When, however, towards the end of the year, Eck published the theses which he intended to defend, Luther found with astonishment that they dealt with cardinal points of doctrine, which he himself, rather than Carlstadt, had maintained, and that Carlstadt was expressly designated the 'champion of Luther.' Only one of these theses related to a doctrine specially defended by Carlstadt, namely, that of the subjection of the will in sinful man. Among the other points noticed was the denial of the primacy of the Romish Church during the first few centuries after Christ. Eck had extracted this from Luther's recent publications; so far as Carlstadt was concerned, he could not have read or heard a word of such a statement.
Luther fired up. In a public letter addressed to Carlstadt he observed that Eck had let loose against him, in reality, the frogs or flies intended for Carlstadt, and he challenged Eck himself. He would not reproach him for having so maliciously, uncourteously, and in an untheological manner charged Carlstadt with doctrines to which he was a stranger; he would not complain of being drawn himself again into the contest by a piece of base flattery on Eck's part towards the Pope; he would merely show that his crafty wiles were well understood, and he wished to exhort him in a friendly spirit, for the future, if only for his own reputation, to be a little more sensible in his stratagems. Eck might then gird his sword upon his thigh, and add a Saxon triumph to the others of which he boasted, and so at length rest on his laurels. Let him bring forth to the world what he was in labour of; let him disgorge what had long been lying heavy on his stomach, and bring his vainglorious menaces at length to an end.
Luther was anxious, indeed, apart from this special reason, to be allowed to defend in a public disputation the truth for which he was called a heretic; he had made this proposal in vain to the legate at Augsburg. He now demanded to be admitted to the lists at Leipzig. He wished in particular, to take up the contest, openly and decisively, about the Papal primacy.
His friends just on this point grew anxious about him. But he prepared his weapons with great diligence, studying thoroughly the ecclesiastical law-books and the history of ecclesiastical law, with which until now he had never occupied himself so much. Herein he found his own conclusions fully confirmed. Nay, he found that the tyrannical pretensions of the Pope, even if more than a thousand years old, derived their sole and ultimate authority from the Papal decretals of the last four centuries. Arrayed against the theory of that primacy were the history of the previous centuries, the authority of the Council of Nice in 325, and the express declaration of Scripture. This he stated now in a thesis, and announced his opinion in print.