on ourselves or others. The greatest danger, and which we are perpetually expofed to in reasoning, is, where the two fenfes or fignifications of one term are near akin, and not plainly distinguished, and yet they are really fufficiently different in their fenfe, to lead us into great mistakes, if we are not watchful. And indeed the greatest part of controverfies in the facred or civil life arife from the different fenfes that are put upon words, and the different ideas which are included in them; as have been shewn at large in the FIRST PART OF LOGIC, Chap. IV. which treats of words and terms.

There is, after all these, another fort of sophism, which is wont to be called on imperfect enumeration, or a falfe induction, when from a few experiments or obfervations men infer general theorems and universal propofitions. But this is fufficiently noticed in the foregoing chapter, where we treated of that fort of fyllogifm which is called induction.

SECT. II.

TWO GENERAL TESTS OF TRUE SYLLOGISMS, AND METHODS OF SOLVING ALL SOPHISMS.

BESIDES

ESIDES the special description of true fyllogifms and fophifms already given, and the rules by which the one are framed, and the other refuted, there are these two general methods of reducing all fyllogifms whatfoever to a test of their truth or falfehood.

I. The first is, that the premises muft, at least implicitly, contain the conlufion; or thus, One of the premises must contain the conclufion, and the other muft fhew that the conclufi on is contained in it. The reafon of this rule is this; when any propofition is offered to be proved, it is neceffary to find another propofition which confirms it, which may be called the containing propofition; but because the second muft not contain the firft in an exprefs manner,and in the

fame words, therefore it is neceffary that a'third or of tenfive propofition be found out, to fhew that the fecond propofition contains the firft, which was to be proved. Let us make an experiment of this fyllogifm: Whosoever is a flave to his natural inclination is miferable; The wicked man is a flave to his natural inclinations; therefore The wicked man is miferable. Here it is evident that the major propofition contains the conclufion; for, under the general character of a flave to natural inclinations, a wicked man is contained or included; and the minor propofition de. clares it; whence the conclufion is evidently deduced, that the wicked man is miferable.

In many affirmative fyllogifms we may fuppofe either the major or the minor to contain the conclufion, and the other to fhew it; for there is no great difference. But in negative fyllogifms it is the negative propofition that contains the conclufion, & the affirmative propofition fhews it; asĒvery wife man mafters his passions; No angry man masters his paffions; therefore No angry man is wife. Here it is more na tural to fuppofe the minor to be the contained proposition; it is the minor implicitly denies wisdom concerning an an gry man, because mastering the paffions is included in wifdom, and the major fhews it.

Note.... This rule may be applied to complex and conjunctive, as well as fimple fyllogifms, and is adapted to fhew the truth or falfehood of any of them.

II. The fecond is this; As the terms in every fyllogifm are ufually repeated twice, fo they must be taken precifely in the fame fenfe in both places: For the greatest part of mif takes that arife in forming fyllogifms is derived from fome little difference in the fenfe of one of the terms in the two parts of the fyllogifm wherein it is ufed. Let us confider the following fophifms.

there

1. It is a fin to kill a man; A murderer is a man ; fore It is a fin to kill a murderer. Here the word kill in

* It is confeffed that conditional and disjunctive major propofitions do expressly contain all that is in the conclufion; but then it is not in a certain and conclufive manner, but only in a dubious form of speech, and mingled with other terms; and therefore it is not the fame exprefs proposition.

the first propofition fignifies to kill unjustly, or without law; in the conclufion it is taken abfolutely for putting a man to death in general, and therefore the inference is not good.

2.

What I am, you are not; but I am a man; therefore You are not a man. This is a relative fyllogifm: But if it be reduced to a regular categorical form, it will appear there is ambiguity in the terms, thus; What I am, is a man; You are not what I am; therefore you are not a man. Here what I am in the major propofition is taken Specially for my nature; but in the minor propofition the fame words are taken individually for my perfon; therefore the inference mult be falfe, for the fyllogifm does not take the term what I am both times in the fame sense.

