Indulgences replaced the severe penances of the early church, or, to express it more exactly, they replaced the shortening of those penances that was allowed at the intercession of those imprisoned and those awaiting martyrdom for the faith.
The Catholic doctrine of the Communion of Saints teaches that this work of cleansing or sanctification does not have to be done entirely by the person directly concerned, since all Christians, living and dead, are united as a single body that has Christ as head. The holiness of one profits others, well beyond the harm that the sin of one could cause others. Thus through the communion of saints, recourse not only to the merits of the saints in heaven but above all to those of Christ himself lets the contrite sinner be more promptly and efficaciously purified of the punishments for sin.
In view of the power of binding or loosing granted by Christ, the Church considers that it may administer to those under its jurisdiction the benefits of these merits in consideration of prayer or other pious works undertaken by the faithful. This the Church does for individual Christians, not simply to aid them, but also to spur them to works of devotion, penance, and charity.
Since those who have died are also members of the communion of saints, it is the belief of the Catholic Church that the living can help those whose purification from their sins is not yet completed not only by prayer but also by obtaining indulgences for them. Since the Church on earth has no jurisdiction over the dead, indulgences can be gained for them only per modum suffragii, i.e. by an act of intercession.
An indulgence may be plenary or partial, according as it remits all or only part of the temporal punishment that at that moment is due for sin. To gain a plenary indulgence, a person must exclude all attachment to sin of any kind, even venial sin, must perform the work or say the prayer for which the indulgence is granted, and must also fulfil the three conditions of sacramental confession, Eucharistic communion and praying for the intentions of the Pope. The minimum condition for gaining a partial indulgence is to be contrite in heart: on this condition, a Catholic who performs the work or recites the prayer in question is granted, through the Church, remission of temporal punishment of the same worth as is obtained by the person's own action.
In response to suggestions made at the Second Vatican Council, Pope Paul VI substantially revised the practical application of the traditional doctrine, making it clear that the Church's aim was not merely to help the faithful make due satisfaction for their sins, but chiefly to bring them to greater fervour of charity; it was for this purpose that he decreed that partial indulgences simply supplement, and to the same degree, the remission that the person performing the indulgenced action has already gained by the charity and contrition with which he does it. Previously, partial indulgences were granted as the equivalent of a certain number of days, months, "quarantines (Lent-like forty-day periods) or years of canonical penance. Those who did not understand these terms sometimes misinterpreted them as meaning a reduction of that length of stay in Purgatory.
The abolition of this classification by years and days made it clearer than before that repentance and faith are required not only for remission of eternal punishment for mortal sin but also for remission of temporal punishment for sin. Pope Paul VI wrote: "Indulgences cannot be gained without a sincere conversion of outlook and unity with God".
Among the particular grants, which, on closer inspection, will be seen to be included in one or more of the four general grants, especially the first, the Enchiridion Indulgentiarum draws special attention to four activities for which a plenary indulgence can be gained on any day, though only once a day:
A plenary indulgence may also be gained on some occasions, which are not everyday occurrences. They include:
The prayers specifically mentioned in the Enchiridion Indulgentiarum are not of the Latin Rite tradition alone, but also from the traditions of the Eastern Catholic Churches, such as the Akathistos, Paraklesis, Evening Prayer, and Prayer for the Faithful Departed (Byzantine), Prayer of Thanksgiving (Armenian), Prayer of the Shrine and the Lakhu Mara (Chaldean), Prayer of Incense and Prayer to Glorify Mary the Mother of God (Coptic), Prayer for the Remission of Sins and Prayer to Follow Christ (Ethiopian), Prayer for the Church, and Prayer of Leave-taking from the Altar (Maronite), and Intercessions for the Faithful Departed (Syrian).
Apart from the recurrences listed in the Enchiridion, special indulgences are granted on occasions of special spiritual significance such as a Jubilee Year or the centenary or similar anniversary of an event such as the apparition of Our Lady at Lourdes or the celebration of a World Youth Day.
Of particular significance is the plenary indulgence attached to the Apostolic Blessing that a priest is to impart when giving the sacraments to a person in danger of death, and which, if no priest is available, the Church grants to any rightly disposed Christian at the moment of death, on condition that that person was accustomed to say some prayers during life. In this case the Church itself makes up for the three conditions normally required for a plenary indulgence: sacramental confession, Eucharistic communion and prayer for the Pope's intentions.
The sixth-century Council of Epaon witnesses to the rise of the practice of replacing severe canonical penances with something new and milder. It became customary to commute penances to less demanding works, such as prayers, alms, fasts and even the payment of fixed sums of money depending on the various kinds of offences (tariff penances). By the tenth century some penances were not replaced but merely reduced in connection with pious donations, pilgrimages and similar meritorious works. Then, in the eleventh and twelfth centuries, the recognition of the value of these works began to become associated not so much with canonical penance but with remission of the temporal punishment due to sin.
The earliest record of a plenary indulgence was Pope Urban II's declaration at the Council of Clermont (1095) that he remitted all penance incurred by crusaders who confessed their sins, considering participation in the crusade equivalent to a complete penance.
