CLASSIFICATION OF FALLACIES. 345 



unmistakeably under some one of these classes, as to 

 be incapable of being referred to any other. Erro- 

 neous arguments do not admit of such a sharply-cut 

 division as valid arguments do. An argument fully 

 stated, with all its steps distinctly set out, in language 

 not susceptible of misunderstanding, must, if it be 

 erroneous, be so in some one, and one only, of these 

 five modes ; or indeed of the first four, since the fifth, 

 on such a supposition, would vanish. But it is not in 

 the nature of bad reasoning to express itself thus 

 unambiguously. When a sophist, whether he is im- 

 posing upon himself or attempting to impose upon 

 others, can be constrained to throw his sophistry into 

 so distinct a form, it needs, in a large proportion of 

 cases, no further exposure. 



In all arguments, everywhere but in the schools, 

 some of the links are suppressed; a fortiori when the 

 arguer either intends to deceive, or is a lame and 

 inexpert thinker, little accustomed to bring his rea- 

 soning processes to any test: and it is in those steps 

 of the reasoning which are made in this tacit and half- 

 conscious, or even wholly unconscious manner, that 

 the error oftenest lurks. In order to detect the 

 fallacy, the proposition thus silently assumed must 

 be supplied; but the reasoner, most likely,, has never 

 really asked himself what he was assuming: his con- 

 futer, if unable to extort it from him by the Socratic 

 mode of interrogation, must himself judge what the 

 suppressed premiss ought to be in order to support the 

 conclusion. And hence, in the words of Archbishop 

 Whately, " it must be often a matter of doubt, or 

 rather, of arbitrary choice, not only to which genus 

 each kind of fallacy should be referred, but even to 

 which kind to refer any one individual fallacy; for 

 since, in any course of argument, one premiss is 



