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CHAPTER THIRTEENTH.

PRACTICAL DIRECTIONS IN REASONING.

§. 295. Rules relating to the practice of reasoning.

VARIOUS directions have been given by writers on Logic, (which, it may be remarked here, is only another name for whatever concerns the nature, kinds, and applications of reasoning,) the object of which is to secure the more prompt, accurate, and efficient use of the reasoning power. It is but natural to suppose, that some of these dialectical rules are of greater, and others of less value. Such as appeared to be of the least questionable importance are brought together, and explained in this chapter; nor will this occasion any surprise, when it is recollected, that it has been the object of this Work throughout, not only to ascertain what the mental operations are, but by practical suggestions from time to time, to promote what is of a good, and prevent what is of a hurtful tendency in such operations.

The directions now referred to have of course a more intimate connection with Moral, than with Demonstrative reasoning; but this is a circumstance, which enhances, rather than diminishes their worth. The occasions, which admit and require the application of moral reasoning, being inseparable from the most common occurences and exigencies of life, are much more numerous, than those of demonstrative reasoning.

I.

§. 296. Of being influenced in reasoning by a love of the truth. The first direction in relation to reasoning, which will be given, concerns the feelings, with which it is proper to be animated. It is this. In all questions, which admit of

discussion, and on which we find ourselves at variance with the opinions of others, we are to make truth our object.-The opposite of a desire of the truth is a wish to decide the subject of dispute in one way rather than another, independently of a just consideration of the evidence. The foundation of such a preference of one result to another are in general the prejudices of interest and passion; and these are the great enemies of truth. Whenever we are under their influence, we form a different estimation of testimony and of other sources of evidence from what we should do under other circumstances; and at such times they can hardly fail to lead us to false results.This rule is important on all occasions of reasoning whatever, but particularly in public debate; because at such times the presence of others and the love of victory combine with other unpropitious influences to induce men to forget or to disregard the claims, which truth is always entitled to enforce.

§. 297. Care to be used in correctly stating the subject of discussion.

II. Another rule in the prosecution of an argument is, that the question under debate is to be fairly and correctly stated. The matter in controversy may be stated in such a way as to include, in the very enunciation of it, something taken for granted, which must necessarily lead to a decision in favor of one of the opponents. But this amounts to begging the question, a species of fallacy or sophism, upon which we shall again have occasion to remark.Sometimes the subject of discussion is stated so carelessly, that the true point at issue is wholly left out. It may be proper, therefore, in many cases to adopt the practice of special pleaders, and first to ascertain all the points, in which the opponents agree, and those in which they differ. And then they can hardly fail of directing their arguments to what is truly the subject of contention.

In order that there may not be a possibility of misunderstanding here, dialecticians should aim to have clear ideas of every thing stated in the question, which has an intimate connection with the point at issue. Subordinate parts of the question and even particular words are to be examined. If, for instance, the statement affirm or deny any thing, in re

gard to the qualities or properties of material bodies, it is incumbent upon us to possess as clear ideas as possible, both of the object in general, and of those properties or qualities in particular. Similar remarks will apply to other subjects of inquiry of whatever kind.

§. 298. Consider the kind of evidence applicable to the subject.

III. As one subject clearly admits of the application of one species of evidence, while another as clearly requires evidence of a different kind, we are thence enabled to lay down this rule, viz., We are to consider what kind of evidence is appropriate to the question under discussion.

When the inquiry is one of a purely abstract nature, and all the propositions, involved in the reasoning, are of the same kind, then we have the evidence of Intuition or intuitive perception; and the conclusion, for reasons already mentioned, is certain.In the examination of the properties of material bodies, we depend originally on the evidence of the Senses, which gives a character and strength to our belief according to the circumstances, under which the objects are presented to them. In judging of those facts in events and in the conduct of men, which have not come under our own observation, we rely on Testimony. This source of belief causes probability in a greater or less degree, according as the testimony is from one or more, given by a person, who understands the subject, to which it relates, or not, &c.And again, some subjects admit of the evidence of Induction, and in respect to others we have no other aids, than the less authoritative reasonings from Analogy. In other cases, the evidence is wholly made up of various incidental circumstances, which are found to have relation to the subject in hand, and which affect the belief in different degrees and for various causes.

