The popes, in their pecuniary straits, perceiving how lucrative the practice might become, deprived the bishops of the right of making such sales, and appropriated it to themselves, establishing agencies, chiefly among the mendicant orders, for the traffic.

Among these orders there was a sharp competition, each boasting of the superior value of its indulgences through its greater influence at the court of heaven, its familiar connection with the Virgin Mary and the saints in glory.

Even against Luther himself, who had been an Augustinian monk, a calumny was circulated that he was first alienated from the Church by a traffic of this kind having been conferred on the Dominicans, instead of on his own order, at the time when Leo X.was raising funds by this means for building St.Peter's, at Rome, A.D.1517.

and there is reason to think that Leo himself, in the earlier stages of the Reformation, attached weight to that allegation.
Indulgences were thus the immediate inciting cause of the Reformation, but very soon there came into light the real principle that was animating the controversy.

It lay in the question, Does the Bible owe its authenticity to the Church?
or does the Church owe her authenticity to the Bible?
Where is the criterion of truth?
It is not necessary for me here to relate the well known particulars of that controversy, the desolating wars and scenes of blood to which it gave rise: how Luther posted on the door of the cathedral of Wittemberg ninety-five theses, and was summoned to Rome to answer for his offense; how he appealed from the pope, ill-informed at the time, to the pope when he should have been better instructed; how he was condemned as a heretic, and thereupon appealed to a general council; how, through the disputes about purgatory, transubstantiation, auricular confession, absolution, the fundamental idea which lay at the bottom of the whole movement came into relief, the right of individual judgment; how Luther was now excommunicated, A.D.1520, and in defiance burnt the bull of excommunication and the volumes of the canon law, which he denounced as aiming at the subversion of all civil government, and the exaltation of the papacy; how by this skillful manoeuvre he brought over many of the German princes to his views; how, summoned before the Imperial Diet at Worms, he refused to retract, and, while he was bidden in the castle of Wartburg, his doctrines were spreading, and a reformation under Zwingli broke out in Switzerland; how the principle of sectarian decomposition embedded in the movement gave rise to rivalries and dissensions between the Germans and the Swiss, and even divided the latter among themselves under the leadership of Zwingli and of Calvin; how the Conference of Marburg, the Diet of Spires, and that at Augsburg, failed to compose the troubles, and eventually the German Reformation assumed a political organization at Smalcalde.