ABSTRACT
As long as man's knowledge of nature is limited to what he can observe in his immediate vicinity, he has little difficulty in controlling the objects of his knowledge, but when his range of vision widens, there arises the irresistible need for combining the individual objects that have been observed under general expressions, which serve to fix the knowledge of them and to impart it to others, "since no language would suffice to denote everything individually, and since in a language which did so, no understanding, no common knowledge, nor retention of such an infinity of terms would be possible" (F. A. Lange). Those categories in which natural objects are thus grouped by the most primitive peoples, out of sheer practical necessity, are naturally based on such qualities in animals and plants as well as the inanimate things that are observed as are easily comprehended, striking to the eye, and of special importance to the observers, and such terms are also used and invented even today among civilized peoples by all those who are concerned with nature in a purely practical way. On the other hand, a grouping of natural objects based on scientific principles has taken a long time to develop. In this respect the ancient Greek natural philosophy was content with the primitive popular nomenclature. Practically the first to devote scientific study to these groupings were, as far as we know, Plato and Aristotle. From Plato originates grouping in species and genera — that is to say, laterally arranged and superordinated terms — and his school still further extended this grouping of terms: the dichotomical determination-tables which even today play such an important part in plant and animal systematization originate from his school. But the further this grouping of terms went on, the more abstract became the result; the higher one came in the series of terms arranged one above another, the further away has one come from the things which one started from. This is a fact which the biological systematicians have not always realized; the practical advantage of systematic categories has led to the zoologist's and the botanist's forgetting how artificial their system has really become.
