DEFINITION. 95 



Definitions of this kind are what logicians have had in view when 

 they laid down the rule, that the definition of a species should be per 

 genus et different iam. Pift'erentia being seldom taken to mean the 

 whole of the peculiarities constitutive of the species, but some one of 

 those peculiarities only, a complete definition would be j)C)- genus et 

 dffercnfias, rather than different'uim. It would include, with the name 

 of the superior genus, not merely some attribute which, distinguishes 

 the species intended to be defined from all other Species of the same 

 genus, but all the attributes implied in the name of the species, which 

 tlie name of the superior genus has not already implied. The asser- 

 tion, however, that a definition must of necessity consist of a genus 

 and difierentice, is not tenable. It was early remarked by logicians, 

 that the sunnnuiii genus in any classification, having no genus superior 

 to itself, could not be defined in this manner. Yet we have seen that 

 all names, except those of our elementary feelings, are susceptible of 

 definition in the strictest sense; by setting fortli in words the constit- 

 uent parts of the fact or phenomenon, of which the connotation of every 

 word is ultimately composed. 



§ 5. Although the first kind of imperfect definition (which defines a 

 cohnotative term by a part only of what it connotes, but a part sufficient 

 to mark out con-ectly the boundaries of its denotation), has been con- 

 sidered by the ancients, and by logicians in general, as a complete 

 definition ; it has always been deemed necessary that the attributes 

 employed should really form part of the connotation; for the rule was 

 that the definition must be drawn from the essence of the class ; and this 

 would not have been the case if it had been in any degree made up of 

 attributes not connoted by the name. The second kind of imperfect 

 definition, therefore, in- which the name of a class is defined by any of 

 its accidents — that is, by attributes which are not included in its conno- 

 tation — has been rejected from the rank of genuine Definition by all 

 philosophers, and has been termed Description. 



This kind of imperfect definition, however, takes its, rise frortl the 

 same cause as the other, namely, the willingness to accept as a defini- 

 tion anything which, whether it expounds the meaning of the name or 

 not, enables us to discriminate the things denoted by the name from all 

 other things, and consequently to employ the term in predication with- 

 out deviating from established usage. This purpose is .duly answered 

 by stating any (no matter what) of the attributes which are common to 

 the whole of the class, and peculiar to it ; or any combination of attri- 

 butes which may happen to be peculiar to it, although separately each 

 of those attributes may be common to it with some other things. It ia 

 only necessary that the definition (or description) thus formed, shcmld 

 be convertible with the name which it professes to define ; that is, should 

 1x3 exactly co-extensive with it, being predicable of everything of ^vhich 

 it is predicable, and of nothing of which it is not predicable : although 

 the attributes specified may have nc^ connexion with those which men 

 had in view Avhen they foi-pied or recognized the class, and gave it a 

 name. The following are coiTect definitions of Man, according to this 

 test : Man is a mammiferous animal, baring (by nature) two hands 

 (for the human species answers to this description, and no other animal 

 does) : Man is an animal who cooks his food ; Man is a featherless 

 biped. 



