Summa Theologiae Moralis, vol. I: De Principiis

S. Th. I-II, q. 84, a. 2; q. 87, a. 4; II-II, q. 162, a. 6; q. 34, a. 2; q. 195, a. 1, ad 1; III, q. 1, a. 2 and ad 2; Suppl. q. 99, a. 1; III Sent. d. 20, q. 1, a. 2; II Sent. d. 42, q. 1, a. 2, 5 and ad 2; De Verit. q. 28, a. 2 and ad 5; de Malo q. 2, a. 9, ad 5.

534. Mortal sin is the gravest evil, whether considered on the part of God, or on the part of man. A. As to God:

1°) It is the greatest injury done to the Supreme Good, by which man makes the last end and seeks happiness in a creature and prefers it to God, despises, dishonors, turns away from, and hates him, despises his love and friendship, and so violates the right of God which requires that we refer all our actions and all the creatures we use to him; whence sin implicitly contains the malice of hatred of God¹, of irreligion, of contumely toward the all-present God (Ps. L, 6) and of idolatry (John XII, 43; Rom. II, 23; Is. LII, 5; XLIII, 24; Ezech. XXXVI, 20; Ps. CXXXVIII, 8; Ps. I, 6; I Kings II, 30; Lev. VI, 2; XXVI, 15; Phil. III, 19; Gal. V; C. Trid. sess. 6, c. 5).

2°) It is rash disobedience and bold rebellion against infinite majesty, and offense and contempt of the supreme legislator, of almighty lord, judge and king, of his very will and law, which it contradicts and refuses obedience and subjection; whence it implicitly contains the malice of pride (Gen. II, 16; III, 1; Heb. II, 2; Jer. II, 20; Is. XXXIII, 14; Wis. V, 2-15; I John III, 4; Job XV, 25; Gal. VI, 7).

3°) It is the greatest ingratitude toward the distinguished benefactor, whose benefits we use to offend him: against the Father creating, preserving, providing, and adopting us as sons and calling us to eternal life; against the Son brother and redeemer (Heb. VI, 5) whose death's cause he renews; against the Holy Spirit sanctifying, friend and inhabitant of our soul. Whence it implicitly contains contempt of the friendship and presence of him whom we cast away from us, and the malice of sacrilege because it violates the soul consecrated to God, and of infidelity toward the covenant (Ezech. II, 3; Jer. XXXI, 32; Is. I, 2; Heb. X, 26-31; Eph. IV, 3) with God, the duty and the offices thence following (Is. V; Jer. II, 32; III, 1; II Kings XII, 7; Heb. VI, 6; I Cor. III, 17; VI, 19; II Cor. VI, 16).

B. As to man it is:

1°) T urpitudo, dishonor and folly (Ps. XLVIII, 13; LXVIII, 6; Wis. V, 2-13), as being an evil against our nature and reason (q. 71, a. 2).

2°) Spiritual suicide, as depriving of supernatural light and life (I John III, 15, 20; II, 9; III, 14; Tob. XII, 10).

3°) Deformity depriving the soul of natural and supernatural beauty, whence it dishonors the one acting and renders him worthy of contempt (Ps. XLVIII, 13).

4°) Slavery of the devil (I John III, 8; Jer. II, 19; Rom. VI, 6; II Pet. II, 19), because man does the work of the devil and subjects himself to him consenting, and thus renders himself more liable to temptations.

535. Observations. — 1°) The aforesaid malices are not found in mortal sin of themselves except implicitly, and therefore are at most voluntary in cause and virtually; whence they are not to be explained in confession, as being the condition of every sin; unless one were to intend explicitly and formally some of them in himself, because then there would be sin of the species intended.

2°) Several malices of mortal sin are also found in venial sin, but only analogically, imperfectly, and in a qualified sense (a. 1, ad 1). Whence, if it is a light evil in respect of mortal sin, in itself however it is very grave.

536. In what sense mortal sin is infinite. — Mortal sin:

1°) On the part of conversion is not infinite, because both the act of man and the created good toward which it tends are finite.

