xh^ PREFACE. 



of any kind. The operations of the human intelle^l: are of three 

 kinds ; firft, we apprehend the fimple idea of any thing ; fecondly, 

 we perceive the truth of axioms or felf-evident propofitions ; and, 

 laftly, from thefe, by the difciirfiis mentis^ other proportions are de- 

 duced, which, in that way, are faid to be proved or demonftrated. 

 And this laft operation of the Mind is what is properly called 

 Science ; and, to Ihew the nature of this operation, and how the 

 Mind may proceed in it without hazard of error, is the bufniefs of 

 Logic ; which, at the fame time that it direds the operation of the 

 Mind in other Sciences, is itfelf a Science, fo great and fo won- 

 derful, that if I could believe Ariftotlc to have been the inven- 

 tor of it, I ihiould confider him as fomething more than mortal 

 man : Nor can I wonder that when Philofophy was firft introduced 

 into the weftern parts of Europe, after the fall of the Roman empire, 

 the Schoolmen^ as they are called, beftowed fo much labour upon it ; 

 a great deal too much, according to the general opinion of this age; 

 but be that as it will, I am fure it is much too little ftudicd at pre- 

 fent ; and I very plainly perceive the want of the knowledge of it 

 in almoft all the works of Reafoning or Philofophy that are now 

 publifiied. It is fo Httle underftood that I muft fay fomething more 

 to convince the generality of readers that it is of any value at all. 



In the firft place, we fliould confider how it is poffible that we 

 can be men of Science if we do not underftand what Science is : 

 Now the purpofe of Ariftotle's Logic is to difcover what Science is, 

 as he has told us himfelf in the beginning of his Analytics. To 

 be convinced how great a work this was, we need only read the 

 "Thea^tctcs of Plato, in which that queflion is agitated, and much is 

 faid upon it''^ ; and I have no doubt but that it was with the view to 

 decide what Plato has left altogether undecided, that Ariftotle com- 



pofed his fyftem of Logic 



It 



* See what I have faid of this dialogue, Vol. II, p. 68, 



