The present volume is merely an expansion of the corresponding chapter in the first edition of _The Golden Bough_. It treats of the principles of taboo in their special application to sacred personages, such as kings and priests, who are the proper theme of the book. It does not profess to handle the subject as a whole, to pursue it into all its ramifications, to trace the manifold influences which systems of this sort have exerted in moulding the multitudinous forms of human society. A treatise which should adequately discuss these topics would far exceed the limits which I have prescribed for myself in _The Golden Bough_. For example, I have barely touched in passing on the part which these superstitions have played in shaping the moral ideas and directing the moral practice of mankind, a profound subject fraught perhaps with momentous issues for the time when men shall seriously set themselves to revise their ethical code in the light of its origin. For that the ethical like the legal code of a people stands in need of constant revision will hardly be disputed by any attentive and dispassionate observer. The old view that the principles of right and wrong are immutable and eternal is no longer tenable. The moral world is as little exempt as the physical world from the law of ceaseless change, of perpetual flux. Contemplate the diversities, the inconsistencies, the contradictions of the ethical ideas and the ethical practice, not merely of different peoples in different countries, but of the same people in the same country in different ages, then say whether the foundations of morality are eternally fixed and unchanging. If they seem so to us, as they have probably seemed to men in all ages who did not extend their views beyond the narrow limits of their time and country, it is in all likelihood merely because the rate of change is commonly so slow that it is imperceptible at any moment and can only be detected by a comparison of accurate observations extending over long periods of time. Such a comparison, could we make it, would probably convince us that if we speak of the moral law as immutable and eternal, it can only be in the relative or figurative sense in which we apply the same words to the outlines of the great mountains, by comparison with the short-lived generations of men. The mountains, too, are passing away, though we do not see it; nothing is stable and abiding under or above the sun. We can as little arrest the process of moral evolution as we can stay the sweep of the tides or the courses of the stars.