2°) On the part of aversion from the Infinite good:

a) is not of infinite malice: for infinite evil is pure evil, without any mixture of good; whence for sin to have infinite malice, man would have to tend to evil inasmuch as it is evil; which is impossible;

b) nor as it is an offense or injury of the infinite God, does it seem simply infinite: for the gravity of offense seems to be measured not only from the dignity of the offended God but also on the part of the offending man. But the will tends to the object as it is in the intellect, and therefore by sin does not offend God as he is in himself simply infinite but as he is known very imperfectly by the intellect. Therefore by sin an injury simply infinite is not inflicted on God.

c) Yet that offense is infinite in a qualified sense, and especially relatively to our reparation: for it is contempt of an infinite person; but injury is estimated also from the dignity of the offended person, satisfaction however only from the dignity of the satisfying person, and on the other hand the distance between God and men is infinite; therefore the injury of sin is estimated infinitely more than every reparation of man (even made by grace and charity). Therefore man cannot satisfy de condigno for sin. And so

d) mortal sin is of itself of infinite duration, because by its nature it is irreparable, and its malice in us remains without end and lasts forever. Whence eternal punishment of infinite duration is also due to it.

537. The gravity of mortal sin is described in Scripture. — A. In the Old Testament: 1°) From the beginning sin is presented as disobedience or transgression of the divine precept, which is strictly punished (Gen. II, 16; III, 11; 14-19; IV, 9-16; VI, 5-7; 11-13).

2°) After the election of the people of Israel and the promise of the divine law by Moses, sin is considered as rebellion against the supreme Legislator and King of the elect people (Exod. XIX, 5-8; XXIV, 3, 7), and as contempt of the law of the Lord (Lev. XXVI, 15). Among sins the chief is idolatry (Exod. XX, 3-5), which is also severely punished (Exod. XXXII, 30-35); but other graver offenses are punished with the penalty of death (Lev. XVIII, 29; XX, 6-27).

In order that the rude and uncultivated people might be turned away from sin: a) especially and above all the law had the sanction of the promise of temporal goods for those keeping it, and for those violating it threats of grave evils (Deut. VII, 11-26; X, 12-22; XI, 13-28); — b) there was added also the motive of gratitude and love toward God (Deut. XI, 1; VIII, 2-20); — c) as also of solidarity, inasmuch as God would punish the sins of individuals even in their posterity or in the nation (Exod. XX, 5).

3°) From the time of the Prophets sin is more expressly presented as offense of God, of neighbor, or of one's own reason:

a) toward God it is ingratitude, contempt of benefits and of the Father, and infidelity (Is. I, 2; Jer. II, 4-37; III, 1);

b) toward neighbor it is injustice (Amos II, 7);

c) toward ourselves, folly (Tob. XII, 10; Wis. V, 2-13; X, 8).

wherefore the Prophets insist on interior penitence of heart by which the mercy of the Lord will be obtained (Joel, II, 12-13; Ps. L, 19).

B. In the New Testament: 1°) Christ, who came that, as the Lamb of God, he might take away the sins of the world (John I, 29), supposes the nature of sin as known, but denounces the gravity of certain sins, and the extension of sin to certain acts which were reputed as honest: namely the malice of hypocrisy, scandal, infidelity, and blasphemy against the Holy Spirit (Mt. XXIII, 5-32; XVIII, 16; XII, 31-32; Mk. III, 29; XVI, 16; Lk. XVII, 1-2). And he urgently proclaims the inordination of interior sin of the heart (Mt. XV, 19-20).

2°) S. Paul especially shows the effects of sin. It is namely slavery from which we are freed by grace (Rom. VI, 17-18); it is the cause of death (Rom. V, 12; VI, 23; VIII, 13), and of darkness (Col. I, 13; Eph. V, 8; II Cor. VI, 14); it is a transgression that will be punished by a terrible judgment (Heb. II, 2), inasmuch as the sinner tramples under foot the Son of God and grieves the Spirit (Heb. X, 26-31; Eph. IV, 30).

3°) S. John, however, the beloved disciple of him who appeared to take away our sins (I John III, 5) and whom we have as advocate with the Father, where he is the propitiation for our sins (II, 1-2), illustrates not only the effects but rather the causes of sin: they are iniquity (V, 17; I, 9); the devil: he who does sin is of the devil (III, 8; cf. John VIII, 44); and the world, because the whole is placed in the wicked one (V, 19) and all that is in it is concupiscence of the flesh, and concupiscence of the eyes, and pride of life (II, 16). But the sinner walks in darkness and lacks light (I, 6; II, 9, 11), remains in death and does not have eternal life in himself (III, 14-15; V, 12), nor the charity of God (III, 17; IV, 8, 20). Two sins especially he says are to be avoided: sin against the love of neighbor (II, 9-11; III, 15-17; IV, 8), and sin against Christ, by denying his divinity (II, 22; IV, 15; V, 10-12). This is sin unto death (V, 16-17), so grave that prayers are not offered for him who committed it (16).