CHAPTER III. 

 ERROR AND FALLACIES. 



270. LOGICAL TREATMENT OF ERROR AND ITS SOURCES. 

 Certitude, probability or opinion, doubt, and error such are the 

 various states of mind we experience in our search for truth. 

 It is the function of logic, as a practical science, to guard us 

 against the last of these states, and to enable us, as far as may be, 

 to reach the first. Hence, it analyses our processes of judging, 

 reasoning, generalizing, and demonstrating, with a view to dis 

 cover, and to familiarize us with, the laws and conditions of correct 

 or accurate thought. And we shall be made all the more capable 

 of conforming our own thinking processes to those laws, if we 

 conclude the treatment of our subject by a special study of the 

 more common sources of error, the ways in which we are most 

 likely to fail in the application of logical principles. We shall 

 have a better grasp of the ways in which we ought to think, when 

 we have contrasted these with the ways in which we ought not to 

 think. Not, indeed, that the knowledge of these latter will be an 

 infallible safeguard against error. Nevertheless, it will certainly 

 be helpful to us, &quot; Forewarned, forearmed &quot;. If, for instance, 

 the conclusion of an invalid argument happens to be true, and to 

 be known by us as true, this very knowledge might throw us off 

 our guard and lead us to accepting the argument as valid : it 

 would be less likely to do so were we familiar with the various 

 ways in which deception may creep into an argument. Or, again, 

 if we know the conclusion to be false we know that there must 

 be something wrong with the argument ; but, without a know 

 ledge of the rules of reasoning, and their possible violations, we 

 may be unable to discover what it is precisely that is wrong, es 

 pecially if the premisses seem true : we may know there is a flaw 

 somewhere, without being able to see through it, to explain it, to 

 lay bare the source of it. No doubt, in the course of our work, 

 we have already pointed out, by way of contrast, in illustration 



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