224 



by which mankind are afflicted can be directly traced.* Hence, the 

 rules of definition constitute perhaps the most important part of logical 

 doctrine, and too great care cannot be expended on their application. 



These rules, though generally neglected, are extremely simple in their 

 nature, and to some of them we will briefly refer : 



The use of a definition in logical discourse is merely to ascertain and 

 determine the sense in which the term defined is to be used ; or, in other 

 words, the whole office of a definition is simply to describe the class of 

 objects denoted by the term. In effecting this, the definition must, to 

 some extent, disclose the nature of the tiling denoted by the term, but it 

 does so only to the extent necessary to fix the meaning of the term ; and 

 beyond this, it is not any part of its function to e.xpress the nature of the 

 thing denoted. 



Another obvious rule Is that, while it is necessary for the definition of 

 a term to contain enough to distinguish or define the class of things 

 denoted by it from all other classes of things, it is almost equally import- 

 ant that when this is effected it should contain nothing more. In other 

 words, a correct logical definition, to use the technical expression, must 

 be 2)^1" genus et differentia — that is to say, it must specify the general class 

 to which the species of things denoted by the term belongs, and the 

 essential characteristics by which this is distinguished from other species 

 of the genus, or, in other words, the specific difference ; and the last, i. e., 

 the specific difference, should contain only sufficient characteristics to 

 distinguish the species, and no more. Having stated the essential char- 

 acteiistic necessary to distinguish the species, all others may be demon- 

 strated, or proved by evidence ; and it is therefore illegitimate to assume 

 them. 



Another rule — which will complete the list of those necessary to be 

 referred to here — is that the words used in the definition should be more 

 clear, or more susceptible of definition tlian the term defined. Or, in 

 other words, that we do not fall into the error of trying to explain the 

 unknown by something still more unknown {Ignotum per ignotius). 



(3) The above rules have been habitually violated in the definitions 

 given us by political writers; and the result has been that the fa lacy 

 under consideration, and especially that form of it which consists in the 

 use of question-begging terms, is one of the most fruitful sources of polit- 

 ical heresies. A conspicuous instance of this is furnished by Austin, 

 whose theory, as we have observed, is wholly deduced from his assumed 

 definition of the law ; which in turn derived its plausibility from the 

 ambiguity of that term in our language, in denoting at once lex and jus. 

 But in the current definitions of the State, we will find equally con- 

 spicuous, and perhaps even more dangerous examples of this fallacy. 



*As Hobbes says: "A man that seeketh precise trutli had need to remember what 

 every name he uses stands for, and to phvce it accordingly, or else lie will find himself 

 entangled iu words as a bird in lime twigs ; the more he struggles, the more belimed."— 

 Lev , pp. 24, 25. 



