Physical geography he viewed as a summary of nature, the basis not only of history but also of "all the other possible geographies," of which he enumerates five, viz. (1) _Mathematical geography_, which deals with the form, size and movements of the earth and its place in the solar system; (2) _Moral geography_, or an account of the different customs and characters of mankind according to the region they inhabit; (3) _Political geography_, the divisions according to their organized governments; (4) _Mercantile geography_, dealing with the trade in the surplus products of countries; (5) _Theological geography_, or the distribution of religions. Here there is a clear and formal statement of the interaction and causal relation of all the phenomena of distribution on the earth's surface, including the influence of physical geography upon the various activities of mankind from the lowest to the highest. Notwithstanding the form of this classification, Kant himself treats mathematical geography as preliminary to, and therefore not dependent on, physical geography. Physical geography itself is divided into two parts: a general, which has to do with the earth and all that belongs to it--water, air and land; and a particular, which deals with special products of the earth--mankind, animals, plants and minerals. Particular importance is given to the vertical relief of the land, on which the various branches of human geography are shown to depend. Humboldt.