6. The sixth head of Fallacy — Non Causa pro Causâ — is, when we mistake for a cause that which is not really a cause; or, to drop the misleading word cause, and to adopt the clearer terms in which this same fallacy is announced in the Analytica Priora[35] — Non per Hoc — Non propter Hoc, it arises when we put forward, as an essential premiss of a given conclusion, something that is not really an essential premiss thereof. When you intend to refute a given thesis by showing, that, if admitted, it leads to impossible or absurd conclusions, you must enunciate that thesis itself among the premisses that lead to such absurdities.[36] But, though enunciated in this place, it may often happen that the thesis may be an unnecessary adjunct — not among the premisses really pertinent and essential: and that the impossible conclusion may be sufficiently proved, even though the thesis were omitted. Still, since the thesis is declared along with the rest, it will appear falsely to be a part of the real proof. It will often appear so even to yourself the questioner; you not detecting the fallacy.[37] Under such circumstances the respondent meets you by Non propter Hoc. He admits your conclusion to be impossible, and at the same time to be duly proved, but he shows you that it is proved by evidence independent of his thesis, and not by reason or means of his thesis. Accordingly you have advanced a syllogism good in itself, but not good for the purpose which you aimed at;[38] viz., to refute the thesis by establishing that it led to impossible consequences. You will fail, even if the impossible consequence which you advance is a proposition conjoined with the thesis through a continuous series of intermediate propositions, each of them having one common term with the next. Much more will you fail, if your impossible consequence is quite foreign and unconnected with the thesis; as we sometimes find in Dialectic.
[35] Ibid. b. 21; vii. p. 169, b. 13. Compare Analyt. Prior. II. xvii. p. 65.
In commenting on the above chapter of the Analytica Priora, I have already remarked (Vol. I. p. 258, [note]) how much better is the designation there given of the present fallacy — Non per Hoc (οὐ παρὰ τὴν θέσιν τὸ ψεῦδος) — than the designation here given of the same fallacy — Non Causa pro Causâ. Aristotle is speaking of a syllogistic process, consisting of premisses and a conclusion; the premisses being the reasons or grounds of the conclusion, not the cause thereof, as that term is commonly understood. The term cause is one used in so many different senses that we cannot be too careful in reasoning upon it. See Whately’s remarks on this subject, Bk. iii. Sect. 14, of his Logic: also his Appendix I. to that work, under article Reason.
[36] Soph. El. v. p. 167, b. 24: ἐὰν οὖν ἐγκαταριθμήθῃ ἐν τοῖς ἀναγκαίοις ἐρωτήμασι πρὸς τὸ συμβαῖνον ἀδύνατον, δόξει παρὰ τοῦτο γίνεσθαι πολλάκις ὁ ἔλεγχος.
[37] Ibid. b. 35: καὶ λανθάνει πολλάκις οὐχ ἧττον αὐτοὺς τοὺς ἐρωτῶντας τὸ τοιοῦτον.
[38] Ibid. b. 34: ἀσυλλόγιστοι μὲν οὖν ἁπλῶς οὐκ εἰσὶν οἱ τοιοῦτοι λόγοι, πρὸς δὲ τὸ προκείμενον ἀσυλλόγιστοι.
7. The seventh and last of these heads of Fallacy is, when the questioner puts two distinct questions in the same form of words, as if they were one — Fallacia Plurium Interrogationum ut Unius. In well-conducted Dialectic the respondent was assumed to reply either Yes or No to the question put; or, if it was put in the form of an alternative, he accepted distinctly one term of the alternative. Under such conditions he could not reply to one of these double-termed questions without speaking falsely or committing himself. Are the earth and the sea liquid? Is the heaven or the earth sea? The questions are improperly put, and neither admits of any one correct answer. You ought to confine yourself to one question at a time, with one subject and one predicate, making what is properly understood by one single proposition. The two questions here stated as examples ought properly to be put as four.[39]
[39] Ibid. b. 38-p. 168, a. 16; vi. p. 169, a. 6-12. ἡ γὰρ πρότασίς ἐστιν ἓν καθ’ ἑνός. — εἰ οὖν μία πρότασις ἡ ἓν καθ’ ἑνὸς ἀξιοῦσα, καὶ ἁπλῶς ἔσται πρότασις ἡ τοιαύτη ἐρώτησις.
The examples given of this fallacy by Aristotle are so palpable — the expounder of every fallacy must make it clear by giving examples that every one sees through at once — that we are tempted to imagine that no one can be imposed on by it. But Aristotle himself remarks, very justly, that there occur many cases in which we do not readily see whether one question only, or more than one, is involved; and in which one answer is made, though two questions are concerned. To set out distinctly all the separate debateable points is one of the most essential precautions for ensuring correct decision. The importance of such discriminating separation is one of the four rules prescribed by Descartes in his Discours de la Méthode. The present case comes under Mr. Mill’s Fallacies of Confusion.
Aristotle has thus distinguished and classified Fallacies under thirteen distinct heads in all — six In Dictione, and seven Extra Dictionem; among which last one is Ignoratio Elenchi. He now proceeds to show that, in another way of looking at the matter, all the Fallacies ranged under the thirteen heads, may be shown to be reducible to this single one — Ignoratio Elenchi. Every Fallacy, whatever it be, transgresses or fails to satisfy, in some way or other, the canons or conditions which go to constitute a valid Elenchus,[40] or a valid Syllogism. For a true Elenchus is only one mode of a true Syllogism; namely, that of which the conclusion is contradictory to some given thesis or proposition.[41] With this particular added, the definition of a valid Syllogism will also be the definition of a good Elenchus. And thus Ignoratio Elenchi — misconception or neglect of the conditions of a good Elenchus — understood in its largest meaning, is rather a characteristic common to all varieties of Fallacy, than one variety among others.[42]