100 NAMES AND PROPOSITIONS. 



genera above (Species Praedieabilis and Species Subjicibilis). But every 

 Kind which admits of division into real Kinds (as animal into mammal, 

 bird, fish, etc., 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 predica- 

 bles, 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 distin- 

 guishes 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 signifies. 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 

 Differentia ; 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 at- 

 tributes by which the species man is distinguished from other species of 

 the same genus: would this attribute serve equally well for a differentia? 

 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 supposed 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, and the differences 

 which are not of kind ; they meant to intimate that genera and species 

 must be Kinds. Their notion of the essence of a thing was a vague notion 

 of a something which makes it what it is, ^. e., which makes it the Kind of 

 thing that it is — which causes it to have all that variety of properties which 

 distinguish its Kind. But when the matter came to be looked at more 

 closely, nobody could discover what caused the thing to have all those prop- 

 erties, nor even that there was any thing which caused it to have them. 

 Logicians, however, not liking to admit this, and being unable to detect 

 what made the thing to be what it was, satisfied themselves with what 

 made it to be what it Avas called. Of the innumerable properties, known 

 and unknown, that are common to the class man, a portion only, and of 

 course a very small portion, are connoted by its name ; these few, however, 

 will naturally have been thus distinguished from the rest either for their 

 greater obviousness, or for greater supposed importance. These prop- 

 erties, then, which were connoted by the name, logicians seized upon, and 

 called them the essence of the species; and not stopping there, they af- 

 firmed them, in the case of the infima species, to be the essence of the in- 

 dividual too ; for it was their maxim, that the species contained the " whole 

 essence" of the thing. Metaphysics, that fertile field of delusion propa- 

 gated by language, does not afford a more signal instance of such delusion. 

 On this account it was that rationality, being connoted by the name man, 

 was allowed to be a differentia of the class; but the peculiarity of cook- 

 ing their food, not being connoted, was relegated to the class of accidental 

 properties. 



