These theses, notwithstanding of their great boldness, still bespeak the monk, who refuses to allow a single doubt as to the authority of the See of Rome. But in attacking the doctrine of indulgences, Luther had, without perceiving it, assailed several errors, the exposure of which could not be agreeable to the pope, seeing that they tended, sooner or later, to bring his supremacy in question. Luther, at the time, did not see so far; but he felt all the boldness of the step which he had just taken, and, consequently, thought himself bound to temper it in so far as was consistent with the respect due to truth. He, accordingly, presented his theses only as doubtful propositions on which he was anxious for the views of the learned; and, conformably to the established custom, annexed to them a solemn protestation, declaring that he wished not to say or affirm any thing not founded on Holy Scripture, the Fathers of the Church, and the rights and decretals of the See of Rome. Often, in the sequel, on contemplating the immense and unlooked-for consequences of this courageous attack, Luther was astonished at himself, and could not understand how he had ventured upon it. An invisible hand, mightier than his own, held the leading reins, and pushed him into a path which he knew not, and from the difficulties of which he would, perhaps, have recoiled, if he had known them, and been advancing alone and of himself. "I engaged in this dispute," says he, "without premeditated purpose, without knowing it or wishing it; and was taken quite unprepared. For the truth of this I appeal to the Searcher of hearts."[363] [363] "Casu enim, non voluntate nec studio, in has turbas incidi, Deum ipsum testor." (Luth. Op. Lat. in Præf.) For I got involved in these disturbances by accident, not by will or zeal. God is my witness. Luther had become acquainted with the source of these abuses. He had received a little book, ornamented with the arms of the Archbishop of Mentz and Magdeburg, and containing the regulations to be observed in the sale of indulgences. It was this young prelate, therefore, this accomplished prince, who had prescribed, or at least sanctioned, all this quackery. In him Luther only sees a superior to whom he owes fear and reverence;[364] and wishing not to beat the air, but to address those entrusted with the government of the Church, he sends him a letter, distinguished at once by its frankness and humility. Luther wrote this letter to Albert the same day on which he put up his theses. [364] "Domino suo et pastori in Christo venerabiliter metuendo." To his reverently to be feared Lord and pastor in Christ. (Address of the letter, Ep. i, p. 68.)