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CH APT EU I. 

 OF FALLACIES IN GENERAL. 



1. IT is a maxim of the schoolmen, that " con- 

 trariorum eadem est sciential" we never really know 

 what a thing is, unless we are also ahle to give a 

 sufficient account of its opposite. Conformably to 

 this maxim, one considerable section, in most treatises 

 on Logic, is devoted to the subject of Fallacies ; and 

 the practice is too well worthy of observance, to allow 

 of our departing from it. The philosophy of reason- 

 ing, to be complete, ought to comprise the theory of 

 bad as well as of good reasoning. 



We have endeavoured to ascertain the principles 

 by which the sufficiency of any proof can be tested., 

 and by which the nature and amount of evidence 

 needful to prove any given conclusion can be deter- 

 mined beforehand. If these principles were adhered 

 to, then although the number and value of the truths 

 ascertained would be limited by the opportunities, or by 

 the industry, ingenuity, and patience, of the individual 

 inquirer, at least error would not be embraced instead 

 of truth. But the general consent of mankind, 

 founded upon all their experience, vouches for their 

 being far indeed from even this negative kind of per- 

 fection in the employment of their reasoning powers. 



In the conduct of life in the ordinary business of 

 mankind wrong inferences, incorrect interpretations 

 of experience, unless after much culture of the think- 

 ing faculty, are absolutely inevitable: and with most 

 people after the highest degree of culture they ever 

 attain (unless where the events of their daily life 



