674 THE PRINCIPLES OF SCIENCE. [CHAP. 



thought or in actual proximity of space, those objects be- 

 tween which identity has been detected. Accordingly, the 

 value of classification is co-extensive with the value of 

 science and general reasoning. Whenever we form a class 

 we reduce multiplicity to unity, and detect, as Plato said, 

 the one in the many. The result of such classification is 

 to yield generalised knowledge, as distinguished from the 

 direct and sensuous knowledge of particular facts. Of 

 every class, so far as it is correctly formed, the principle 

 of substitution is true, and whatever we know of one object 

 in a class we know of the other objects, so far as identity 

 has been detected between them. The facilitation and 

 abbreviation of mental labour is at the bottom of all mental 

 progress. The reasoning faculties of Newton were not 

 different in nature from those of a ploughman; the dif- 

 ference lay in the extent to which they were exerted, and 

 the number of facts which could be treated. Every think- 

 ing being generalises more or less, but it is the depth and 

 extent of his generalisations which distinguish the philo- 

 sopher. Now it is the exertion of the classifying and 

 generalising powers which enables the intellect of man to 

 cope in some degree with the infinite number of natural 

 phenomena. In the chapters upon combinations and 

 permutations it was made evident, that from a few element- 

 ary differences immense numbers of combinations can be 

 produced. The process of classification enables us to resolve 

 these combinations, and refer each one to its place according 

 to one or other of the elementary circumstances out of which 

 it was produced. We restore nature to the simple condi- 

 tions out of which its endless variety was developed. As 

 Professor Bowen has said, 1 " The first necessity which is 

 imposed upon us by the constitution of the mind itself, is 

 to break up the infinite wealth of Nature into groups and 

 classes of things, with reference to the"ir resemblances and 

 affinities, and thus to enlarge the grasp of our mental 

 faculties, even at the expense of sacrificing the minuteness 

 of information which can be acquired only by studying 

 objects in detail. The first efforts in the pursuit of know- 

 ledge, then, must be directed to the business of classification. 



1 A Treatise on Logic, or, the Laws of Pure Thought, by Francis 

 Bowen, Professor of Moral Philosophy in Harvard College, Cam- 

 bridge, United States, 1866, p. 315. 



