718 THE PRINCIPLES OF SCIENCE. [CHAP. 



Society is doing great service in publishing a complete 

 catalogue of memoirs upon physical science. The time 

 will perhaps come when our views upon this subject will 

 be extended, and either Government or some public society 

 will undertake the systematic cataloguing and indexing of 

 masses of historical and scientific information which are 

 now almost closed against inquiry. 



Classification in the Biological Sciences. 



The great generalisations established in the works of 

 Herbert Spencer and Charles Darwin have thrown much 

 light upon other sciences, and have removed several 

 difficulties out of the way of the logician. The subject of 

 classification has long been studied in almost exclusive 

 reference to the arrangement of animals and plants. 

 Systematic botany and zoology have been commonly 

 known as the Classificatory Sciences, and scientific men 

 seemed to suppose that the methods of arrangement, 

 which were suitable for living creatures, must be the best 

 for all other classes of objects. Several mineralogists, 

 especially Mohs, have attempted to arrange minerals in 

 genera and species, just as if they had been animals 

 capable of reproducing their kind with variations. This 

 confusion of ideas between the relationship of living forms 

 and the logical relationship of things in general prevailed 

 from the earliest times, as manifested in the etymology of 

 words. We familiarly speak of a kind of things meaning 

 a class of things, and the kind consists of those things 

 which are akin, or come of the same race. When Socrates 

 and his followers wanted a name for a class regarded in a 

 philosophical light, they adopted the analogy in question, 

 and called it a 761/05, or race, the lootyev- being connected 

 with the notion of generation. 



So long as species of plants and animals were believed 

 to proceed from distinct acts of Creation, there was no 

 apparent reason why methods of classification suitable to 

 them should not be treated as a guide to the classification 

 of other objects generally. But when once we regard 

 these resemblances as hereditary in their origin, we see 

 that the sciences of systematic botany and zoology have 

 a special character of their own. There is no reason to 