Theologians looked to God's mercy, the value of the Church's prayers, and the merits of the saints as the basis on which indulgences could be granted. Around 1230 the Dominican Hugh of St-Cher proposed the idea of a "treasury" at the Church's disposal, consisting of the infinite merits of Christ and the immeasurable abundance of the saints' merits, a thesis that was demonstrated by great scholastics such as Albertus Magnus and Thomas Aquinas and remains the basis for the theological explanation of indulgences.
The later Middle Ages saw the growth of considerable abuses, such as the unrestricted sale of indulgences by professional "pardoners" (quaestores in Latin), who were sent to collect contributions to the project. In many cases the preaching of these, out of ignorance or shrewdness, went far beyond dogmatic truth; some of them even dared to promise that the damned would be released from hell. Permission began to be granted to Catholic kings and princes, particularly on the occasion of Crusades, to retain for themselves a rather considerable part of the alms collected for the gaining of indulgences. The most well-known and debated question is the indulgence granted for building the new St. Peter's Basilica in Rome.
The Fourth Lateran Council (1215) suppressed some abuses connected with indulgences, spelling out, for example, that only a one-year indulgence would be granted for the consecration of churches and no more than a 40-days indulgence for other occasions. But very soon these limits were widely exceeded. In fact, false documents were circulated with indulgences surpassing all bounds: indulgences of hundreds or even thousands of years. In 1392, more than a century before Martin Luther published the 95 Theses, Pope Boniface IX wrote to the Bishop of Ferrara condemning the practice of certain religious who falsely claimed that they were authorized by the pope to forgive all sorts of sins, and exacted money from the simple-minded among the faithful by promising them perpetual happiness in this world and eternal glory in the next.
The false doctrine and scandalous conduct of the "pardoners" were an immediate occasion of the Protestant Reformation. In 1517, Pope Leo X offered indulgences for those who gave alms to rebuild St. Peter's Basilica in Rome. The aggressive marketing practices of Johann Tetzel in promoting this cause provoked Martin Luther to write his Ninety-Five Theses, protesting against what he saw as the purchase and sale of salvation. In Thesis 28 Luther objected to a saying attributed to Tetzel: "As soon as a coin in the coffer rings, a soul from purgatory springs". The Ninety-Five Theses not only denounced such transactions as worldly but denied the Pope's right to grant pardons on God's behalf in the first place: the only thing indulgences guaranteed, Luther said, was an increase in profit and greed, because the pardon of the Church was in God's power alone.
While Luther did not deny the Pope’s right to grant pardons for penance imposed by the Church, he made it clear that preachers who claimed indulgences absolved buyers from all punishments and granted them salvation were in error.
A few years later, in 1567, Pope Pius V cancelled all grants of indulgences involving any fees or other financial transactions. After the Council of Trent, Clement VIII established a commission of Cardinals to deal with indulgences according to the mind of the Council. It continued its work during the pontificate of Paul V and published various bulls and decrees on the matter. But only Clement IX established a true Congregation of Indulgences (and Relics) with a Brief of 6 July 1669. In a Motu Proprio of 28 January 1904, Pius X joined the Congregation of Indulgences with that of Rites, but with the restructuring of the Roman Curia in 1908 all matters regarding indulgences was assigned to the Holy Office. In a Motu Proprio of 25 March 1915, Benedict XV transferred the Holy Office's Section for Indulgences to the Apostolic Penitentiary, but maintained the Holy Office's responsibility for matters regarding the doctrine of indulgences.
Like the Western Church, the Eastern Orthodox Church believes that the only way to be absolved from sins is by the Sacred Mystery of Confession, which in the East is preced by a period of fasting. Because of differences in the underlying doctrine of salvation, indulgences for the remission of temporal punishment of sin do not exist in Eastern Orthodoxy, but until the twentieth century there existed in some places a practice of absolution certificates (συγχωροχάρτια - synchorochartia). While some of these certificates were connected with any patriarch's decrees lifting for the living or the dead some serious ecclesiastical penalty, including excommunication, the Greek Orthodox Patriarch of Jerusalem, with the approval of the Ecumenical Patriarch of Constantinople, had the sole privilege, because of the expense of maintaining the Holy Places and paying the many taxes levied on them, of distributing such documents in large numbers to pilgrims or sending them elsewhere, sometimes with a blank space for the name of the beneficiary, living or dead, an individual or a whole family, for whom the prayers would be read.
Greek Orthodox Patriarch of Jerusalem Dositheos Notaras (1641-1707) wrote: "It is an established custom and ancient tradition, known to all, that the Most Holy Patriarchs give the absolution certificate (συγχωροχάρτιον - synchorochartion) to the faithful people … they have granted them from the beginning and still do.
A Russian Orthodox source says that these certificates were in use among Greek Orthodox until the middle of the twentieth century, and were "certificates which absolved from sins, which anyone could obtain, often for a specified sum of money. The absolution granted by these papers, according to Christos Yannaras, had no connection with any participation of the faithful in the Mystery of Penance, nor in the Mystery of the Eucharist". The same source interprets the Western indulgence also as absolution from sin, not as remission of temporal punishment.