Primitive civilizations offer privileged cases, then, because they are simple cases. That is why, in all fields of human activity, the observations of ethnologists have frequently been veritable revelations, which have renewed the study of human institutions. For example, before the middle of the nineteenth century, everybody was convinced that the father was the essential element of the family; no one had dreamed that there could be a family organization of which the paternal authority was not the keystone. But the discovery of Bachofen came and upset this old conception. Up to very recent times it was regarded as evident that the moral and legal relations of kindred were only another aspect of the psychological relations which result from a common descent; Bachofen and his successors, MacLennan, Morgan and many others still laboured under this misunderstanding. But since we have become acquainted with the nature of the primitive clan, we know that, on the contrary, relationships cannot be explained by consanguinity. To return to religions, the study of only the most familiar ones had led men to believe for a long time that the idea of god was characteristic of everything that is religious. Now the religion which we are going to study presently is, in a large part, foreign to all idea of divinity; the forces to which the rites are there addressed are very different from those which occupy the leading place in our modern religions, yet they aid us in understanding these latter forces. So nothing is more unjust than the disdain with which too many historians still regard the work of ethnographers. Indeed, it is certain that ethnology has frequently brought about the most fruitful revolutions in the different branches of sociology. It is for this same reason that the discovery of unicellular beings, of which we just spoke, has transformed the current idea of life. Since in these very simple beings, life is reduced to its essential traits, these are less easily misunderstood.