It may perhaps be asked, Why should those differences exist? And if the question should be put, I am inclined to say that to give the answer is beyond the scope of the applied science of religion. The method of comparison assumes that the differences do exist, and it cannot begin to be employed unless and until they exist. They are and must be taken for granted, at any rate by the applied science of religion, and if the method of comparison is to be set to work. Indeed, if we may take the principle of evolution to be the differentiation of the homogeneous, we may go further and say that the whole theory of evolution, and not merely a particular historic science, such as the science of religion, {24} postulates differentiation and the principle of difference, and does not explain it,--evolution cannot start, the homogeneous cannot be other than homogeneous, until the principle of difference and the power of differentiation is assumed. That the science of religion at the end leaves untouched those differences between religions which it recognised at the beginning, is a point on which I insisted, as against those who unwarrantably proclaim the science to have demonstrated that all religions alike are barbarisms or survivals of barbarism. It is well, therefore, to bear that fact in mind when attempts are made to explain the existence of the differences by postulating a period when they were non-existent. That postulate may take form in the supposition that originally the true religion alone existed, and that the differences arose later. That is a supposition which has been made by more than one people, and in more ages than one. It carries with it the consequence that the history--it would be difficult to call it the evolution and impossible to call it the progress--of religion has been one of degradation generally. Owing, however, to the far-reaching and deep-penetrating influence of the theory of evolution, it has of late grown {25} customary to assume that the movement, the course of religious history, has been in the opposite direction; and that it has moved upwards from the lowest forms of religion known to us, or from some form analogous to the lowest known forms, through the higher to the highest. This second theory, however different in its arrangement of the facts from the Golden Age theory first alluded to, is still fundamentally in agreement with it, inasmuch as it also assumes that the differences exhibited later in the history of religion at first were non-existent. Both theories assume the existence of the originally homogeneous, but they disagree as to the nature of the differences which supervened, and also as to the nature of the originally homogeneous.