historical and ethnological observation alone can reveal that to us. But even if this cardinal conception is obtained by a different process than that of Descartes, it remains true that it is destined to have a considerable influence on the whole series of propositions which the science establishes. Biological evolution has been conceived quite differently ever since it has been known that monocellular beings do exist. In the same way, the arrangement of religious facts is explained quite differently, according as we put naturism, animism or some other religious form at the beginning of the evolution. Even the most specialized scholars, if they are unwilling to confine themselves to a task of pure erudition, and if they desire to interpret the facts which they analyse, are obliged to choose one of these hypotheses, and make it their starting-point. Whether they desire it or not, the questions which they raise necessarily take the following form: how has naturism or animism been led to take this particular form, here or there, or to enrich itself or impoverish itself in such and such a fashion? Since it is impossible to avoid taking sides on this initial problem, and since the solution given is destined to affect the whole science, it must be attacked at the outset: that is what we propose to do. Besides this, outside of these indirect reactions, the study of primitive religions has of itself an immediate interest which is of primary importance. If it is useful to know what a certain particular religion consists in, it is still more important to know what religion in general is. This is the problem which has aroused the interest of philosophers in all times; and not without reason, for it is of interest to all humanity. Unfortunately, the method which they generally employ is purely dialectic: they confine themselves to analysing the idea which they make for themselves of religion, except as they illustrate the results of this mental analysis by examples borrowed from the religions which best realize their ideal. But even if this method ought to be abandoned, the problem remains intact, and the great service of philosophy is to have prevented its being suppressed by the disdain of scholars. Now it is possible to attack it in a different way. Since all religions can be compared to each other, and since all are species of the same class, there are necessarily many elements which are common to all. We do not mean to speak simply of the outward and visible characteristics which they all have equally, and which make it possible to give them a provisional definition from the very outset of our researches; the discovery of these apparent signs is relatively easy, for the observation which it demands does not go beneath the surface of things. But these external resemblances suppose others which are profound. At the foundation of all systems of beliefs and of all cults there ought necessarily to be a certain number of fundamental representations or