Chapter I
Sin, penance and the treasury of merit
To understand indulgences, one must start with the medieval theology of penance. In Catholic teaching, a sinner who repents and confesses is forgiven the guilt of sin and freed from eternal punishment. But a debt of temporal punishment remains, to be paid through acts of penance in this life or through purification in purgatory after death. In the early Church, penances were long and public, sometimes lasting years. Over time the Church allowed them to be commuted into other pious works, such as prayers, pilgrimages, fasting or gifts to the poor.
An indulgence was the Church’s declaration that part or all of this temporal punishment was remitted. A partial indulgence was measured in days or years, corresponding to the old penitential periods; a plenary indulgence remitted the whole. The first great plenary indulgence was offered in 1095, when Pope Urban II promised that those who went on crusade with pure intention would have their penance counted as fulfilled. In 1300 Boniface VIII extended a plenary indulgence to pilgrims who visited Rome during the first Jubilee year.
Theologians explained the source of this power with the idea of the treasury of merit. Christ’s sacrifice, and the good works of the Virgin Mary and the saints, had produced a superabundance of merit, more than was needed for their own salvation. The Church, holding the keys given to St Peter, could distribute from this treasury to the faithful. Pope Clement VI set out the doctrine in his bull Unigenitus in 1343. In 1476 Sixtus IV declared that the living could gain indulgences for souls already in purgatory, by way of intercession.