Summa Theologiae

Thomas Aquinas

I-II 88-89 (selected questions on mortal and venial sin)

Question 88

On venial sin in comparison with mortal sin

Article 1

Whether it is fitting to distinguish venial from mortal sin


It seems that it is not fitting to distinguish venial from mortal sin.

1. For Augustine says, “Sin is a deed or word or desire contrary to the eternal law” (Against Faustus). But to be contrary to the eternal law, causes a sin to be mortal. Therefore every sin is mortal. Therefore venial sin is not distinct from mortal sin.

2. Further, the Apostle says, “Whether you eat, or drink, or whatever else you do, do all for the glory of God.” (1 Cor 10:31) But whoever sins, acts contrary to this precept, since sin is not done for the glory of God. Therefore since to act contrary to a precept is a mortal sin, it seems that whoever sins, sins mortally.

3. Further, whoever clings to a thing with love, clings to it either as enjoying it, or as using it, as is evident from Augustine in On Christian Doctrine. But no one who is sinning clings to a changeable good as though using it; for he does not refer it to that good which makes us blessed, which is properly speaking to use a thing, as Augustine says in the same place. Therefore whoever sins, enjoys a changeable good. But “To enjoy things that should be used, is human perversity,” as Augustine says in Eighty-three Questions. Therefore since perversity names mortal sin, it seems that whoever sins, sins mortally.

4. Further, whoever goes towards one term, by that very fact goes away from the other. But whoever sins, goes towards a changeable good. Therefore he goes away from the unchangeable good. Therefore he sins mortally. Therefore it is not fitting to distinguish venial from mortal sin.

On the contrary:

Augustine says, “a crime is that which merits damnation, while that which does not merit damnation is venial.” (Homily 41 on John) But “crime” names a mortal sin. Therefore it is fitting to distinguish venial from mortal sin.


It should be said... in the sense in which “mortal” is said of sins, [i.e., as referring to spiritual death], mortal is opposed to venial. For since sin is a certain sickness of soul, as was established above, a sin is called mortal by way of likeness to a disease, which is called mortal because, by the corruption of a principle, it causes an irreparable defect, as was said above. Now the principle of spiritual life, which is life in accord with virtue, is the order to the last end, as was said above. If this order is corrupted, it cannot be remedied by an intrinsic principle, but only by divine power, as was said above; for disorder in things that are related to the end, is remedied on the basis of the end, as an error about conclusions can be remedied on the basis of the truth of the principles. Therefore the defect of order to the last end cannot be remedied by something else that would be a more fundamental principle, just as an error in regard to the principles cannot be so remedied. And therefore sins of this kind are called mortal, as being irreparable. But sins that have a disorder in regard to things ordered to the end, while keeping the order to the last end, are reparable. And these sins are called venial; for a sin receives pardon [veniam] when the debt of punishment is taken away, which ceases when the sin ceases, as was said above.

Accordingly, mortal and venial sin are opposed as reparable and irreparable—I mean by way of intrinsic principle, not in relation to the divine power, which can heal every bodily and spiritual disease. And for this reason it is fitting to distinguish venial from mortal sin.

Replies to objections:

1. To the first, therefore, it should be said that the distinction of venial and mortal sin is not the division of a genus into species, which equally share the account of the genus. But it is the division of something analogous into the things of which it is predicated according to a certain order: one firstly, and the other secondly. And therefore the perfect account of sin, which Augustine gives, belongs to mortal sin. But venial sin is called sin according to an imperfect account, and in relation to mortal sin, as an accident is called a being in relation to substance, according to an imperfect account of being. For venial sin is not contrary to the law, since he who sins venially neither does what the law prohibits, nor fails to do what the law prescribes. But he acts “besides” the law, since he does not observe the measure of reason that the law intends.

2. To the second it should be said that this precept of the Apostle is positive, and so does not bind at all times. Therefore not everyone who does not actually refer all his actions to the glory of God, acts against this precept. In order to avoid sinning mortally when one does not actually refer an act to the glory of God, it suffices for someone to habitually refer himself and all that he has to God. But venial sin does not exclude the habitual ordering of human action to the glory of God, but only the actual ordering; for it does not exclude charity, which orders us habitually to God. Hence it does not follow that he who sins venially, sins mortally.

3. To the third it should be said that he who sins venially clings to a temporal good not as enjoying it, since he does not place his end in it, but as using it, referring it to God not actually, but habitually.

4. To the fourth it should be said that a changeable good is not taken as a term, placed in opposition to the unchangeable good, unless one places one’s end in it. For that which is ordered to the end does not have the account of a term.

Article 2

Whether mortal and venial sin differ in genus

It seems that venial and mortal sin do not differ in genus, namely so that some sin is mortal according to genus, and some sin is venial according to genus.


It should be said 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 (q. 18, aa. 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.

