LESSONS IN LOGIC. 



13 



tioiiH of the rules which Logic lays down as those to which all 

 thinker* aro bound to conform, we may call them logical 



'I'll- most plain and obvious logical fallacies are, of coarse, 

 \hirh iiri-m in. m th" violation of some one of the syllo- 

 : ules already given ; aud upon them it in unnecessary to 

 dwell here at greater length. It may, however, be remarked, 

 rent! nnsouml luxunKints, not uncommonly to be met 

 with, may bo referred to this head. Thus, if a person argued 

 that a certain proposition is false because it has been success- 

 fully demonstrated that the grounds or promises upon which it 

 was supposed by his opponent to rest are false, such a person 

 would bo using an unsound argument, in which he would bo 

 guilty of an illicit process of the major term (which we have 

 already explained) e.g., if the ground adduced to prove the 

 existence of a God, was that it is universally believed, and an 

 instance where no such belief prevailed was cited, then, if an 

 attempt was made to argue that this disproved the existence of 

 a God (instead of merely overthrowing tho single proof which 

 had boon advanced), tho fallacy might be represented thus : 

 " Whatever is universally believed is true ; the existence of a 

 God is not universally believed; therefore it ia not true." So also 

 the fallacy of inferring tho truth of tho promises from the truth 

 of tho conclusion may be stated as follows : " What is univer- 

 sally believed is true ; tho existence of a God is true ; therefore 

 it is universally believed." This ia obviously an instance of 

 undistributed middle. 



Tho middle, however, is often ambiguous, not from being un- 

 distributed, but from being used in a different sense in each 

 premiss. This gives rise to a very largo class of fallacies, to 

 which no one name can be assigned which will comprehend all. 



When the middle term is thus ambiguous in sense, as having 

 in itself, from its own equivocal nature, two significations, we 

 have what is called the Fallacia equivocationis of logicians : 

 e.g., " Light is contrary to darkness ; feathers are light ; there- 

 fore feathers aro contrary to darkness " in which example 

 there are, strictly speaking, four terms. No one would be 

 deceived in such a case as this one ; but it must be remembered 

 that the ambiguity will often be less patent and more likely to 

 escape observation from the promises being placed at a con- 

 siderable distance from each other in the course of a long 

 argument. 



In tho fallacy which is mentioned by logicians under the title 

 of Fallacia amphibolice, the ambiguity arises from an amphi- 

 bolous sentence, i.e., one which is capable of two meanings, not 

 from tho double sense of any of the words, but from its admit- 

 ting of a double construction. " Pyrrhus the Romans shall, I 

 say, subdue " (where the nominative to " subdue " may be 

 either "Pyrrhus" or "tho Romans,") is an instance of such a 

 sentence ; but the English language does not furnish so many 

 of them as the Latin and others like it, and the fallacy is 

 therefore not often to bo met with in this shape. Ordinary 

 language, however, is very elliptical, and thus terms not seldom 

 become practically ambiguous, being differently applied on dif- 

 ferent occasions, although there is no real difference in the 

 sense of tho terms themselves : e.g., " faith," which has in 

 itself but one meaning, ia employed by tho votary of each 

 different religion to denote his own peculiar form of belief. 

 This may load us without caution into arguments somewhat 

 resembling tho fallacy just mentioned. 



An ambiguity arising from tho context also gives rise to the 

 fallacies of Division and Composition. In the fallacy of com- 

 position the middle term is used in tho major premiss in a 

 diati-ibutive, and in the minor in a collective sense : e.g., " Two 

 and throe are odd and even ; five is two and three ; therefore 

 five is odd and even," where it is plain that the middle term 

 "two and three" is ambiguous, denoting, as it doos, in the 

 major premiss the two numbers taken separately, and in tho 

 minor, taken together. This fallacy is employed whenever, as is 

 not unfrequently the case, a person, after establishing some 

 truth separately concerning each member of a class, then infers 

 the same to be true of the whole collectively. This is tho same 

 thing as contending that, because it is not improbable one may 

 throw a six in any one out of a hundred throws, it is not im- 

 probable that one may throw a six in each of them, i.e., a hun- 

 dred times running ; the absurdity of which is plain : but yet, 

 hardly any fallacy is more common or more likely to deceive 

 than this. The fallacy of division, on the other hand, occurs 



where the middle term is first Uken collectively in the major 

 premiss, and then dutributiraly in the minor e^., " two and 

 three are fire ; two and three are two numbers ; therefor* fire 

 is two numbers." Here the middle term u in the major pre- 

 miss, "two and three" together, and in the minor "two and 

 three" taken teparately. The ambiguity of the word "all," 

 which means sometimes " every one separately," and sometime* 

 "all together," not unfrequently gives rise to this fallacy of 

 division. 



