DEFINITION. 159 



Review for January 1828, and containing some opinions which 

 I no longer entertain, I find the following observations on the 

 question now before us ; observations with which my present 

 view of that question is still sufficiently in accordance. 



"The distinction between nominal and real definitions, 

 between definitions of words and what are called definitions 

 of things, though conformable to the ideas of most of the 

 Aristotelian logicians, cannot, as it appears to us, be main- 

 tained. We apprehend that no definition is ever intended to 

 ' explain and unfold the nature of a thing/ It is some confir- 

 mation of our opinion, that none of those writers who have 

 thought that there were definitions of things, have ever suc- 

 ceeded in discovering any criterion by which the definition of 

 a thing can be distinguished from any other proposition 

 relating to the thing. The definition, they say, unfolds the 

 nature of the thing : but no definition can unfold its whole 

 nature ; and every proposition in which any quality whatever 

 is predicated of the thing, unfolds some part of its nature. 

 The true state of the case we take to be this. All definitions 

 are of names, and of names only ; but, in some definitions, it 

 is clearly apparent, that nothing is intended except to explain 

 the meaning of the word ; while in others, besides explaining 

 the meaning of the word, it is intended to be implied that 

 there exists a thing, corresponding to the word. Whether 

 this be or be not implied in any given case, cannot be collected 

 from the mere form of the expression. 'A centaur is an 

 animal with the upper parts of a man and the lower parts of a 

 horse,' and ' A triangle is a rectilineal figure with three sides,' 

 are, in form, expressions precisely similar; although in the 

 former it is not implied that any thing, conformable to the 

 term, really exists, while in the latter it is ; as may be seen by 

 substituting, in both definitions, the word means for is. In 

 the first expression, ' A centaur means an animal,' &c., the 

 sense would remain unchanged: in the second, 'A triangle 

 means,' &c., the meaning would be altered, since it would be 

 obviously impossible to deduce any of the truths of geometry 

 from a proposition expressive only of the manner in which we 

 intend to employ a particular sign. 



