But our study is not of interest merely for the science of religion. In fact, every religion has one side by which it overlaps the circle of properly religious ideas, and there, the study of religious phenomena gives a means of renewing the problems which, up to the present, have only been discussed among philosophers.
For a long time it has been known that the first systems of representations with which men have pictured to themselves the world and themselves were of religious origin. There is no religion that is not a cosmology at the same time that it is a speculation upon divine things. If philosophy and the sciences were born of religion, it is because religion began by taking the place of the sciences and philosophy. But it has been less frequently noticed that religion has not confined itself to enriching the human intellect, formed beforehand, with a certain number of ideas; it has contributed to forming the intellect itself. Men owe to it not only a good part of the substance of their knowledge, but also the form in which this knowledge has been elaborated.
At the roots of all our judgments there are a certain number of essential ideas which dominate all our intellectual life; they are what philosophers since Aristotle have called the categories of the understanding: ideas of time, space,[4] class, number, cause, substance, personality, etc. They correspond to the most universal properties of things. They are like the solid frame which encloses all thought; this does not seem to be able to liberate itself from them without destroying itself, for it seems that we cannot think of objects that are not in time and space, which have no number, etc. Other ideas are contingent and unsteady; we can conceive of their being unknown to a man, a society or an epoch; but these others appear to be nearly inseparable from the normal working of the intellect. They are like the framework of the intelligence. Now when primitive religious beliefs are systematically analysed, the principal categories are naturally found. They are born in religion and of religion; they are a product of religious thought. This is a statement that we are going to have occasion to make many times in the course of this work.