174 NAMES AND PROPOSITIONS. 



not animals ; and it must connote something more 

 than animal connotes, otherwise all animals would be 

 men. This surplus of connotation this which the 

 species connotes over and above the connotation of 

 the genus is the Differentia, or specific difference ; 

 or, to state the same proposition in other words, the 

 Differentia is that which must be added to the conno- 

 tation of the genus, to complete the connotation of 

 the species. 



The word man, for instance, exclusively of what 

 it connotes in common with animal, also connotes 

 rationality, and at least some approximation to that 

 external form, which we all know, but which, as we 

 have no name for it considered in itself, we are 

 content to call the human. The differentia, or specific 

 difference, therefore, of man, as referred to the genus 

 animal, is that outward form and the possession of 

 reason. The Aristotelians said, the possession of 

 reason, without the outward form. But if they 

 adhered to this, they would have been obliged to call 

 the Houyhnhms men. The question never arose, and 

 they were never called upon to decide how such a 

 case would have affected their notion of essentiality. 

 But, so far as it is possible to determine how language 

 would be used in a case which is purely imaginary, 

 we may say that the Houyhnhms would not be called 

 men, and that the term man, therefore, requires other 

 conditions besides rationality. The schoolmen, how- 

 ever, were satisfied with taking such a portion of the 

 differentia as sufficed to distinguish the species from 

 all other existing things, although by so doing they 

 might not exhaust the connotation of the name. 



6. And here, to prevent the notion of differentia 

 from being restricted within too narrow limits, it is 