There is also another kind of ambiguity occasioned by tho 

 context viz., where the middle term is used in the major pre- 

 miss to signify something considered simply in itself and ae to 

 its essence ; and in the minor for the same thing, with some of 

 its accidents taken into account along with it. The example 

 commonly given of this, the Fallacia Accidental, as it is called, 

 is this : " What ia bought in the market ia eaten ; raw meat 

 is bought in the market; therefore raw meat is eaten." Now 

 in this case the context shows that the middle in the major 

 merely denotes the substance or essence of the thing bought, 

 but that in the minor it ia used for the same thing, with the 

 accident of " being dressed ' ' superadded. If the accident is 

 understood with the middle in the major premiss instead of in 

 the minor, logicians give the fallacy the somewhat lengthy 

 Latin name of Fallacia a dicto secundum quid ad dictum rim- 

 pliciter, i.e., the fallacy of arguing from what ia said with a 

 certain accidental reference to the same thing said absolutely. 



Under the head of ambiguous middle we may also class the 

 Fallacia Figures Dictionis. " This," to quote from Archbishop 

 Whatoly, " ia built on the grammatical structure of language, 

 from men's usually taking for granted that words belonging 

 to each other, as the substantive, adjective, verb, etc., of the 

 same root, have a precisely correspondent meaning, which is 

 by no means universally the case. Such a fallacy could not 

 indeed be even exhibited in strict logical form, which wonld 

 preclude even the attempt at it, since it has two middle terms 

 in sound as well as in sense e.g., " Projectors are unfit to be 

 trusted ; this man has formed a project ; therefore he is unfit tc 

 be trusted : " here there is an assumption that he who forms a 

 project must be a projector ; whereas the bad sense that com- 

 monly attaches to the latter word ia not at all implied in the 

 former." There is a similar want of complete correspondence 

 in the meaning of "presume" and "presuming," "art" and 

 " artful," " design " and " designing," and many other words. 



The lost of the logical fallacies we shall notice separately is 

 the Fallacia Plurium Interrogationum, or, " fallacy of several 

 questions." This consists in asking two or more questions, really 

 distinct, which appear to be but one, so as to entrap an oppo- 

 nent into giving but one answer, which, though only applicable 

 to one of the questions, may be taken as an answer to the other 

 or others. The way in which it must be defeated ia by giving a 

 separate answer to each question. A good instance ia given by 

 Archbishop Whately of its employment by a Parliamentary 

 Committee in 1832, before which a witness was asked " how 

 long the practice had ceased in Ireland of dividing the tithea 

 into four portions;" two questions being thus combined: 1. 

 Had this practice ever existed ? 2. If BO, how long had it been 

 discontinued? Sometimes the ambiguity which gives rise to 

 this fallacy lies not in the meaning but in the distribution of 

 a term : e.g., " Did this man act from such and such a motive r ' ' 

 which may mean, was it one of his motives ? or, was it his sole 

 motive. So also the question, " Has a state a right to enforce 

 laws?" is ambiguous from the fact that "laws" may mean 

 either " some laws," or " any laws, without exception," i.e., may 

 be understood as undistributed or not. 



We now come to the consideration of material or non-logical 

 fallacies, as they are sometimes called. 



The first of these is termed lynoratio Elenchi, because in 

 it, instead of proving the contradictory of the proposition ad- 

 vanced by your opponent (which, in order to refute him suc- 

 cessfully, you are bound to do, and which Aristotle called 

 Elenchus), you prove aome other proposition which, by more 

 or less resembling it, is likely to be mistaken for it. In doing 

 this, some one or more of the rules given by Logic fer proving 

 the contradictory of a given proposition will be violated. 



This is a fallacy which is very common in argument or con- 

 troversy ; and the particular manner in which the conclusion is 

 irrelevant i.e., fails to answer the purpose it is supposed to 

 answer varies with each particular case. Sometimes a parti- 



