How different from the clear, harmonious, orderly, Greek scheme, is any picture we can form, from such quotations as I have given from their writings, of the alchemists' conception of the world. The Greeks likened their imaginings of nature to the natural facts they observed; the alchemists created an imaginary world after their own likeness. While Christianity was superseding the old religions, and the theological system of the Christian Church was replacing the cosmogonies of the heathen, the contrast between the power of evil and the power of good was more fully realised than in the days of the Greeks; a sharper division was drawn between this world and another world, and that other world was divided into two irreconcilable and absolutely opposite parts. Man came to be regarded as the centre of a tremendous and never-ceasing battle, urged between the powers of good and the powers of evil. The sights and sounds of nature were regarded as the vestments, or the voices, of the unseen combatants. Life was at once very real and the mere shadow of a dream. The conditions were favourable to the growth of magic; for man was regarded as the measure of the universe, the central figure in an awful tragedy. Magic is an attempt, by thinking and speculating about what we consider must be the order of nature, to discover some means of penetrating into the secret life of natural things, of realising the hidden powers and virtues of things, grasping the concealed thread of unity which is supposed to run through all phenomena however seemingly diverse, entering into sympathy with the supposed inner oneness of life, death, the present, past, and future. Magic grows, and gathers strength, when men are sure their theory of the universe must be the one true theory, and they see only through the glasses which their theory supplies. "He who knows himself thoroughly knows God and all the mysteries of His nature," says a modern writer on magic. That saying expresses the fundamental hypothesis, and the method, of all systems of magic and mysticism. Of such systems, alchemy was one. CHAPTER II. A SKETCH OF ALCHEMICAL THEORY. The system which began to be called _alchemy_ in the 6th and 7th centuries of our era had no special name before that time, but was known as _the sacred art, the divine science, the occult science, the art of Hermes_.