We have now carefully considered the acts and dynamic activity of human thought. We have seen in what animal and human perception consists, and how it acts; how the subjects developed in our imagination are gradually united in specific forms or types, and are arranged in a system, whence follow the first symbolic representations of science. But our task is not yet accomplished, since much more is needed to display all that this fact involves, so that we may fully understand the inward evolution of myth and science in history and in our race, and not merely in the individual man. The faculty and its effects, which could primarily be reduced to this unique and indivisible fact, do not exclusively belong to primordial ages, but go on through all time, our own included, while assuming divers forms and fresh aspects as the faculty of the intellect becomes more developed. It is an indisputable truth that the influence of myth on thought and fancy, a survival from prehistoric ages, still prevails among the common people both in town and country, among those who are uncultivated, and even in the higher classes conventionally called good society. It is more difficult to trace the occasional existence of the same influence among those who think rationally and investigate the laws of the universe while acquainted with the earlier mythical process; and yet, as we shall show, the greatest and most able men are not unfettered by it. Myth has hitherto been regarded as a secondary and fanciful product of the psychical human faculty, due to extrinsic impulses, rather than as the primitive and intrinsic necessity of the intelligence--a necessity which has its roots in animal intelligence itself; and the unique fact which generates both myth and science has not been ascertained. If this fact and law had been discovered before, we should have more readily understood religions, philosophic systems, and the successive forms of science, and pure reason would have made more rapid progress. Our theory, besides giving a rational explanation of the different forms assumed by thought in the course of its historic evolution, will, I hope, also account for many psychological phenomena which have hitherto been imperfectly understood, such as dreams, hallucinations, the aberrations of insanity, and the like. The primitive fact and its effects reappear in these conditions, and this influence is persistent and enters into all our acts, conscious or unconscious, voluntary or involuntary.