[206] Ibid. b. 15: ὁ μὴ γὰρ εἰδὼς εἰ τῷδ’ ὑπάρχει, οὐδ’ εἰ τῷδ’ ὑπάρχει μόνῳ γνωριεῖ.
[207] Topic. V. ii. p. 129, b. 21-29.
A second condition of its being well set out is, that it shall contain neither equivocal term nor equivocal or amphibolical proposition. Thus, if the thesis declares, To perceive is the proprium of an animal, it is equivocal; for it may mean either to have sensible perception, or to exercise sensible perception actually. You may apply the test to such a thesis, by syllogizing from one or both of these equivocal meanings. The respondent will make good his defence, if he shows that there is no such equivocation: as, for example, if the thesis be, It is a proprium of fire to be the body most easily moved into the upper region; where there is no equivocation, either of term or proposition.[208] Sometimes the equivocation may be, not in the name of the proprium itself, but in the name of the subject to which it is applied. Where this last is not unum et simplex but equivocal, the thesis must specify which among the several senses is intended; and, if that be neglected, the manner of setting out is incorrect.[209]
[208] Ibid. b. 30-p. 130, a. 13.
[209] Ibid. p. 130, a. 15-28.
Another form of the like mistake is, where the same term is repeated both in the predicate and in the subject; which is often done, both as to Proprium and as to Definition, though it is a cause of obscurity, as well as a tiresome repetition.[210] The repetition may be made in two ways: either directly, by the same term occurring twice; or indirectly, when the second term given is such that it cannot be defined without repeating the first. An example of direct repetition is, Fire is a body the rarest among bodies (for proprium of fire). An example of indirect repetition is, Earth is a substance which tends most of all bodies downwards to the lowest region (as proprium of earth); for, when the respondent is required to define bodies, he must define them — such and such substances.[211] An example free from objection on this ground is, Man is an animal capable of receiving cognition (as proprium of man).
[210] Ibid. a. 30-34. ταράττει γὰρ τὸν ἀκούοντα πλεονάκις λεχθέν — καὶ πρὸς τούτοις ἀδολεσχεῖν δοκοῦσιν.
[211] Ibid. a. 34-b. 5. ἕν γὰρ καὶ ταὐτόν ἐστι σῶμα καὶ οὐσία τοιαδί· ἔσται γὰρ οὗτος τὸ οὐσία πλεονάκις εἰρηκώς.
Another mode of bad or incorrect setting out is, when the term predicated as proprium belongs not only to the subject, but also to all other subjects. Such a proposition is useless; for it furnishes no means of discriminating the subject from anything; whereas discrimination is one express purpose of the Proprium as well as of the Definition.[212] Again, another mode is, when the thesis declares several propria belonging to the same subject, without announcing that they are several. As the definer ought not to introduce into his definition any words beyond what are required for declaring the essence of the subject, so neither should the person who sets out a proprium add any words beyond those requisite for constituting the proprium. Thus, if the thesis enunciates, as proprium of fire, that it is the thinnest and lightest body, here are two propria instead of one. Contrast with this another proprium, free from the objection just pointed out — Moist is that which may assume every variety of figure.[213]
[212] Topic. V. ii. p. 130, b. 12: ἀχρεῖον γὰρ ἔσται τὸ μὴ χωρίζον ἀπό τινων, τὸ δ’ ἐν τοῖς ἰδίοις λεγόμενον χωρίζειν δεῖ, καθάπερ καὶ τὰ ἐν τοῖς ὅροις.