence it belongs to the genus of some sins, which are of themselves contrary to charity, that something is loved more than God; so that they are mortal by reason of their genus.
2. This argument considers those sins which are venial from their cause.
3. This argument considers those sins which are venial by reason of the imperfection of the act.

Summa Th. I-II EN Qu.87 a.4