PREFACE. xlix 



of any thing, nor, by confequence. Science or Demonflration of 

 any kind. 



The next ftep in the procefs of Reafoning is to Propofitions, the 

 nature of which it was neceflary to explain, otherways there could 

 have been no Science of Reafoning. This, accordingly, Ariftotle 

 has done with wonderful accuracy and fubtilty in his book of Inter^ 

 pretation ; the moft abftrufe, 1 think, of all Ariftotle's philofophical 

 writings, and which itfelf needs an interpreter more than any of his 

 books ; and accordingly it has met with an excellent one in a phi- 

 lofopher of the Alexandrian School, Ammonius Hermeias. It was 

 neceffary for the purpofe of Science that Propofitions fhould be re- 

 duced to certain clafles, as well as the terms of which they confift. 

 This has been done by Ariftotle and his interpreter, and all the 

 feveral fpeciefes of them, according to the differences of the 

 predicate, the fubjed:, the matter and manner of the Propofition, 

 have been enumerated, and the number of them muft appear in- 

 credible to thofe who have never thought upon the fubjed, being no 

 lefs than three thoufand and twenty-four * ; and however unnecef- 

 fary it may appear to diftinguifh fo accurately and minutely the fe- 

 veral kinds of Propofitions, thofe who are learned in the Art know 

 very well what confufion it would introduce into Reafoning, if we 

 were to miftake an affirmative for a iiegativc Propofition, a parti- 

 cular for an tmiverfal, a necejary for a cofitingcnt, and fo forth. 



The laft operation, as I have fald, of the difcurfive faculty of the 

 Mind is Syllogifm, to which all our Reafoning, however various 

 and complicated, is reducible. Now every Syllogifm, when it is 

 analyfed, is found tp confift of three terms, and no more, and of 

 two Propofitions, from which the conclufion is inferred, and no 



Vol. III. h more.— 



* See Ammonius upon the Book of Interpretation, Folio 73. 128. and 176. 



