1. The Council of Trent teaches definitively on original sin in a decree devoted to this subject.5 In doing so, it prescinds from the case of Mary (see DS 1516/792). Its essential teaching is in five articles (see DS 1511–15/788–92).
2. First, the Council asserts that the first man, Man (Adam), was constituted in justice and holiness, that he disobeyed a divine command, that he thereby lost justice and holiness and incurred as punishment the death with which God had threatened him. The Council teaches that with death Man became a slave to the devil, and that he was as a whole, both body and soul, changed for the worse by the offense of this sin (cf. S.t., 1, q. 95, a. 1; 1–2, q. 80, a. 4; q. 83; 2–2, q. 164, a. 1; 3, q. 49, a. 2).
The proposition that Man was changed as a whole for the worse is partially quoted from a definition of the sixth-century Second Council of Orange, which explicitly holds a point Trent does not explicitly mention: that the freedom of Man’s soul did not remain untouched by this sin (see DS 371/174).
3. Second, Trent asserts that Man’s sin was injurious to his descendants as well as to himself, that he lost holiness and justice for us as well as himself, and that he passed on to the whole of humankind sin itself, which is death of the soul, and not merely death and punishment of the body (cf. S.t., 1–2, q. 81, a. 1; q. 82, aa. 1, 3; q. 83, a. 3; S.c.g., 4, 50). Trent holds that the contradictory of this teaching is incompatible with the teaching of St. Paul (Rom 5.12).
4. Third, Trent asserts that the sin of Man is one in origin and is communicated to all men and women by propagation, not by imitation, that this sin is in all humankind and also is each individual’s sin. The Council teaches that this sin is not taken away by the powers of nature, that its only remedy is the unique mediator and Lord Jesus Christ who reconciles us to God in his blood, and that the merit of our Lord is applied to adults and infants alike through the sacrament of baptism (cf. S.t., 1–2, q. 81, aa. 1, 3; q. 82, aa. 1, 4; 3, q. 1, aa. 2, 4; q. 49, aa. 1–5; q. 69, aa. 1, 5; S.c.g., 4, 50).
5. Fourth, Trent asserts that it is right to baptize infants and cleanse them of original sin, for they really do contract it; it is sin in the true sense, and it must be expiated (cf. S.t., 3, q. 68, a. 9). This article also asserts that the Church has always understood St. Paul (Rom 5.12) to teach the universality of original sin, and so the universal need for redemption.
6. Fifth, Trent asserts that through the grace of our Lord Jesus original sin really is taken away, not merely covered over, that concupiscence (a tendency to sin) remains in the baptized, but that concupiscence is not sin in the true and proper sense of the word; it is only an effect of sin which inclines to sin (cf. S.t., 1–2, q. 82, a. 3; q. 110, a. 1; q. 113, aa. 1, 6).
In support of its teaching that baptism really takes away sin, the Council also inserts in this article an argument based on various passages of Scripture. This argument is aimed against those who did not recognize the full effect of the redemption worked by God through our Lord Jesus.
7. The Second Council of Orange, which Trent intends to follow, makes explicit one further, important point.6 It gives a reason, not mentioned by Trent, why it would be inappropriate to say that the punishment for original sin, but not sin itself, was transmitted to Man’s descendants: namely, that this would be to attribute an injustice to God (see DS 372/175). In other words, if we share in the punishment for Man’s sin, we must also somehow share in the sin itself, since otherwise God would be punishing us unfairly for a sin in no way our own (cf. S.t., 1–2, q. 81, a. 1; q. 83, a. 1; S.c.g., 4, 52).
Trent stresses the exclusivity of Christ’s mediatorship, leaving no question that no one is saved except in him. Our Lord Jesus saves us from sin, from death, and from the power of the devil. By Jesus’ redemptive work, effective in us through baptism, we truly are freed from sin, although unruly desire, which is an effect of sin, remains in us.
Although Vatican II has no extensive treatment of original sin, the recent Council in many places takes for granted the traditional teaching, which Trent defined, and alludes to its various aspects (see LG 2, 55–56, DV 3, AA 7, and GS 13, 18, 22). In the “Credo of the People of God,” Paul VI summarized Trent’s teaching in all its essentials, and very clearly reaffirmed it.7
5. The following studies by A. Vanneste are helpful in understanding the decree of Trent in its historical context: “La Préhistoire du Décret du Concile de Trente sur le péché originel,” Nouvelle Revue Théologique, 86 (1964), 355–68, 490–510; “Le Décret du Concile de Trente sur le péché originel,” Nouvelle Revue Théologique, 87 (1965), 688–726.
6. On the source of this position and the relation between Second Orange and Trent, see John P. Redding, The Influence of St. Augustine on the Doctrine of the II Council of Orange Concerning Original Sin (Washington: Catholic University of America, 1939), 50–68.
7. See 60 AAS (1968) 439; for a helpful commentary on this section of Paul VI’s Credo, see Candido Pozo, S.J., The Credo of the People of God: A Theological Commentary, trans. Mark A. Pilon (Chicago: Franciscan Herald Press, 1979), 103–18.