27. Another locus for counter-argument is, where the definiend is Equivocal or Analogous, while one and the same definition is made to apply to all its distinct meanings. Such a definition, pretending to fit all, will in reality fit none; nothing but an univocal term can come under one and the same definition. It is wrong to attempt to define an equivocal term.[317] When its equivocation is not obvious, the respondent will put it forward confidently as univocal; while you as assailant will expose the equivocation. Sometimes, indeed, a respondent may pretend that an univocal word is equivocal, or that an equivocal word is univocal, in the course of the debate. To obviate such misconception, you will do well to come to an agreement with him prior to the debate, or to determine by special antecedent reasonings what terms are univocal or equivocal; for at that early stage, when he does not foresee the consequence of your questions, he is more likely to concede what will facilitate your attack. In the absence of such preliminary agreement, if the respondent, when you have shown that his bad definition will not apply universally, resorts to the pretence that the definiend, though really univocal, is equivocal, you will press him with the true definition of the part not included under his definition, and you will show that this true definition suits also for the remaining parts of the definiend. You will thus confute him by showing that, upon his original hypothesis, it must follow that there are two distinct definitions for the same definiend — the bad one which he has given, and the true one which you have constrained him to admit.[318] Perhaps, however, the term which he has undertaken to define may be really equivocal, and therefore indefinable; nevertheless, when you have shown the insufficiency of his definition, he may refuse to admit that the term is equivocal, but will deny a portion of its real meaning. You will then remind him that, as to the meaning of names, we must recognize tradition and custom without presuming to disturb it; but that, when we combine these names in our own discourse, we must beware of those equivocations which mislead the multitude.[319]
[317] Ibid. a. 23-37: ἔτι εἰ τῶν καθ’ ὁμωνυμίαν λεγομένων ἕνα λόγον ἁπάντων κοινὸν ἀπέδωκεν. — ἀλλ’ οὐδὲν ἧττον, εἰ ὁποτερωσοῦν πεποίηκεν, ἡμάρτηκεν.
Aristotle here cites and censures the definition of life given by a philosopher named Dionysius; he remarks that life is an equivocal term, having one meaning in animals, another and a different one in plants. Dr. Whewell has remarked that even at the present day a good definition of life is matter of dispute, and still a desideratum with philosophers.
Mr. John S. Mill adverts, in more than one portion of his ‘System of Logic’ (Bk. IV. ch. iii. s. 5, p. 222, seq.; Bk. V. ch. v. s. 8, p. 371), to the mistake and confusion arising from attempts to define Equivocal Terms. “The inquiries of Plato into the definitions of some of the most general terms of moral speculation, are characterized by Bacon as a far nearer approach to a true inductive method than is elsewhere to be found among the ancients, and are, indeed, almost perfect examples of the preparatory process of comparison and abstraction; but, from being unaware of the law just mentioned, he often wasted the powers of this great logical instrument on inquiries in which it could realize no result, since the phenomena, whose common properties he so elaborately endeavoured to detect, had not really any common properties. Bacon himself fell into the same error in his speculations on the nature of heat, in which he evidently confounded, under the name hot, classes of phenomena which had no property in common.� — “He occasionally proceeds like one who seeking for the cause of hardness, after examining that quality in iron, flint, and diamond, should expect to find that it is something that can be traced also in hard water, a hard knot, and a hard heart.�
[318] Topic. VI. x. p. 148, a. 37, seq. ἐπεὶ δ’ ἔνια λανθάνει τῶν ὁμωνύμων, ἐρωτῶντι μὲν ὡς συνωνύμοις χρηστέον, αὐτῷ δ’ ἀποκρινομένῳ διαιρετέον. ἐπεὶ δ’ ἔνιοι τῶν ἀποκρινομένων τὸ μὲν συνώνυμον ὁμώνυμόν φασιν εἶναι, ὅταν μὴ ἐφαρμόττῃ ἐπὶ πᾶν ὁ ἀποδοθεὶς λόγος, — προδιομολογητέον ὑπὲρ τῶν τοιούτων ἢ προσυλλογιστέον ὅτι ὁμώνυμον ἢ συνώνυμον, ὁπότερον ἂν ᾖ· μᾶλλον γὰρ συγχωροῦσιν οὐ προορῶντες τὸ συμβησόμενον.
These counsels of Aristotle are remarkable, as bearing on the details, and even the artifices, of dialectical debate.
[319] Topic. VI. x. p. 148, b. 16-22. ῥητέον πρὸς τὸν τοιοῦτον ὅτι τῇ μὲν ὀνομασίᾳ δεῖ χρῆσθαι τῇ παραδεδομένῃ καὶ παρεπομένῃ καὶ μὴ κινεῖν τὰ τοιαῦτα, ἔνια δ’ οὐ λεκτέον ὁμοίως τοῖς πολλοῖς.
28. If the definiend, of which a definition is tendered to you, is a compound, you may subtract from this definition the definition of one of the parts of the definiend, and then examine whether the remainder will suit as a definition of the remaining part of the definiend. If the remainder should not suit, this will show that the entire definition tendered is not tenable. Thus, if the definiend be a finite straight line, and if the definition tendered be, It is the boundary of a finite plane, of which (boundary) the middle covers or stands in the way of the extremities; you may subtract from this definition the definition of a finite line, viz., the boundary of a plane surface having boundaries, and the remainder of the definition ought then to suit for the remainder of the definiend. Now the remainder of the definiend is — straight; and the remainder of the definition is — that of which the middle covers or stands in the way of the extremities. But these two will not suit; for a line may be straight, yet infinite, in which case it will have neither middle nor extremities. Accordingly, since the remainder of the definition will not suit for the remainder of the definiend, this will serve as an argument that the entire definition tendered is not a good one.[320]
[320] Topic. VI. xi. p. 148, b. 23-32.
If the definiend be a compound, and if the definition contain no greater number of words than the definiend, the definition must be faulty; it will be nothing better than a substitution of words. Still more faulty will it be, if it substitutes rare and strange words in place of others which are known and familiar; or if it introduces a new word which signifies something different from that which it replaces.[321]