Page images

consist either in a false judgment or a false inference. But, it will be remembered, the terms judgment and inference in the logical sense denote, the one intuitive judgment, and the other illative inference. Hence, when we speak of a false judgment or inference, we do not mean a real judgment or inference that is untrue (which would involve a contradiction of terms), but as when we speak of a false propheta pretended or simulated judgment or inference that is not really such.

$129. CLASSIFICATION OF FALLACIES.All fallacies must consist in the violation of some one or more of the rules of Logic, and hence may be correspondingly classified. Such a classification has, indeed, already been substantially effected in our statement of the logical rules; where, under each rule, the corresponding fallacies have been named. It remains, therefore, only to arrange them in convenient order, which is done in the table that follows:

Table of Fallacies


I. Illicit Premises.

(1) Fallacies in Definition.

Nonsense (or Non-Significance).

False Definition.

(2) Illicit Assumption of Premise (Petitio


II. Mistaking the Issue, o irrelevant Conclusion (Ignoratio Elenchi).


I. Illicit Conversions of Propositions. II. Illicit Substitutions of Terms; Scil. (1) Of Vocal Signs, or Vocables.



(2) Of Notions, i. e., of Senses of Terms (Equivocation, Homonymia et Amphibolia).

$132. OBSERVATIONS ON THE FALLACIES. -Of the two principal kinds of fallacies contained in the above table, the first-excepting the Fallacy of Irrelevant Conclusion-consist in the illicit assumption of the propositions to be used as the premises of ratiocination. But false or nonsensical propositions do not of themselves constitute fallacies, but only by reason of their use as judgments; for, according to our definition, a fallacy is a false semblance of ratiocination, and therefore cannot exist except as part of ratiocination. Hence we are not concerned with the truth or falsity or the absurdity of any proposition that may be asserted by any one, unless it be used as an independent judgment or as the premise of an

argument, in which case its pretensions may be examined, and, if found to be baseless, it may be challenged as illicit.

Where such an assumed premise is either non-significant or involves a false definition, it is in itself a fallacy, and therefore entitled to an independent rank as such. But such fallacies are innocuous if the sense of the terms be preserved unaltered throughout the ratiocination. For all conclusions in which they are involved must necessarily be without significance, or, in other words, nonsensical, and hence unsusceptible of use. But, as will be seen at large as we proceed, the conclusions from such premises, being in themselves unsusceptible of use, are invariably used as equivalent to other and significant propositions, and thus inevitably result in the Fallacy of Irrelevant Conclusion, or Ignoratio Elenchi, which consists in substituting for the conclusion another proposition (i. e., the true thesis); and which, though for convenience treated separately, may itself always be resolved into the Fallacy of Illicit Substitution, i. e., into an illicit conversion, or an illicit substitution of a term. And the same observation is true generally, though not universally, of illicit assumptions of false premises. These, if regarded as mere hypotheses, and if no misuse be made of the conclusion, are not illegitimate; but, it will

be seen, a conclusion deduced from such premises almost invariably either comes in conflict with some inconsistent fact, or otherwise fails to be sufficient for the purposes the reasoner has in view; and thus, almost inevitably, it is treated as equivalent to some other proposition, thus again presenting a case of Ignoratio Elenchi. Hence-if, as we conveniently may, we regard all assumed propositions as mere hypotheses, and therefore as not illegitimate, unless an ill use be made of the conclusionall illicit assumptions of premises must necessarily result in an Ignoratio Elenchi; which, as we have observed, must necessarily consist either in an illicit conversion or the illicit substitution of a term. Hence, as all valid ratiocination consists in the substitution of equivalent (§ 78), so all fallacy must consist in the substitution of non-equivalent terms.

Hence the simplest and most scientific classification of fallacies would be to regard them all as species of illicit substitution-that is to say, as cases, either of illicit conversion of propositions or illicit substitution of terms; and that we have adopted a different mode of classification is due simply to the consideration that we may thus more conveniently exhibit the different sources of fallacy. Hence, as we proceed, it will be found that the several fallacies all have a tendency, as it were, to run

into each other; which mainly results from the fact that they are all in their essential nature the same, differing only in the peculiar sources in which they originate; though partly also from the fact that, in general, fallacious arguments are not explicit, and the fallacy may vary according to the manner in which we may express them.

In our classification of the fallacies we have distinguished as a class the fallacy of "Mistaking the Issue, or Irrelevant Conclusion," thus apparently including two separate fallacies. But this is only apparently so. For unless there be some fault in the inference which would constitute another kind of fallacy -the conclusion and the premises must necessarily correspond, and we may therefore regard either the illicit assumption or the illicit conclusion as constituting the fallacy. If we regard the latter as the fallacy, it necessarily resolves itself into a case of illicit substitution. But, for convenience, we regard it as relating to the premises, and thus regarded, it consists in the illicit assumption of one proposition in place of another-i. e., of the actual premise for some other proposition more or less resembling it which is admitted.

In concluding these introductory observations I would refer the student to what is said in the conclusion of the Introduction, and

« PreviousContinue »