Just as the Theses referred to throw light upon his development,[123] so also, and to an even greater extent, do the Disputations which took place at academic festivals about that same period. In these Disputations propositions drawn up either by himself or by his colleagues, were defended by his pupils under his own direction. They display his theological views as he was wont to vent them at home, and are therefore all the more natural and reliable. Of such Disputations we have that of Bartholomew Bernhardi in 1516 “On the Powers and the Will of Man without Grace”; that of Francis Günther in 1517 “Concerning Grace and Nature,” also entitled “Against the Theology of the Schoolmen,” and the Heidelberg Disputation of 1518, with Leonard Beyer as defendant of twenty-eight philosophical and twelve theological theses. In the latter theses there are also various notes in Luther’s handwriting. Of Luther’s writings, dating from the strenuous year 1518, some of which are in Latin and others in German and which throw some light on his previous development, we may mention in their chronological order: the sermon on “Indulgence and Grace,” the detailed “Resolutions” on the Indulgence Theses, the discourse on Penance, the “Asterisci” against Eck, the pamphlet “Freedom of the Sermon on Indulgence and Grace,” an exposition of Psalm cx., the reply to Prierias, the sermon on the power of excommunication, then the report of his trial at Augsburg and the sermon on the “Threefold Righteousness.” To these we must add his complete edition of “Theologia Deutsch,” an anonymous mystical pamphlet of the fourteenth century a portion of which he had brought out in 1516 with a preface of his own.[124] These are the sources which Luther himself has left behind him and from which the inner history of his apostasy and of his new theology must principally be taken. The further evidence derivable from his later works, his sermons, letters and Table-Talk, will be dealt with in due course. * * * * *