Article 3

Whether venial sin is a disposition to mortal sin


It should be said that a disposition is a kind of cause; wherefore as there is a twofold manner of cause, so is there a twofold manner of disposition. For there is a cause which moves directly to the production of the effect, as a hot thing heats: and there is a cause which moves indirectly, by removing an obstacle, as he who displaces a pillar is said to displace the stone that rests on it. Accordingly an act of sin disposes to something in two ways. First, directly, and thus it disposes to an act of like species. In this way, a sin generically venial does not, primarily and of its nature, dispose to a sin generically mortal, for they differ in species. Nevertheless, in this same way, a venial sin can dispose, by way of consequence, to a sin which is mortal on the part of the agent: because the disposition or habit may be so far strengthened by acts of venial sin, that the lust of sinning increases, and the sinner fixes his end in that venial sin: since the end for one who has a habit, as such, is to work according to that habit; and the consequence will be that, by sinning often venially, he becomes disposed to a mortal sin. Secondly, a human act disposes to something by removing an obstacle thereto. In this way a sin generically venial can dispose to a sin generically mortal. Because he that commits a sin generically venial, turns aside from some particular order; and through accustoming his will not to be subject to the due order in lesser matters, is disposed not to subject his will even to the order of the last end, by choosing something that is a mortal sin in its genus.

Article 6

Whether a mortal sin can become venial


It seems that a mortal sin can become venial.

2. For venial and mortal sin are said to differ in this, that he who sins mortally loves a creature more than God, while he who sins venially loves the creature less than God. Now it may happen that a person in committing a sin generically mortal, loves a creature less than God; for instance, if anyone being ignorant that simple fornication is a mortal sin, and contrary to the love of God, commits the sin of fornication, yet so as to be ready, for the love of God, to refrain from that sin if he knew that by committing it he was acting counter to the love of God. Therefore his will be a venial sin; and accordingly a mortal sin can become venial.


It should be said that venial and mortal differ as perfect and imperfect in the genus of sin, as stated above (a. 1, ad 1). Now the imperfect can become perfect, by some sort of addition: and, consequently, a venial sin can become mortal, by the addition of some deformity pertaining to the genus of mortal sin, as when a man utters an idle word for the purpose of fornication. On the other hand, the perfect cannot become imperfect, by addition; and so a mortal sin cannot become venial, by the addition of a deformity pertaining to the genus of venial sin, for the sin is not diminished if a man commit fornication in order to utter an idle word; rather is it aggravated by the additional deformity.

Nevertheless a sin which is generically mortal, can become venial by reason of the imperfection of the act, because then it does not completely fulfill the conditions of a moral act, since it is not a deliberate, but a sudden act, as is evident from what we have said above (a. 2). This happens by a kind of subtraction, namely, of deliberate reason. And since a moral act takes its species from deliberate reason, the result is that by such a subtraction the species of the act is destroyed.

Replies to objections:

2. To the second it should be said that if the ignorance be such as to excuse sin altogether, as the ignorance of a madman or an imbecile, then he that commits fornication in a state of such ignorance, commits no sin either mortal or venial. But if the ignorance be not invincible, then the ignorance itself is a sin, and contains within itself the lack of the love of God, insofar as a man neglects to learn those things whereby he can safeguard himself in the love of God.

Question 89

Question 89

On venial sin according to itself

Article 6

Whether venial sin can be in anyone with original sin alone


It seems that venial sin can be in a man with original sin alone.

3. For it is possible to fix the time at which a child is first able to commit an actual sin: and when the child comes to that time, it can stay a short time at least, without committing a mortal sin, because this happens in the worst criminals. Now it is possible for the child to sin venially during that space of time, however short it may be. Therefore venial sin can be in anyone with original sin alone and without mortal sin.

On the contrary:

Man is punished for original sin in the children’s limbo, where there is no pain of sense as we shall state further on (II-II, q. 69, a. 6): whereas men are punished in hell for no other than mortal sin. Therefore there will be no place where a man can be punished for venial sin with no other than original sin.


It should be said that it is impossible for venial sin to be in anyone with original sin alone, and without mortal sin. The reason for this is because before a man comes to the age of discretion, the lack of years hinders the use of reason and excuses him from mortal sin, wherefore, much more does it excuse him from venial sin, if he does anything which is such generically. But when he begins to have the use of reason, he is not entirely excused from the guilt of venial or mortal sin. Now the first thing that occurs to a man to think about then, is to deliberate about himself. And if he then direct himself to the due end, he will, by means of grace, receive the remission of original sin: whereas if he does not then direct himself to the due end, and as far as he is capable of discretion at that particular age, he will sin mortally, for through not doing that which is in his power to do. Accordingly thenceforward there cannot be venial sin in him without mortal, until afterwards all sin shall have been remitted to him through grace.

Replies to objections:

3. To the third it should be said that the child that is beginning to have the use of reason can refrain from other mortal sins for a time, but it is not free from the aforesaid sin of omission, unless it turns to God as soon as possible. For the first thing that occurs to a man who has discretion, is to think of himself, and to direct other things to himself as to their end, since the end is the first thing in the intention. Therefore this is the time when man is bound by God’s affirmative precept, which the Lord expressed by saying (Zach. 1:3): “Turn ye to me . . . and I will turn to you.”

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