CLASSIFICATION AND THE PREDICABLES. 139 



cannot be a genus, because it has no species under it ; but it 

 is itself a species, both with reference to the individuals below 

 and to the genera above (Species Praedicabilis and Species 

 Subjicibilis.) But every Kind which admits of division into 

 real Kinds (as animal into mammal, bird, fish, &c., or bird 

 into various species of birds) is a genus to all below 

 it, a species to all genera in which it is itself included. 

 And here we may close this part of the discussion, and pass 

 to the three remaining predicables, Differentia, Proprium, and 

 Accidens. 



5. To begin with Differentia. This word is correlative 

 with the words genus and species, and as all admit, it signifies 

 the attribute which distinguishes a given species from every 

 other species of the same genus. This is so far clear : but we 

 may still ask, which of the distinguishing attributes it signi- 

 fies. For- we have seen that every Kind (and a species must 

 be a Kind) is distinguished from other Kinds not by any one 

 attribute, but by an indefinite number. Man, for instance, is 

 a species of the genus animal : Rational (or rationality, for it 

 is of no consequence here whether we use the concrete or the 

 abstract form) is generally assigned by logicians as the Diffe- 

 rentia ; and doubtless this attribute serves the purpose of 

 distinction : but it has also been remarked of man, that he 

 is a cooking animal ; the only animal that dresses its food. 

 This, therefore, is another of the attributes by which the 

 species man is distinguished from other species of the same 

 genus : would this attribute serve equally well for a diffe- 

 rentia ? The Aristotelians say No ; having laid it down that 

 the differentia must, like the genus and species, be of the 

 essence of the subject. 



And here we lose even that vestige of a meaning grounded 

 in the nature of the things themselves, which may be sup- 

 posed to be attached to the word essence when it is said that 

 genus and species must be of the essence of the thing. There 

 can be no doubt that when the schoolmen talked of the 

 essences of things as opposed to their accidents, they had 

 confusedly in view the distinction between differences of kind, 



