Roman Catholic teaching
Rome has never denied that salvation is based upon grace, upon the world of Christ and upon faith. The Council of Trent affirmed that faith indeed is essential to justification — but also declared faith is not sufficient in itself to yield the result of justification. In its explanation of the loss of justification through “mortal sin,” it explicitly stated that a person in possession of saving faith can commit mortal sin. According to Rome, when a person commits mortal sin while in possession of true faith, faith is not lost but justification is. Thus, a person can have saving faith without justification. He can retain the faith but lose the justification by committing a mortal sin. He can then be restored to a state of justification through the sacrament of Penance, and more specifically, its third aspect, satisfaction.
(The Sixth Session of the Council of Trent, Chapter XIV, emphasis added) “As regards those who, by sin, have fallen from the received grace of Justification, they may be again justified, when, God exciting them, through the sacrament of Penance they shall have attained to the recovery, by the merit of Christ, of the grace lost: for this manner of Justification is of the fallen the reparation: which the holy Fathers have aptly called a second plank after the shipwreck of grace lost. For, on behalf of those who fall into sins after baptism, Christ Jesus instituted the sacrament of Penance, when He said, Receive ye the Holy Ghost, whose sins you shall forgive, they are forgiven them, and whose sins you shall retain, they are retained. Whence it is to be taught, that the penitence of a Christian, after his fall, is very different from that at (his) baptism; and that therein are included not only a cessation from sins, and a detestation thereof, or, a contrite and humble heart, but also the sacramental confession of the said sins,-at least in desire, and to be made in its season,-and sacerdotal absolution; and likewise satisfaction by fasts, alms, prayers, and the other pious exercises of a spiritual life; not indeed for the eternal punishment,-which is, together with the guilt, remitted, either by the sacrament, or by the desire of the sacrament,-but for the temporal punishment, which, as the sacred writings teach, is not always wholly remitted, as is done in baptism, to those who, ungrateful to the grace of God which they have received, have grieved the Holy Spirit, and have not feared to violate the temple of God. Concerning which penitence it is written; Be mindful whence thou art fallen; do penance, and do the first works. And again; The sorrow that is according to God worketh penance steadfast unto salvation. And again; Do penance, and bring forth fruits worthy of penance.”
(CCC 980) “It is through the sacrament of Penance that the baptized can be reconciled with God and with the Church: Penance has rightly been called by the holy Fathers ‘a laborious kind of baptism.’ This sacrament of Penance is necessary for salvation for those who have fallen after Baptism, just as Baptism is necessary for salvation for those who have not yet been reborn.”
(CCC 1815) “The gift of faith remains in one who has not sinned against it. But ‘faith apart from works is dead’: when it is deprived of hope and love, faith does not fully unite the believer to Christ and does not make him a living member of his Body.”
(CCC 1446) “Christ instituted the sacrament of Penance for all sinful members of his Church: above all for those who, since Baptism, have fallen into grave sin, and have thus lost their baptismal grace and wounded ecclesial communion. It is to them that the sacrament of Penance offers a new possibility to convert and to recover the grace of justification. the Fathers of the Church present this sacrament as ‘the second plank [of salvation] after the shipwreck which is the loss of grace.'”
The Roman communion taught that faith is a necessary condition for salvation. At the Council of Trent, the Roman Catholic authorities declared that faith affords three things: the initium, the fundamentum and the radix. That is, faith is the beginning of justification, the foundation for justification, and the root of justification. But Rome held that a person can have true faith and still not be justified, because there was much more to the Roman system. For instance, Rome differentiates between mortal sin and venial sin, and condign merit and congruous merit.
The Roman view of the gospel, as expressed at Trent and reaffirmed in the Catechism (CCC 183, 1129, 1815, 2002), was that justification is accomplished through the sacraments. Initially, the recipient must accept and cooperate in baptism, by which he receives justifying grace. He retains that grace until he commits mortal sin. Mortal sin is called “mortal” because it kills the grace of justification. The sinner then must be justified a second time. That happens through the sacrament of Penance.
The fundamental difference was that Trent said that God does not justify anyone until real righteousness “inheres” within the person. In other words, God does not declare a person righteous until he or she is righteous. So, according to Roman Catholic doctrine, justification depends on a person’s sanctification. By contrast, the Reformers said justification is based on the imputation of the righteousness of Jesus. Our righteousness is not inherent, but must come from someone else. It is, as Luther said, extra nos — an “alien” righteousness. The only ground by which a person can be saved is Jesus’ righteousness, which is reckoned to him, or credited to his account, when he believes.