298 THE SCIENCE OF LOGIC 



ment on account of its known connexion with some other already 

 known judgment or judgments, it is called a conclusion, and its 

 evidence is mediate. If, on the contrary, we assent to it on its 

 own account, because of the direct appeal it makes to our intellect 

 as true, it is called a principle, or a j^-evident, or immediately 

 evident, truth. 



It needs but little experience of life, however, to convince us 

 that men differ widely in the judgments they accept as self- 

 evident ; and this is, in part at least, because men s assents are 

 influenced not by intellectual evidence alone, but also by non- 

 intellectual motives. Their estimate of the evidence is partly 

 dependent on their character and dispositions, their mental habits 

 and training, their likes and dislikes, their will, passions, emotions, 

 etc. (231). These are psychological influences, of which logic can take 

 no direct notice. But when there is question of assent to judgments 

 on immediate evidence, of estimating this latter, and discriminating 

 between real and apparent evidence, it is not easy to divide 

 the misleading influences at work into psychological and logical. 

 Against influences supposed to belong to the former class passion, 

 prejudice, party-spirit, precipitancy, etc., logic can merely give 

 a general warning (203). Only when the source or cause of the 

 deception is a violation of some logical principle, can logic deal more 

 effectually with it. Of the source of the deception, the victim of 

 a fallacy is, of course, always and necessarily unconscious : the 

 mind aware of its deception would be no longer deceived. But 

 when deliberate reflection on our thought-processes brings into 

 consciousness the causes which have misled us, these will always 

 appear to have been either inadvertent and indeliberate violations 

 of some of the laws and principles of correct thought, propounded 

 in logic, or else to have been misleading influences of a more subtle 

 and subjective kind, springing from character, prejudice, mental 

 training, etc. The former alone we shall call Logical Fallacies. 



We may, therefore, define a Logical Fallacy as a violation of 

 some logical principle, calculated to lead to error by reason of its 

 apparent validity. 



272. SOME ATTEMPTED &quot; CLASSIFICATIONS&quot; OF FALLACIES. 

 &quot; FORMAL &quot; AND &quot; MATERIAL &quot; FALLACIES. (a} The line of 

 thought we have just followed suggests a classification of fallacies 

 made by John Stuart Mill : a &quot; catalogue of the varieties of ap 

 parent evidence which are not real evidence &quot;.* 



1 Logic, V., i., i. 



