Others give us the religious interpretation of history. They tell us of those epochs when great masses of men, impelled by a wave of religious enthusiasm, moved to fiery zeal, their imaginations touched, their moral sense deeply stirred, have become knights of the faith, missionaries armed with fire and sword; the scourges of God. Such causes impelled the Saracenic invasion of Africa and Europe, and the Crusades. Other historians have studied the great migratory movements that have swept vast bodies of men away from their native environments, and precipitated new elements into history. Such were the migrations of the tribes of Northern Europe, and of the Asiatic hordes, which were a powerful element in the overturn of the Roman Empire. In late years there has been an increasing interest in the biographies of the great men who have moved the world. No view of history is more interesting than this study of personalities. It has sometimes been pushed to an absurd extent, in the attempt to reverse historical verdicts, to rehabilitate tarnished reputations, and in the exaggeration of hero-worship. The relation of great men to their times has been a fascinating theme for the historian to dwell upon in every age. All these, and many more inquiries, are worthy of the most painstaking study. We cannot know too much about them. They are all a part of "the moulding together the great mysterious incorporation of the human race." But the moral lesson of history is larger than any exceptional episodes.