Summa summae S. Thomae, Tomus II

St. Thomas, qq. 88 and 89.

Mortal sin is called that which brings death to the soul, depriving it of grace, and it is worthy of eternal punishment. Venial sin, strictly taken, is called that which does not exclude from the subject the principle of pardon, which is grace.

The heretics of later times, Wiclef, Luther, Melancthon, Calvin, etc., taught that all sins are mortal by their nature and are of themselves onto death of the soul and eternal punishment; but in fact do not inflict these upon the predestined and the faithful, from the mercy of God; and thus venial sin is not distinguished from mortal sin by its nature, but either from a law or mercy enacted by God, or from the condition of the sinning person.

I say: There are given venial sins distinct from mortals by their own nature, not only from the condition of the sinner or from the mercy of God¹.

It is proved 1° from Scripture. In various places of Scripture, some sins, without any respect to persons, are compared to most light things, others to most grave things: thus Matth., XXIII, 24, some are compared to a gnat, others to a camel; Luc., VI, 41, some to a mote, others to a beam; I Cor., III, 12, some to hay and stubble built upon the foundation which is Christ. But, if all sins were of themselves mortal, some would be ill compared to those minute things, while others are compared to most grave things; for that ought not to be called minute and light which inflicts of itself death of the soul and eternal hell. Therefore, as neither can a mote of itself blind, nor a gnat suffocate, nor hay or straw overthrow the foundation; so neither do sins compared to those minute things kill by their nature, and constitute the guilty one in eternal death.

It is proved 2°. The council of Trent defined the same truth session VI, chapter 11, canons 7, 23 and 25, and session XIV, chapter 5: read². And finally the Sovereign Pontiffs St. Pius V and Greg. XIII condemned this proposition: « There is no sin venial by its nature, but every sin merits eternal punishment. » It is the 20th among the Baianists.

It is proved by a manifold reason. The first is founded in Scripture. According to Scripture, God does not impute nor punish sins otherwise than they deserve of themselves, as is clear from that Psal., LXI, 13: For thou wilt render to every man according to his works. And II Cor., V, 10: That every one may receive the proper things of the body, according as he hath done. Therefore, if there are sins which God does not punish with eternal punishment, they do not merit it of themselves.

The second. Sin is a certain infirmity of the soul, according to that Psal., VI, 3: Have mercy on me, O Lord, for I am weak. Therefore, as there are certain infirmities of the body mortal of themselves, others not, so also infirmities of the soul.

The third. Among friends there are light offenses which by their nature, and not only from the favor of the friend, do not dissolve friendship. Therefore similarly toward God. Will anyone believe that a just man and friend of God, by the nature of an idle word or superfluous laughter, incurs the hatred of God and liability to eternal gehenna?

The fourth, special against the heretics. Adam, David and St. Peter were faithful and predestined. Yet nevertheless certain of their sins were truly mortal, and reckoned and imputed as such, namely the eating of the forbidden fruit in Adam, adultery in David, denial of Christ in St. Peter. Nor indeed do I think anyone denies that Adam, David and St. Peter lost by these sins the friendship of God and incurred liability to eternal punishment, until they were expiated by penance. Of the sin of Adam so understand Ambros., book de Paradiso, c. 9, and Aug., book XIII de Civit., c. 12. Of the adultery of David so judges the same Aug., in Psal. L. Of the sin of St. Peter similarly understands the same Aug., tract. 66 in Ioann., n. 2, where of St. Peter he says: « He died denying, and rose again weeping. » Therefore venial sins are not distinguished from mortals by the sole condition of the sinner.

It is confirmed. Dignity of person does not diminish, but augments sin, as St. Thomas proves above q. 73, a. 10, c, and we from him in the same place. Therefore sin is not venial because it is committed by a faithful man or one predestined.