BASIS OF CLASSIFICATION. 189 



in a particular way ; or as one that is dangerous ; and acts 

 accordingly. He has classed together all the creatures 

 that are alike in this particular. And manifestly in choos 

 ing the wood out of which to form his bow, the plant with 

 which to poison his arrows, the bone from which to make 

 his fish-hooks, he identifies them through their chief sensi 

 ble properties as belonging to the general classes, wood, 

 plant, and bone, but distinguishes them as belonging to 

 sub-classes by virtue of certain properties in which they are 

 unlike the rest of the general classes they belong to ; and so 

 forms genera and species. 



And here it becomes manifest that not only is classifica 

 tion carried on by grouping together in the mind things 

 that are like ; but that classes and sub-classes are formed 

 and arranged according to the degrees ofunlikeness. Things 

 widely contrasted are alone distinguished in the lower 

 stages of mental evolution ; as may be any day observed in 

 an infant. And gradually as the powers of discrimination 

 increase, the widely contrasted classes at first distinguished, 

 come to be each divided into sub-classes, differing from 

 each other less than the classes differ ; and these sub-classes 

 are again divided after the same manner. By the continu 

 ance of which process, things are gradually arranged into 

 groups, the members of which are less and less unlike ; 

 ending, finally, in groups whose members differ only as 

 individuals, and not specifically. And thus there tends 

 ultimately to arise the notion of complete likeness. For 

 manifestly, it is impossible that groups should continue to 

 be sub-divided in virtue of smaller and smaller differences, 

 without there being a simultaneous approximation to the 

 notion of no difference. 



Let us next notice that the recognition of likeness and 

 unlikeness, which underlies classification, and out of which 

 continued classification evolves the idea of complete like 

 ness let us next notice that it also underlies the process 



