194 NAMES AND PROPOSITIONS. 



deemed the natural, classification of things, namely, 

 the division of them into Kinds ; and to show the place 

 which each Kind occupies, as superior, collateral, or 

 subordinate, among other Kinds. This notion would 

 account for the rule that all definition must necessarily 

 be per genus et differentiam, and would also explain 

 why any one differentia was deemed sufficient. But 

 to expound, or express in words, a distinction of Kind, 

 has already been shown to be an impossibility: the 

 very meaning of a Kind is, that the properties which 

 distinguish it do not grow out of one another,, and 

 cannot therefore be set forth in words, even by impli- 

 cation, otherwise than by enumerating them all : and 

 all are not known, nor ever will be so. It is idle, 

 therefore, to look to this as one of the purposes of a 

 definition : while, if it be only required that the defi- 

 nition of a Kind should indicate what Kinds include 

 it or are included by it, any definitions which expound 

 the connotation of the names will do this : for the name 

 of each class must necessarily connote enough of its 

 properties to fix the boundaries of the class. If the 

 definition, therefore, be a full statement of the connota- 

 tion, it is all that a definition can be required to be. 



6. Of the two incomplete or unscientific modes 

 of definition, and in what they differ from the com- 

 plete or scientific mode, enough has now been said. 

 We shall next examine an ancient doctrine, once 

 generally prevalent and still by no means exploded, 

 which I regard as the source of a great part of the 

 obscurity hanging over some of the most important 

 processes of the understanding in the pursuit of 

 truth. According to this, the definitions of which we 

 have now treated are only one of two sorts into which 

 definitions may be divided, viz., definitions of names, 



