DISTRIBUTION

by Alfred Russel Wallace The ninth edition (187589) article Distribution describes patterns in the geography of life, both the observed areas occupied by the Earth's organisms and the changes in their spatial arrangement over time. Wallace, by the 1870s an established natural historian and geographer, wrote the first part of this article, on the Distribution of Animals. Extracts from his essay are reproduced below. Wallace's great theme is the close relationship between distribution and evolution. Once the theory of the gradual development of organic forms is accepted, he argues, then the time of a living creature's appearance, its place of origin, and the areas it now occupies become essential portions of the history of the universe. He begins his article with a statement of this general theme and a synopsis of the six major zoological regions of the world. clasbody, distribution1 Wallace goes on to describe each zoological region in detail. The descriptions of the Australian Region (where life forms are so different that the zoologist seems to have got into a new world) and the Neotropical Region (in some respects the richest zoological region on the globe) are particularly vivid, perhaps because the author spent more than a decade of his life personally exploring them. clasbody, distribution2 Turning from the distribution of animal life in space, Wallace considers the ever-changing panorama of life through time. The fossil record, he argues, leads one inevitably to conclude that lifeand the Earth itselfhave evolved over time spans of almost unimaginable vastness. clasbody, distribution3 also called Distribution Of Terms, in syllogistics, the application of a term of a proposition to the entire class that the term denotes. A term is said to be distributed in a given proposition if that proposition implies all other propositions that differ from it only in having, in place of the original term, any other term whose extension is a part of that of the original termi.e., if, and only if, the term as it is used in that occurrence covers all the members of the class that it denotes. Thus, in a proposition of the form No S is P, both the subject and the predicate are distributed. In the form Some S is P, neither S nor P is distributed. In Every S is P, S is distributed, but P is not. Lastly, in Some S is not P, S is not distributed, but P is. Briefly, only universal propositions distribute the subject term (S), and only negative propositions distribute their predicate (P). Naturally, singular terms (including proper names used as singular terms) are always distributed, for they refer only to one object and cannot refer to fewer. The importance of distribution lies in its being a principle of formal inference that no term may be distributed in the conclusion unless it was distributed in the premises.