But if the categories originally only translate social states, does it not follow that they can be applied to the rest of nature only as metaphors? If they were made merely to express social conditions, it seems as though they could not be extended to other realms except in this sense. Thus in so far as they aid us in thinking of the physical or biological world, they have only the value of artificial symbols, useful practically perhaps, but having no connection with reality. Thus we come back, by a different road, to nominalism and empiricism. But when we interpret a sociological theory of knowledge in this way, we forget that even if society is a specific reality it is not an empire within an empire; it is a part of nature, and indeed its highest representation. The social realm is a natural realm which differs from the others only by a greater complexity. Now it is impossible that nature should differ radically from itself in the one case and the other in regard to that which is most essential. The fundamental relations that exist between things--just that which it is the function of the categories to express--cannot be essentially dissimilar in the different realms. If, for reasons which we shall discuss later,[21] they are more clearly disengaged in the social world, it is nevertheless impossible that they should not be found elsewhere, though in less pronounced forms. Society makes them more manifest but it does not have a monopoly upon them. That is why ideas which have been elaborated on the model of social things can aid us in thinking of another department of nature. It is at least true that if these ideas play the rôle of symbols when they are thus turned aside from their original signification, they are well-founded symbols. If a sort of artificiality enters into them from the mere fact that they are constructed concepts, it is an artificiality which follows nature very closely and which is constantly approaching it still more closely.[22] From the fact that the ideas of time, space, class, cause or personality are constructed out of social elements, it is not necessary to conclude that they are devoid of all objective value. On the contrary, their social origin rather leads to the belief that they are not without foundation in the nature of things.[23]