3. He that fays you are an animal, fays true; but He that fays you are a goofe, fays you are an animal; therefore He that fays you are a goofe, fays true. In the major propofition the word animal is the predicate of an incidental propofition; which incidental propofition being affirmative, renders the predicate of it particular, according to chap. II. fect. 2. axiom 3. and confequently the word animal there fignifies only human animality. In the minor propofition the word animal, for the fame reafon, fignifies the animality of a goofe; whereby it becomes an ambiguous term, and unfit to build the conclufion upon. Or if you fay, the word animal in the minor is taken for human animality, then the minor is evidently falfe.

It is from this laft general teft of fyllogifms that we derive the custom of the refpondent in anfwering the arguments of the opponent, which is to distinguish upon the major or minor propofition, and declare which term is ufed in two fenfes, and in what fenfe the propofition may be true, and in what fenfe it is falfe.

CHAP. IV.

SOME GENERAL RULES TO DIRECT OUR REASONING.

MOST

OST of the general and special directions given to form our judgments aright in the preceding part of logic might be rehearfed here; for the judgments which we pass upon things are generally built on fome fecret reasoning or argument by which the propofition is fuppofed to be proved. But there may be yet fome far ther affiftances given to our reasoning powers in their fearch after truth, and an observation of the following rules will be of great importance for that end.

RULE I. "Accuftom yourselves to clear and diftin&t ideas, to evident propofitions, to strong and convincing arguments." Converfe much with thofe friends, and thofe books, and thofe parts of learning, where you meet with the greatest clearness of thought, and force of rea foning. The mathematical fciences, and particularly arithmetic, geometry, and mechanics, abound with these advantages: And if there were nothing valuable in them for the ufes of human life, yet the very fpeculative parts of this fort of learning are well worth our study; for by perpetual examples they teach us to conceive with clearnefs, to connect our ideas and propofitions in a train of dependence, to reason with strength and demonstration, and to diftinguish between truth and falfehood. Something of thefe fciences should be ftudied by every man who pretends to learning, and that, as Mr. Locke expreffes it, not fo much to make us mathematicians, as to make us reasonable creatures.

We should gain fuch a familiarity with evidence of perception and force of reafoning, and get fuch a habit of difcerning clear truths, that the mind may be foon offended with obfcurity and confufion: Then we fhall, as it were, naturally and with ease restrain our minds from rash judgment, before we attain juft evidence of the prop ofition which is offered to us; and we fhall with the

fame eafe, and, as it were naturally, feize and embrace every truth that is propofed with just evidence.

The habit of conceiving clearly, of judging justly, and of reasoning well, is not to be attained merely by the happiness of conftitution, the brightnefs of genius, the best natural parts, or the best collection of logical precepts: it is cuftom and practice that must form and establish this habit. We must apply ourselves to it till we perform all this readily, and without reflecting on rules. A coherent thinker and a strict reasoner is not to be made at once by a fet of rules, any more than a good painter or mufician may be formed extempore, by an excellent lecture on mufic or painting. It is of infinite importance therefore in our younger years to be taught both the value and the practice of conceiving clearly and reasoning right: For, when we are grown up to the middle of life, or paft it, it is no wonder that we fhould not learn good reasoning, any more than that an ignorant clown fhould not be able to learn fine language, dancing, or a courtly behaviour, when his ruftic airs have grown up with him till the age of forty.

For want of this care, fome perfons of rank and education dwell all their days among obfcure ideas; they conceive and judge always in confufion; they take weak arguments for demonftration; they are led away with the difguifes and fhadows of truth. Now, if fuch perfons happen to have a bright imagination, a volubility of fpeech, and a copioufnefs of language, they not only impofe many errors upon their own understandings, but they Atamp the image of their own mistakes upon their neighbours alfo, and spread their errors abroad.

It is a matter of just lamentation and pity, to confider the weakness of the common multitude of mankind in this refpect, how they receive any thing into their affent upon the most trifling grounds. True reafoning hath very little fhare in forming their opinions. They refift the moft convincing arguments by an obftinate adherence to their prejudices, and believe the most improbable things with the greatest affurance. They talk of the abftrufeft myfteries, and determine upon them with the utmost confidence, and without juft evidence either from reafon or