Ur 



. 223. THEORY OF THE SYSTEM. 329 



. 223. PRINCIPLE OF CLASSIFICATION. 



The principle of classification in Natural History 

 is the Natural-Historical Resemblance. 



Several bodies are similar, or resemble each other, which 

 approximate more or less in their properties ; and this re- 

 semblance is the greater, the higher we find the degree of 

 approximation. 



In Geometry, similarity consists in the equality of the 

 relations among homogeneous quantities, and allows of 

 no variation. The idea of similarity in Natural History 

 is not so simple ; it cannot be expressed by a single ratio, 

 because here a great many properties must be taken into 

 consideration. It receives a certain latitude, in which 

 there may occur some variation. This, however, has no 

 prejudicial influence, either upon its evidence, or upon 

 its applicability. On the contrary, if we apply this idea 

 of similarity to nature, we find that only owing to the greater 

 extent ascribed to it in a natural-historical consideration, 

 it is capable of being the principle of classification in Natural 

 History, 



It is not difficult to decide the question, whether or not 

 the natural-historical resemblance should be fixed upon as 

 the principle of classification in Natural History. In every 

 science the classification must rest upon such relations as are 

 objects of the science, and therefore it must represent nature 

 according to the image expressed by these relations. Natu- 

 ral History refers to none but the natural-historical proper- 

 ties ; hence the approximation of heterogeneous bodies in 

 these properties, or the natural-historical resemblance, is the 

 only relation expressed among or by means of the produc- 

 tions of nature. For this reason Natural History is forced, 

 not only to apply this resemblance as its principle of classifi- 

 cation, but also carefully to explain and illustrate it, in order 

 to render the classification a true and sufficient representa- 

 tion of nature. In this respect a classification may be called 

 natural. The organic kingdoms of nature have always had 



