It is also to be borne in mind that a classification is a system whose parts are arranged according to a hierarchy. There are dominating members and others which are subordinate to the first; species and their distinctive properties depend upon classes and the attributes which characterize them; again, the different species of a single class are conceived as all placed on the same level in regard to each other. Does someone prefer to regard them from the point of view of the understanding? Then he represents things to himself in an inverse order: he puts at the top the species that are the most particularized and the richest in reality, while the types that are most general and the poorest in qualities are at the bottom. Nevertheless, all are represented in a hierarchic form. And we must be careful not to believe that the expression has only a metaphorical sense here: there are really relations of subordination and co-ordination, the establishment of which is the object of all classification, and men would never have thought of arranging their knowledge in this way if they had not known beforehand what a hierarchy was. But neither the spectacle of physical nature nor the mechanism of mental associations could furnish them with this knowledge. The hierarchy is exclusively a social affair. It is only in society that there are superiors, inferiors and equals. Consequently, even if the facts were not enough to prove it, the mere analysis of these ideas would reveal their origin. We have taken them from society, and projected them into our conceptions of the world. It is society that has furnished the outlines which logical thought has filled in. III But these primitive classifications have a no less direct interest for the origins of religious thought.