The present work aims to set before the public the history, as told by the participants and eye-witnesses themselves in all the unreserve of private correspondence, of the most momentous crisis in the annals of Europe. It is impossible here to appreciate the importance of the Reformation; I have done it, partially, elsewhere, and hope to return to it in future. Suffice it to say that the revolution which goes by this name wrought an upheaval in the political, social and religious structure of Europe and prepared the ground for our modern civilizaiton. Every element of the movement is reflected in these letters: the return to the Bible, the revolt from ecclesiastical abuse and from papal authority, the economic and social reform, the growing nationalism and awakening subjectivism. The launching of the 'Ninety-five Theses' is described and their working on the minds of men portrayed; the summons of Luther before his ecclesiastical superiors first at Heidelberg and then at Augsburg, the great debate with Eck at Leipsic, the trumpet call to spiritual emancipation in the pamphlets of 1520, the preparation of the bull of excommunication and the burning of the same, and finally, as a fitting climax, the memorable appearance of Luther before the Emperor and Diet at Worms, are all set before our eyes. --from the Preface