Regarded from the point of view of the student of intellectual development, this conflict of two thousand years has the fascination of a great drama of which the protagonist is the mind struggling to free the spirit from its subjection to the evil aspects of the imagination. Great thinkers in the field of science, philosophy, and religion are the _dramatis personæ_, and in the onward rush of this world-drama the sufferings of those who have fallen by the way seem insignificant. But when the student of history takes his more intimate survey of the purely human aspects of the struggle, heartrending, indeed, become the tragedies resulting from the exercise of human bigotry and stupidity. Indignation and sorrow take possession of us when we think upon such a spectacle as that of Roger Bacon, making ready to perform a few scientific experiments before a small audience at Oxford, confronted by an uproar in which monks, fellows, and students rushed about, their garments streaming in the wind, crying out, "Down with the magician!" And this was only the beginning of a persecution which ended in his teaching being solemnly condemned by the authorities of the Franciscan order and himself thrown for fourteen years into prison, whence he issued an old and broken man of eighty. More barbarous still was the treatment of Giordano Bruno, a strange sort of man who developed his philosophy in about twenty-five works, some prose, some poetry, some dialogues, some comedies, with such enticing titles as "The Book of the Great Key," "The Explanation of the Thirty Seals," "The Expulsion of the Triumphant Beast," "The Threefold Minimum," "The Composition of Images," "The Innumerable, the Immense and the Unfigurable." His utterances were vague, especially to the intellects of his time, yet not so vague that theology, whether Catholic or Calvinistic, did not at once take fright. He held that the investigation of nature in the unbiased light of reason is our only guide to truth. He rejected antiquity, tradition, faith, and authority; he exclaimed, "Let us begin by doubt. Let us doubt till we know." Acting upon these principles, he began to unfold again that current of Greek thought which the system imposed by the Church had intercepted for more than a thousand years, and arrived at a conception of evolution prefiguring the modern theories. He conceived the law of the universe to be unceasing change. "Each individual," he declared, "is the resultant of innumerable individuals; each species is the starting point for the next." Furthermore, he maintained that the perfecting of the individual soul is the aim of all progress.