propositions that they will be consistent with each other; and it is an almost equally universal characteristic of untrue propositions that they will be inconsistent with other propositions known to be true.

This is particularly the case in all the different branches of the Science of Human Nature; all of whose parts and particular principles are so connected by numerous relations that it is almost impossible to assert an untrue principle without coming in conflict with others that are self-evident, or readily demonstrable, and which have thus come to be universally admitted. Hence it may be said that in Morality or Politics we may set out from almost any principles, provided we hold them with indifference and are capable of abandoning them when shown to be inconsistent with settled principles and known facts. From which it may be inferred that the reductio ad absurdum in fact constitutes not only an efficient, but almost an all-sufficient, instrument for the detection of fallacy in Moral and Political Science.

General Examples

166. LOCKE'S THEORY OF SIMPLE IDEAS. -A most instructive example of Illicit Assumption of Premise occurs in the fundamental assumption of Locke's theory of knowledge;

which is, that the original notions received in the mind from sensible objects are notions of the qualities of substances, such as color, hardness, etc., which he calls simple ideas; and out of which, he holds, all our notions are compounded. But on reflection it will be perceived that the original or primordial notions of the mind are the composite notions of substances or things; and what Locke calls "simple notions" are the result of subsequent analysis.

§ 167. THE OBLIGATION OF CONTRACTS.It is one of the so-called maxims of the law that contracts are obligatory and ought to be enforced (Pacta quælibet servanda sunt); and this is commonly assumed as a universal proposition, as, e. g., by Bentham and Spencer in the examples given below (§§ 180, 181). But there are innumerable cases in which it is obviously not right that contracts should be enforced, and in which, in fact, the law does not enforce them; which is an effectual refutation of the principle. The true principle is that in case of breach of contract the injured party is entitled to compensation-as in the case of torts-for the detriment suffered by him by the acts of the wrongdoer (i. e., by the making of the contract and its breach).

168. FALSE ASSUMPTION OF FACT.-This includes innumerable cases, which it would be impossible to classify. One of the most in

teresting is furnished by Tacitus in his account of the mutiny of the Pannonian legions on the accession of Tiberius,-in the address of the soldier, Vibulenus, to the general, Bloesus. His brother, he said, coming as a delegate from the German army, had been butchered by the commands of Bloesus. "Answer, Bloesus," he said; "where hast thou thrown away his corpse?" By which, says Tacitus, he raised such a spirit of frenzy and vengeance that had it not been quickly manifested that there was no corpse to be found

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and that Vibulenus never had any brother, they had gone nigh to sacrifice the general." The example, so far as Vibulenus is concerned, was simply a lie, but, in the soldiers, a fallacy that would have been readily refuted by apply. ing the test of the onus probandi.

CHAPTER XII

MISTAKING THE ISSUE, AND IRRELEVANT CONCLUSION (IGNORATIO ELENCHI)

§ 169. The nature of this fallacy, which is explained under Rule IV. of the Rules of Logic, is precisely expressed by the first of the names we have given it, which is a technical term taken from the law. This differs from the equally appropriate term Irrelevant Conclusion only in this, that the former has regard to the origin, the latter to the outcome of the fallacy. Or, in other words, when we regard the beginning of the fallacy, we call it Mistaking the Issue; when the end, Irrelevant Conclusion; and, in either case, Ignoratio Elenchi. The two names, i. e., Mistaking the Issue and Irrelevant Conclusion, present, therefore, two different aspects of the same fallacy, under each of which it will be convenient to consider it.

$ 170. MISTAKING THE ISSUE.-This, as is well appreciated by the lawyers, is one of the most formidable and most common of all fal

lacies.

For the most fruitful of all sources of fallacy is bias or logical dishonesty, of which the expedient of mistaking or misstating the question at issue is one of the most obvious and most potent instrumentalities. And as logical honesty is, in fact, one of the rarest of intellectual virtues, it can be readily understood that the fallacy must be common.

171. FALLACY OF SEVERAL QUESTIONS OR ISSUES.-One form of this fallacy may be identified with the technical Fallacia plurium interrogationum (§ 197), which consists in mixing in one several questions or issues. As defined by Aristotle, it results "from making two questions one, when it escapes notice that there are many, and one answer is given, as if there was one question only."

The following examples are taken from a recent work:

"Did you steal anything when you broke into my house last night?' Are you the only rogue in your family?' 'Have you quit drinking? Have you cast your horns?' (Hence sometimes called Cornutus.)"-(Davis, Theory of Thought, 294.)

The fallacy is readily solved by separating the compound question into its several components,-as, e. g., in the following: Menedemus, Alexino rogante, Numquid, patrem verberare desiisset? inquit, Nec verberavi, nec desii; or,