And hence as the sources of belief, as well as the belief itself, have an intimate connection with the subject before us, they ought to be taken into consideration. The evidence should be appropriate to the question. But if the question admit of more than one kind of evidence, then all are entitled to their due weight.

§. 299. Reject the aid of false arguments or sophisms.

IV. There is a species of false reasoning, which we call a SOPHISM, A sophism is an argument, which contains some secret fallacy, under the general appearance of correctness. The aid of such arguments, which are calculated to deceive, and are, in general, inconsistent with a love of the truth, should be rejected.

(1) IGNORATIO ELENCHI, or misapprehension of the question, is one instance of sophism. It exists when, from some misunderstanding of the terms and phrases that are employed, the arguments advanced do not truly apply to the point in debate. It was a doctrine, for instance, of some of the early philosophic teachers of Greece, that there is but one principle of things. Aristotle, understanding by the word principle what we commonly express by the word ELEMENT, attempted to show the contrary, viz, that the elements are not one but many, thus incurring the imputation of IGNORATIO ELENCHI; for those, who held the doctrine, which was thus subjected to his animadversion, had reference not to the forms but the cause of things, not to any doctrine of elementary material particles, but to the intellectual origin, the creative mind, the Supreme Being, whom as the PRInciple, (that is, as the beginning and the support of things,) they maintained to be one.*

(2) PETITIO PRINCIPII, or begging of the question, is another instance of sophism. This sophism is found, whenever the disputant offers, in proof of a proposition, the proposition itself in other words. The following has been given as an instance of this fallacy in reasoning ;-A person attempts to prove that God is eternal, by maintaining, that his existence is without beginning and without end. Here the proof, which is offered, and the proposition itself, which is to be proved, are essentially the same. When we are told, that opium causes sleep, because it has a soporific quality, or that grass grows by means of its vegetative power, the same thing is repeated in other terms.This fallacy is very frequently practised; and a little care in detecting it would spoil many a fine saying, as well as deface many an elaborate argument. What is called arguing in a circle is a species of sophism very * La Logique ou L'art de Penser, (Port Royale,) Part III, Chap. XIX.

nearly related to the above. It consists in making two propositions reciprocally prove each other.

(3) NON CAUSA PRO CAUSA, or the assignation of a false cause. People are unwilling to be thought ignorant; rather than be thought so, they will impose on the credulity of their fellow men, and sometimes on themselves, by assigning false causes of events. Nothing is more common, than this sophism among illiterate people; pride is not diminished by deficiency of learning, and such people, therefore, must gratify it, by assigning such causes of events as they find nearest at hand. Hence, when the appearance of a comet is followed by a famine or a war, they are disposed to consider it as the cause of those calamities. If a person have committed some flagrant crime, and shortly after suffer some heavy distress, it is no uncommon thing to hear the former assigned, as the direct and the sole cause of the latter.-This was the fallacy, which historians have ascribed to the Indians of Paraguay, who supposed the baptismal ceremony to be the cause of death, because the Jesuit missionaries, whenever opportunity offered, administered it to dying infants, and to adults in the last stage of disease.

(4) Another species of sophistry is called FALLACIA ACCIDENTIS.-We fall into this kind of false reasoning, whenever we give an opinion concerning the general nature of a thing from some accidental circumstance. Thus the Christian religion has been made the pretext for persecutions, and has in consequence been the source of much suffering; but it is a sophism to conclude, that it is, on the whole, not a great good to the human race, because it has been attended with this perversion. Again, if a medicine have operated in a particular case unfavorably, or, in another case, have operated very favorably, the universal rejection or reception of it, in conséquence of the favorable or unfavorable result in a particular instance, would be a hasty and fallacious induction of essentially the same sort. That is, the general nature of the thing is estimated from a circumstance, which may be wholly accidental.

§. 300. Fallacia equivocationis or the use of equivocal terms and phrases. V.It is a further direction of much practical importance, that the reasoner should be careful, in the use of lan

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