DEFINITION. 



93 



by its consequences indeed rather 

 than by itself. Yet the doctrine in 

 its own proper form now and then 

 breaks out, and has appeared (among 

 other places) where it was scarcely 

 to be expected, in a justly admired 

 work, Archbishop Whately's Loijic* 

 In a review of that work published 

 by me in the Westminster Review for 

 January 1 828, and containing some 

 opinions which I no longer entertain, 

 I find the following observations on 

 the question now before us ; observa- 

 tions with which my present view of 

 that question is still sufficiently in 

 accordance : — 



* In the fuller discussion wliich Arch- 

 bisliop Whately has given to this subject 

 in his later editions, he almost ceases to 

 regard the definitions of names and those 

 of hings as, in any important sense, dis- 

 tinct. He seems (9th ei. p. 145) to limit 

 the no*^ion of a Real Definition to one which 

 " explains anything more of the nature of 

 tiie thing rhiin '^ implied in the name;" 

 (including under the word "implied," not 

 only what the name connotes, but every- 

 thing which can be deduced by reasoning 

 from the attributes connoted). Even this, 

 as he adds, is usually called, not a Defini- 

 tion, but a Description ; and (as it seems 

 to me) rightly so called. A Description, I 

 conceive, can only be ranked among De- 

 finitions when taken (as in the case of the 

 zoological definition of man) to fulfil the 

 true ofl&ce of a Definition, by declaring the 

 connotation given to a word in some special 

 use, as a term of science or art : which 

 special connotation of course would not l>e 

 expressed by the proper definition of the 

 word in its ordinary employment. 



Mr. De Morgan, exactly reversing the 

 doctrine of Archljishop Whately, under- 

 stands by a Real Definition one which 

 contains less^ than the Nominal Definition, 

 provided only that what it contains i.s suf- 

 ficient for distinction, " By real definition 

 I mean such an explanation of the word, 

 be it the whole of the meaning or only part, 

 as will be sufficient to sepai-ate the things 

 contained under that word from all others. 

 Thus the following, I believe, is a complete 

 definition of an elephant : An animal which 

 naturally drinks by drawing the water into 

 its nose, and then spurting it into its 

 mouth." — Formal Logic, p. 36. Mr. De 

 Morgan's general proposition and his ex- 

 ample are at variance ; for the peculiar 

 mode of drinking of the elephant certainly 

 forms no part of the meaning of the word 

 elephant. It could not be said, because a 

 person happened to be ignorant of this 

 property, that he did not know what an 

 elephant means. 



" The distinction between nominal 

 and real definitions, between defini- 

 tions of words and what are called 

 definitions of things, though conform- 

 able to the ideas of most of the Aris- 

 totelian logicians, cannot, as it appears 

 to us, be maintained. We apprehend 

 that no definition is ever intended to 

 ' explain and unfold the nature of a 

 thing.' It is some confirmation 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 pro- 

 position 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 what- 

 ever is predicated of the thing un- 

 folds 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 im- 

 plied that there exists a thing corre- 

 sponding 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 rectili- 

 neal figure with three sides,' are, in 

 form, expressions precisely similar ; 

 although in the former it is not im- 

 plied that any thing, conformable to 

 the term, really exists, while in the 

 latter it is ; as may be seen by sub- 

 stituting, 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 geome- 

 try from a proposition expressive only 



