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tinction; as, if any one should reason thus; All the musical instruments of the Jewish temple made a noble concert; the harp was a inusical instrument of the Jewish temple; therefore the harp made a noble concert. Here the word all in the major is collective, whereas such a conclusion requires that the word all should be distributive.
It is the same fallacy when the universal word all or no refers to species in one proposition, and to individuals in another; as, All animals were in Noah's ark; therefore no animals per rished in the flood; whereas in the premise all animals signifies every kind of animals, which does not exclude or deny the drowning of a thousand individuals.
VIII. The last sort of sophisms arises from our abuse of the ambiguity of words, which is the largest and most extensive kind of fallacy; and indeed several of the former fallacies might be reduced to this head.
When the words or phrases are plainly equivocal, they are called sophisms of equivocation ; as if we should argue thus : He that sends forth a book into the light desires it to be read; he that throws a book into the fire, sends it into the light; therefore he that throws a book into the fire desires it to be read.
This sophism, as well as the foregoing, and all of the like nature, are solved by shewing the different senses of the words, terms or phrases. Here light in the major proposition signifies the public view of the world ; in the minor it signifies the brightress of flame and fire; and therefore the syllogism has four terms, or rather it has no middle term, and proves nothing.
But where such gross equivocations and ambiguities appear in arguments, there is little danger of imposing upon ourselves or others. The greatest danger, and which we are perpetually exposed to in reasoning, is, where the two senses or significations of one term are near a-kin, and not plainly distinguished, and yet they are really sufficiently different in their sense to lead us into great mistakes, if we are not watchful. And indeed the greatest part of controversies in the sacred or civil life, arise from the different senses 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 terins.
There is after all these, another sort of sophisin which is wont tų be called an imperfect enumeration or a false induction, when frein a few experiments or observations men infer general theorens and universal propositions. But this is sufficiently noticed in the foregoing chapter, where we treated of that sort of syllogisin which is called induction.
Sect. II.-Two general 'Tests of true Syllogisms, and Methods
of solving all Sophisms. BESIDES 'the special description of true syllogisms and sophisms already given, and the rules by which the one are framed, and the other refuted, there are these two general methods of reducing all syllogisms wbatsoever to a test of their truth or falsehood.
I. The first is, that the “ premises must, at least implicitly, contain the conclusion ; or thus, one of the premises must con, tain the conclusion, and the other must shew that the conclusion is contained in it." The reason of this rule is this ; when any proposition is offered to be proved, it is necessary to find another proposition which confirms it, which may be called the containing proposition ; but because the second must not contain the first in an express manner, and in the same words*, therefore it is necessary that a third or ostensive proposition be found out, to shiew that the second proposition contains the first, which was to be proved. Let us make an experiment of this syllogisı :
" Whosoever is a slave to his natural inclinations is miserable ; the wicked man is a slave to his natural inclinations : therefore the wicked man is wiserable." Here it is evident that the major proposition contains the conclusion ; for under the general character of a slave to natural inclinations, a wicked man is contained or included; and the minor proposition declares it ; whence the conclusion is evidently deduced, that the wicked man is miserable.
In many affirmative syllogisms we may suppose either the major or the minor to contain the conclusion, and the other to ahew it; for there is no great difference. But in negative syllogisms it is the negative proposition that contains the conclusion, and the affirmative proposition shews it; as “ every wise man masters his passions; no angry man masters bis passions; therefore no angry man is wise.” Here it is more natural to suppose the minor to be the containing proposition; it is the minor implicitly denies wisdom concerning an angi'y man, because masiering the passions is included in wisdom, and the major shews it.
Note, This rule may be applied to complex and conjunctive, as well as simple syllogisms, and is adapted to shew the truth or falsehood of any of them.
II. The second is this ; “ As the terms in every syllogism are usually repeated twice, so they must be taken precisely in the same sense in both places :" for the greatest part of mistakes that arise in forming syllogisms, is derived from some little difference in the sense of one of the terms in the two parts, of the syllogism wherein it is used. Let us consider the following sophisms :
* It is confessed that conditional and disjunctive major propositions do ex pressly contain all that is in the conclusion; but then it is not in a certain an conclusive manner, but only io a dubious form of speech, and mingled - i other terms; and therefore it is not tbe same express proposition,
1. “ It is a sin to kill a man; a murderer is a man ; there. fore it is a sin to kill a murderer.” Here the word kill in the first proposition signifies to kill unjustly, or without law; in the conclusion it is taken absolutely for patting 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 map."
." This is a relative syllogism: 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 wbat I am; therefore you are not a man.” Here what I am in the major proposition is taken especially for my nature; but in the minor proposition the same words are taken individually for my person; therefore the inference must be false, for the syllogism does not take the term, what I am, both times in the same sense.
