From 'The Roots of the Reformation' by Karl Adam
Omne malum a clero--every evil comes from the clergy. As early as 1245 at the Council of Lyons, Pope Innocent IV had called the sins of the higher and lower clergy one of the five wounds in the Body of the Church, and at the second Council of Lyons in 1274 Gregory X declared that the wickedness of many prelates was the cause of the ruin of the whole world (cf. Bihlmeyer, vol. ii, p. 336).
In this waste of clerical corruption it was impossible for the spirit of our Lord to penetrate into the people, take root there and bring true religion to flower. Since there was at this time no catechism of infants, the sermons on Sundays and feast-days were the chief sources from which the laity drew their religious education. And these sources were often choked up. Since at this time, moreover, as during the whole of the Middle Ages, Communion was very infrequent outside the ranks of the mystics, there was no sacramental impulse towards an interiorizing and deepening of religion. So the attention of the faithful was directed towards externals. Religion was materialized. Pious interest was focused more on the "holy things"--relics--than on the sacraments, more on pilgrimages and flagellations than on attending the services of the Church, and most of all on indulgences.
The cult of relics and indulgences had grown to gigantic proportions since Leo X had attached indulgences of a thousand, ten thousand and a hundred thousand years to the veneration of relics. Erasmus criticized this kind of piety in the bitter words: "We kiss the shoes of the saints and their dirty kerchiefs while we leave their writings, their holiest and truest relics, to lie unread" (Lortz, vol. i, p. 108). Frederick the Wise, the famous protector of Luther, had built up his treasury of relics in the Castle Church at Wittenburg to 18,885 fragments. Anyone who believed in and venerated them could gain indulgences amounting to two million years. When Boniface IX made of ecclesiastical indulgences what looked like a commercial traffic, even secular princes and cities became eager to take part in the distribution of them, so as to assure for themselves a generous share of the inflowing money.
From the middle of the fifteenth century the Popes began to distribute indulgences for the dead. The Legate Peraudi, in connection with an indulgence granted by Pope Sixtus IV to Louis XI for the whole of France, announces that the indulgence could be made certainly effective for any soul in purgatory, even if the person gaining it were in a state of mortal sin, so long as the indulgenced work (i.e., money payment) were performed. Pope Sixtus IV did indeed correct his legate's declaration to the extent of saying that the application of the indulgence to the dead could only be a matter of petition, not of certainty. But Peraudi's other statement--that the indulgence could be gained for the dead by people living in mortal sin--was never censured. In the prevailing low state of clerical education, preachers of the indulgence (such as the Dominican Tetzel for instance) eagerly seized on Peraudi's pronouncement, so that many preachers really did adopt as their favourite tag: "Your cash no sooner clinks in the bowl than out of purgatory jumps the soul." Some of the papal decrees themselves were in great measure responsible for this crude interpretation of indulgences. They employed a misleading formula current from the thirteenth century onwards which spoke of a remissio a poena et culpa (remission of pain and guilt) or even of a remissio peccatorum (remission of sins), whereas an indulgence is not concerned with the forgiveness of the guilt of sin, nor with the remission of eternal punishment, but only with the remission of temporal punishment, that is, a mitigation or shortening of that penitential suffering which the sinner must undergo either here or in purgatory.