Christianity constitutes the civilization to which we all in some way belong. Therefore, we can't consider it in the same way as ancient civilizations, which we can only glimpse through the opaque medium of archeology: or in the same way as the civilizations of the non-European world that we strive to understand outside and from afar. This implies a difference in the quality of our judgment, which can be compared to the astronomer's science of a planet and the geographer's knowledge of the earth we live on. For the study of Western civilization, not only do we have a much more abundant reserve of materials than any other, but we also have a more profound and intimate knowledge of it. Western civilization is the atmosphere in which we breathe and the life we live. It is our way of life and that of our ancestors; therefore, we know it not only from documents and monuments but also through our personal experience. Let us imagine for a moment a study of religion that ignored or left aside the accumulated experience of the Christian past; that he used only the distant and partly incomprehensible testimonies drawn from the study of foreign religious traditions; that he resorted to abstract notions about the nature of religion and the conditions of spiritual knowledge. Such a study would be incomplete, inconsistent, and without truth. This shows us the way forward in considering the problem of the relationship between religion and civilization. It is an intricate and pervasive web of connections that unite social life with spiritual beliefs and values, beliefs and values that are recognized by society as the supreme norms of life and the definitive models of individual and social behaviour; because these relationships can only be concretely studied in their total historical reality. The world's great religions are rivers of sacred traditions flowing through the centuries and the changing historical landscape they rinse and fertilize. Still, ordinarily, we cannot go up to the source, lost in the unexplored regions of a distant past. It is rarely possible to find a civilization in which religious evolution can be traced from one end to the other in the whole light of history.