3.“ He that says you are an animal says true ; but he that says you are a goose, says you are an animal; therefore he that says you are a goose, says true.” In the major proposition the word animal is the predicate of an incidental proposition ; which incidental proposition being affirmative, renders the predicate of it particular, according to Chap. II. Sect. 2. Axiom 3. and consequently the word animal there signifies only human animality. In the major proposition the word animal, for the same reason, signifies the animality of a goose; whereby it becomes an ambiguous terin, and unfit to build the conclusion upon. Or if you say, the word animal in the minor, is taken for human animality, then the minor is evidently false.
It is from the last general test of syllogisms, that we de rive the custom of the respoudent in answering the arguments of the opponent, which is to distinguish upon the major or minor proposition, and declare whicb term is used in two senses, and in what sense the proposition may be true, and in what sense it is false...
CHAP. IV-Some general Rules to direct our Reasoning
* MOST of the general and special directions given to forin our judgments aright in the preceding part of Logic might be rehcarsed bere ; for the judgments which we pass upon things are generally built on some secret reasoning or argument by. which the proposition is supposed to be proved. But there way be
yet šome farther assistances given to our reasoning powers in their search after truth, and an observation of the following rules: will be of great importance for that ead.
I. “ Accustom yourselves to clear and distinct ideas, to evident propositions, to strong and convincing arguments." Converse much with those friends, and those books, and those parts of learning, where you meet with the greatest clearness of thought, and force of reasoning. The mathematical sciences, and particularly arithinetic, geometry, and mechanics, abound with these advantages : and if there were nothing valuable in them for the uses of human life, yet the very speculative parts of this sort of learning are well worth our study; for by perpetual examples they teach us to conceive with clearness, to connect our ideas and propositions in a train of dependence, to reason with strength and demonstration, and to distinguish between truth and falsehood. Something of these sciences should be studied by every man who pretends to learning, and that, as Mr. Locke expresses it, “not so much to make us mathemati cians, as to make us reasonable creatures.'
We should gain such a familiarity with evidence of perception and force of reasoning, and get such a habit of discerning clear truths, that the mind may be soon offended with obscurity and confusion : then we shall, as it were, naturally and with ease restrain our minds from rash judgment, before we attain just evidence of the proposition which is offered to us ; and we shall with the same ease, and as it were, naturally seize and embrace every truth that is proposed with just evidence.
This habit of conceiving clearly, of judging justly, and of reasoning well, is not to be attained merely by the happiness of constitution, the brightness of genius, the best natural parts, or the best collection of logical precepts. It is custom and practice that must form and establish this babit. 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 set of rules, any more than a good painter or musician may be formed extempore, by an excellent lecture on music 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 past it, it is no wonder that we should not learn good reasoning, any more than that an ignorant clown should not be able to learn fine language, dancing, or a courtly behaviour, when bis rustic airs have growu up with him till the age of forty.
For want of this care, some persons of rank and education dwell all their days among obscure ideas; they conceive and judge always in confusion, they take weak arguments for demonstration, they are led away with the disguises and shadows of truth. Now if such persons happen to have a bright imagination, a volubility of speech, and a copiousness of language, they not only impose many errors upon their own understandings, but
they stamp the image of their own mistakes upon their neighbours also, and spread their errors abroad.
It is a matter of just lamentation and pity, to consider the weakness of the common multitude of mankind in this respect, how they receive any thing into their assent upon the most trifling grounds. True reasoning bath very little share in forming their opinions. They resist the most conviocing arguments by an obstinate adherence to their prejudices, and believe the most improbable things with the greatest assurance. They talk of the abstrusest mysteries, and determine upon them with the utmost confidence, and without just evidence either from reason or revelation. A confused heap of dark and inconsistent ideas make up a good part of their knowledge in matters of philosophy as well as religion, having never been taught the use and value of clear and just reasoning.
Yet it must be still confessed that there are some mysteries in religion, both natural and revealed, as well as some abstruse points in philosophy, wherein the wise as well as the unwise must be content with obscure ideas. There are several things, especially relating to the invisible world, which are upsearchable in our present state, and therefore we must believe wbat revelation plainly dictates, though the ideas may be obscure. Reason itself demands this of us;. but we should seek for the brightest evidence both of ideas and of the connection of them, wheresoever it is attainable.
IĮ.“ Enlarge your general acquaintance with things daily, in order to attain a rich furniture of topics or middle terms, whereby those propositions which occur may be either proved or disproved ;" but especially meditate and enquire with great diligence and exactness into the nature, properties, circumstances, and relations of the particular subject about which you judge or argue. Consider its causes, effects, consequences, adjuncts, opposites, sigos, &c. so far as is needful to your present purpose. You should survey a question round about, and on all sides, and extend your views as far as possible, to every thing that has a connection with it. This practice has niany, advantages in it; as,
1. It will be a means to suggest to your mind proper topics for argument about any proposition that relates to the same subject. 2. It will enable you with greater readiness and justness of thought to give an answer to any sudden question upon that subject, whether it arises in your own mind, or is posed by others. 3. This will instruct you to give a plainer and speedier solution of any difficulties that may attend the theme of your discourse, and to refute the objections of those who have espoused a contrary opinion. 4. By such a large survey of the whole subject in all its properties and relations, you will be