CLASSIFICATION OF FALLACIES. 303 



creates a presumption in favour of a proposition; not suffi 

 cient for belief, but sufficient to cause the strict principles of 

 a regular induction to be dispensed with, and creating a pre 

 disposition to believe it on evidence which would be seen to be 

 insufficient if no such presumption existed. This class, com 

 prehending the whole of what may be termed Natural 

 Prejudices, and which I shall call indiscriminately Fallacies of 

 Simple Inspection or Fallacies a priori, shall be placed at the 

 head of our list. 



Fallacies of Inference, or erroneous conclusions from 

 supposed evidence, must be subdivided according to the nature 

 of the apparent evidence from which the conclusions are 

 drawn ; or (what is the same thing) according to the parti 

 cular kind of sound argument which the fallacy in question 

 simulates. But there is a distinction to be first drawn, which 

 does not answer to any of the divisions of sound arguments, 

 but arises out of the nature of bad ones. We may know 

 exactly what our evidence is, and yet draw a false conclusion 

 from it; we may conceive precisely what our premises are, 

 what alleged matters of fact, or general principles, are the 

 foundation of our inference ; and yet, because the premises 

 are false, or because we have inferred from them what they 

 will not support, our conclusion may be erroneous. But a 

 case, perhaps even more frequent, is that in which the error 

 arises from not conceiving our premises with due clearness, 

 that is, (as shown in the preceding Book,*) with due fixity : 

 forming one conception of our evidence when we collect or 

 receive it, and another when we make use of it; or unadvisedly, 

 and in general unconsciously, substituting, as we proceed, dif 

 ferent premises in the place of those with which we set out, or 

 a different conclusion for that which we undertook to prove. 

 This gives existence to a class of fallacies which may be justly 

 termed (in a phrase borrowed from Bentham) Fallacies of 

 Confusion ; comprehending, among others, all those which have 

 their source in language, whether arising from the vagueness or 

 ambiguity of our terms, or from casual associations with them. 



* Supra, p. 204. 



