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a predicate; as in thefe, It rains, It fnows. 2. In fome propofitions either term may be made the fubject or the predicate as
like beft; as in this, Virtue is the road to happiness. 3. The fame example may ferve to fhew, that it is fometimes difficult to fay, whether a propofition be universal or particular. 4. The quality of fome propofitions is fo dubious, that logicians have never been able to agree whether they be affirmative or negative; as in this propofition, Whatever is infentient is not an animal. 5. As there is one clafs of propofitions which have only two terms, to wit, one fubject and one predicate, which are called categorical propofitions; fo there are many claffes that have more than two terms. What Ariftotle delivers in this book is applicable only to categorical propofitions; and to them only the rules concerning the converfion of propofitions, and concerning the figures and modes of fyllogifins, are accommodated. The fubfequent writers of logic have taken notice of fome of the many claffes of complex propofitions, and have given rules adapted to them; but finding this work endless, they have left us to manage the rest by the rules of common fenfe.
Account of the First Analytics.
SECT. I. Of the Converfion of Propofitions.
N attempting to give fome account of
the Analytics and of the Topics of A-. riftotle, ingenuity requires me to confefs, that tho' I have often purpofed to read the whole with care, and to understand what is intelligible, yet my courage and patience. always failed before I had done. Why fhould I throw away fo much time and painful attention upon a thing of fo little real ufe? If I had lived in thofe ages when the knowledge of Ariftotle's Organon intitled a man to the higheft rank in philofophy, ambition might have induced me to employ upon it fome years of painful study; and lefs, I conceive, would not be fufficient. Such reflections as thefe, always got the better of my refolution, when
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when the first ardor began to cool. All I
fay is, that I have read fome parts of the different books with care, fome flightly, and fome perhaps not at all. I have glanced over the whole often, and when any thing attracted my attention, have dipped into it till my appetite was fatisfied. Of all reading it is the most dry and the most painful, employing an infinite labour of demonftration, about things of the most abftract nature, delivered in a laconic style, and often, I think, with affected obfcurity; and all to prove general propofitions, which when applied to particular inftances appear felf-evident.
There is probably but little in the Categories or in the book of Interpretation, that Ariftotle could claim as his own invention but the whole theory of fyllogifms he claims as his own, and as the fruit of much time and labour. And indeed it is a stately fabric, a monument of a great genius, which we could wish to have been more usefully employed. There must be fomething however adapted to please the human understanding, or to flatter human pride, in a work which occupied men of fpeculation for more than a thousand
years. Thefe books are called Analytics, because the intention of them is to refolve all reafoning into its fimple ingredients.
The first book of the First Analytics, confifting of forty-fix chapters, may be divided into four parts; the first treating of the converfion of propofitions; the fecond, of the ftructure of fyllogifms in all the different figures and modes; the third, of the invention of a middle term; and the laft, of the refolution of fyllogifms. We fhall give a brief account of each.
To convert a propofition, is to infer from it another propofition, whose fubject is the predicate of the firft, and whofe predicate is the subject of the first. This is reduced by Ariftotle to three rules. 1. An univerfal negative may be converted into an univerfal negative: thus, No man is a quadruped; therefore, No quadruped is a man. 2. An univerfal affirmative can be converted only into a particular affirmative: thus, All men are mortal; therefore, Some mortal beings are men. 3. A particular affirmative may be converted into a particular affirmative: as, Some men are juft; therefore, Some just perfons are men. When a propofition may be con
verted without changing its quantity, this is called fimple converfion; but when the quantity is diminished, as in the univer fal affirmative, it is called converfion per accidens.
There is another kind of converfion, omitted in this place by Ariftotle, but fupplied by his followers, called converfion by contrapofition, in which the term that is contradictory to the predicate is put for the fubject, and the quality of the propofition is changed; as, All animals are fentient; therefore, What is infentient is not an animal. A fourth rule of converfion therefore is, That an univerfal affirmative, and a particular negative, may be converted by contrapofition.
SECT. 2. Of the Figures and Modes of pure Syllogifms.
A fyllogifm is an argument, or reasoning, confifting of three propofitions, the laft of which, called the conclufion, is inferred from the two preceding, which are called the premises. The conclufion having two terms, a fubject and a predicate, its predicate