is one number; two and three are five: therefore two and three are one number.

This fort of fophifms is committed when the word All is taken in a collective and a diftributive sense, with- ' out a due diftinction; as, if any one fhould reason thus; all the mufical inftruments of the Jewish temple made a noble concert; the harp is a musical inftrument of the Jewish temple, therefore the harp made a noble concert. Here the word All in the major is collective, whereas fuch a conclufion requires that the word All fhould be diftributive.

It is the fame fallacy when the universal word All or No refers to fpecies in one propofition, and to individuals in another; as, all animals were in Noah's ark ;. therefore no animals perifhed in the flood: whereas in the premise all animals fignifies every kind of animals, which does not exclude or deny the drowning of a thousand individuals..

VIII. The laft fort of fophifms arifes from our abuse of the ambiguity of words, which is the largest and most Extenfive kind of fallacy; and indeed several of the former fallacies might be reduced to this head.

When the words or phrafes are plainly equivocal, they are called Sophifms of Equivocation; as, if we fhould argue thus, he that fends forth a book into the light, defires it to be read; he that throws a book into the fire, fends it into the light :. therefore he that throws a book into the fire defires it to be read.

This fophifm, as well as the foregoing, and all of the like nature, are felved by fhewing the different fenfes of the words, terms or phrafes. Here light in the major propofition fignifies the public view of the world; in. the minor it fignifies the brightness of flame and fire, and therefore the fyllogifm has four terms, or rather it has no middle term, and proves nothing.

But where fuch grofs equivocations and ambiguities. appear in argument. there is little danger of impofing upon ourselves or others. The greatest danger, and which we are perpetually exposed to in reasoning, is, where the two fenfes or fignifications of one term are near a-kin, 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. Ang 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 hath been fhewn at large in the first part of Logic, Chap. IV. which treats of words and terms.

There is, after all thefe, another fort of fophifm which is wont to be called an imperfect Enumeration, or a falfe Induction, when from a few experiments or obfervations, men infer general theorems and univerfal propofitions. But this is fufficiently noticed in the toregoing chapter, where we treated of that fort of fyllogifm which is called Induction.

SECT. II.

Two general Tefts of true Syllogifms, and Methods of folving all Syllogifms.

B

ESIDES the special defcription of true fyllogifms and fophifms already given, and the rules by which the one are framed, and the other refuted, there are thefe 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 conclufion; or thus, one of the premifes must contain the conclufion, and the other muft fhew, that the conclufion is contained in it. The reafon of this rule is this; when any propofition is of-fered to be proved, it is neceflary to find another propofition which confirms it, which may be called the containing Propofitions; but because the fecond must not contain the first in an exprefs manner, and in the same word*, therefore it is neceffary that a third or oftensive

*It is confeffed, that the conditional and disjunctive major propofitions do exprefly contain all that is in the conclufion; but then it is not in a certain and conclusive manner, but only in a dubious form of

II

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. Whofoever

is a flave to his natural inclinations 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 declares it; whence the conclusion is evidently deduced, that the wicked man is miserable.

In many affirmative fyllogifmns 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, and the affirmative propofition fhews it; as, every wife man masters his paffions; no angry man masters his paffion: therefore no angry man is wife. Here it is more natural to suppose the minor to be the containing propofition; it is the minor implicitly denies wifdom concerning an angry man, because mastering the paífions is included in wifdom, and the major fhews it.

Note, this rule may be applied to complex and conjunctive, as well as fimple fyllogiíms, 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, so they must be taken precifely in the fame fenfe in both places: for the greateft part of mistakes, that rife in forming fyllogifms, is derived from fome little difference in the fenfe of one of the terms in the two parts of the fyllogifms wherein it is used. Let us confider the following fophifm.

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

fpeech, and mingled with other terms, and therefore it is not the fame exprefs proposition.

2. What I am you are not; but I am a man; there fore 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 Here what I am in the major propofition, is taken efpecially for my nature; but in the minor propofition the fame words are taken individually for my perfon; therefore the inference must be falle, for the fyllogifms does not take the term what I am both times in the fame fenfe.

are not a man.

3. He that fays you are an animal, fays true; but he that fays you are a goofe, you are an animal; there fore he that fays you are a goofe, fays true. In the major propofition the word animal is the predicate of an incidental proposition; which incidental proposition being affirmative, renders the predicate of it particular, according the Chap. II. Sect. 2. Axiom 3. and confequently the word animal there signifies only human animality. In the minor proposition, the word animal, for the fame reafon, signifies the animality of a goofe; whereby it becomes an ambiguous term, and unfit to build the conclusion 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 diftinguifh upon the major or minor proposition, and declare which term is used in two fenfes, and in what fenfe the proposition may be true, and in what fenfe it is falfe.

CHAP. IV.

Some general Rules to direct our Reafening.

MOST

OST of the general and fpecial directions given. to form our judgments aright in the preceding part of Logic might be rehearfed here; for the judgments

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ich we pafs upon things are generally built on fome cret reafoning or argument by which the proposition fuppofed to be proved. But there may be yet fome rther affittances given to our reafoning powers in heir fearch after truth, and an obfervation of the folwing rules will be of great importance for that end. 1. Kule. Accuftom yourselves to clear and diftinct ideas, evident propofitions, to ftrong and convincing arguments. Converfe much with those friends, and those books and nofe parts of learning where you meet with the greatest learnefs of thought and force of reafoning. The mahematical fciences, and particularly arithmetic, geomery, and mechanics, abound with thefe advantages: and f there were nothing valuable in them for the uses of human life; yet the very speculative parts of this fort of learning are well worth our study; for by perpetual examples they teach us to conceive with clearness, to connect our ideas and propofitions in train of dependence, to reafon with ftrength and demonftration, and to diftinguish between truth and falfehood. Something of thefe fciences fhould 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 fhould gain fuch a familiarity with evidence of perception and force of reafoning, and get fuch a habit of difcerning clear truth, that the mind may be foon offended with obfcurity and confufion: then we fhall (as it were) naturally and with eafe reftrain our minds from rafh judgment, before we attain juft evidence of the propofition which is offered to us; and we shall with the fame ease, and (as it were) naturally feize and embrace every truth that is propofed with juft evidence.

This habit of conceiving clearly, of judging juftly, and of reafoning well, is not to be attained merely by the happiness of conftitution, the brightness of genius, the best natural parts, or the beft collection of logical precepts. It is cuftom and practice that muft 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 ftrict reafoner is not to be made at once by a fet of rules, any