The Roman Catholic Church grants these indulgences after the guilt of sin and its punishment of eternal damnation have been remitted by the sacrament of reconciliation, also known as penance, or by perfect contrition. Under Roman Catholic theology, the salvation made possible by Jesus Christ allows the faithful sinner eventual admittance to Heaven. Baptism wipes the sinner's slate clean and results in the full forgiveness of sins; but any sin committed after baptism incurs a penalty that has not been forgiven. Serious sins are mortal sins; they extinguish sanctifying grace in the believer's soul, and doom the sinner to Hell. For these sinners, grace must be restored by perfect contrition or the sacrament of Reconciliation; even so, there remains a penalty owed to God that must be expiated in this world or in the afterlife. Other, less serious sins, are venial sins and incur a penalty owed to God even if they do not forfeit salvation. Indulgences remove some or all of these temporal penalties owed on account of the sins of the faithful.
Indulgences are "plenary" or "partial;" "plenary," when they remit all of the temporal punishment due for sin; and "partial," when a part of that punishment is remitted. A partial indulgence is stated as a term of days, weeks, months, or years; these terms mean that as much of the temporal punishment for sins is remitted as would be expiated by performance of a canonical penance for that period of time.
Indulgences can be applied either to the penitent's own sins, or for the alleviation of the penance of souls in Purgatory. Obtaining an indulgence for another living person is disallowed by canon law. To successfully apply an indulgence to your own sins, you must be a baptised Christian, a member of the Roman Catholic Church, not subject to excommunication, and have the intention of performing the work for which the indulgence is granted.
The doctrine of indulgences is founded on three doctrines of the Roman Catholic Church:
The doctrine of indulgences has historically been one of the more controversial teachings in Roman Catholic soteriology. The ability to offer a full pardon of the punishment due for sins has been used by the Roman Catholic Church to motivate its faithful to do a number of things over history. A plenary indulgence was proclaimed by Pope Urban II in 1095, and by several of his successors, to anyone who went on the Crusades to deliver the Holy Land from the Saracens, or who died along the way.
In 1517, Pope Leo X offered indulgences in exchange for money which was being raised to rebuild St. Peter's Basilica in Rome. The aggressive marketing practices of Johann Tetzel in promoting this cause provoked Martin Luther to nail his 95 theses to the church door at Wittenberg, protesting what he saw as the purchase and sale of salvation. From this controversy the Protestant Reformation was launched.
Because the underlying doctrine of salvation differs from the Roman Catholic model, indulgences do not exist in Eastern Orthodoxy or in Protestantism.