First published in 1968. It can hardly be denied that the men who have most changed history have been the great religious leaders. Among the great prophets, and, with the possible exception of Calvin, the last of world-wide importance, Martin Luther has taken his place. His career marks the beginning of the present epoch, for it is safe to say that every man in western Europe and in America is leading a different life to-day from what he would have led and is another person altogether from what he would have been, had Martin Luther not lived. Granting, as axiomatic, that essential factors of the movement are to be found in the social, political, and cultural conditions of the age, and in the work of predecessors and followers, in short, in the environment which alone made Luther's lifework possible, there must still remain a very large element due directly and solely to his personality. The present work aims to explain that personality; to show him in the setting of his age; to indicate what part of his work is to be attributed to his inheritance and to the events of the time, but especially to reveal that part of the man which seems, at least, to be explicable by neither heredity nor environment, and to be more important than either, the character, or individuality.