The difference in the mode of thought of primitive man and that of civilized man seems to consist largely in the difference of character of the traditional material with which the new perception associates itself. The instruction given to the child of primitive man is not based on centuries of experimentation, but consists of the crude experience of generations. When a new experience enters the mind of primitive man, the same process which we observe among civilized man brings about an entirely different series of associations, and therefore results in a different type of explanation. A sudden explosion will associate itself in his mind, perhaps, with tales which he has heard in regard to the mythical history of the world, and consequently will be accompanied by superstitious fear. When we recognize that neither among civilized men nor among primitive men the average individual carries to completion the attempt at causal explanation of phenomena, but carries it only so far as to amalgamate it with other previously known facts, we recognize that the result of the whole process depends entirely upon the character of the traditional material. Herein lies the immense importance of folk-lore in determining the mode of thought. Herein lies particularly the enormous influence of current philosophic opinion upon the masses of the people, and herein lies the influence of the dominant scientific theory upon the character of scientific work. It would be vain to try to understand the development of modern science without an intelligent understanding of modern philosophy; it would be vain to try to understand the history of mediæval science without a knowledge of mediæval theology; and so it is vain to try to understand primitive science without an intelligent knowledge of primitive mythology. “Mythology,” “theology,” and “philosophy” are different terms for the same influences which shape the current of human thought, and which determine the character of the attempts of man to explain the phenomena of nature. To primitive man,—who has been taught to consider the heavenly orbs as animate beings; who sees in every animal a being more powerful than man; to whom the mountains, trees, and stones are endowed with life,—explanations of phenomena will suggest themselves entirely different from those to which we are accustomed, since we base our conclusions upon the existence of matter and force as bringing about the observed results. If we should not consider it possible to explain the whole range of phenomena as the result of matter and force alone, all our explanations of natural phenomena would take a different aspect.