[164] Ibid. a. 14-19.
[165] Ibid. iii. a. 20-26.
Again, the generic term and the specific term ought to be univocal in signification. You must examine (according to the tests indicated in the First Book of the Topica) whether it be taken equivocally in the thesis. If it be so, you have a ground of attack, and also if it be taken metaphorically; for every genus ought to be enunciated in the proper sense of the term, and no metaphor can be allowed to pass as a genus.[166] Note farther that every true genus has more than one distinct species. You will, therefore, examine whether any other species, besides the subject of the thesis, can be suggested as belonging to the predicate of the thesis. If none, that predicate cannot be the true genus of the subject.[167]
[166] Ibid. a. 27-37. σκοπεῖν δὲ καὶ εἰ τὸ μεταφορᾷ λεγόμενον ὡς γένος ἀποδέδωκεν, οἷον τὴν σωφροσύνην συμφωνίαν· πᾶν γὰρ γένος κυρίως κατὰ τῶν εἰδῶν κατηγορεῖται, ἡ δὲ συμφωνία κατὰ τῆς σωφροσύνης οὐ κυρίως ἀλλὰ μεταφορᾷ· πᾶσα γὰρ συμφωνία ἐν φθόγγοις.
[167] Topic. IV. iii. p. 123, a. 30.
Several loci are furnished by Contraries, either to the species or the genus. If there be something contrary to the species, but nothing contrary to the genus, then that which is contrary to the species ought to be included under the same genus as the species itself; but, if there be something contrary to the species, and also something contrary to the genus, then that which is contrary to the species ought to be included in that which is contrary to the genus. Each of these doctrines you will have to make good by induction of particular cases.[168] If that which is contrary to the species be a genus itself (e.g., bonum) and not included in any superior genus, then the like will be true respecting the species itself: it will not be included in any genus; and the predicate of the thesis will not be a true genus. Bonum and malum are not included in any common superior genus; each is a genus per se.[169] Or suppose that the subject (species) of the thesis, and the predicate (genus) of the thesis, have both of them contraries; but that in the one there is an intermediate between the two contraries, and in the other, not. This shows that the predicate cannot be the true genus of the species; for, wherever there is an intermediate between the two contraries of the species, there also is an intermediate between the two contraries of the genus; and vice versâ.[170] If there be an intermediate between the two contraries of the species, and also an intermediate between the two contraries of the genus, you will examine whether both intermediates are of like nature, designated by analogous terms. If it be not so (if, e.g., the one intermediate is designated by a positive term, and the other only by a negative term), you will have ground for contending against the thesis, that the predicate enunciated therein is not the true genus of the subject. At any rate, this is a probable (ἔνδοξον) dialectical argument — to insist upon analogy between the two intermediates; though there are some particular cases in which the doctrine does not hold.[171]
[168] Ibid. b. 1-8. φανερὸν δὲ τούτων ἕκαστον διὰ τῆς ἐπαγωγῆς.
[169] Ibid. b. 8-12.
[170] Topic. IV. iii. p. 123, b. 12, seq.
[171] Ibid. b. 17-23: ἔνστασις τούτου ὅτι ὑγιείας καὶ νόσου οὐδὲν μεταξύ, κακοῦ δὲ καὶ ἀγαθοῦ· ἢ εἰ ἔστι μέν τι ἀμφοῖν ἀνὰ μέσον, καὶ τῶν εἰδῶν καὶ τῶν γενῶν, μὴ ὁμοίως δέ, ἀλλὰ τῶν μὲν κατ’ ἀπόφασιν, τῶν δ’ ὡς ὑποκείμενον. ἔνδοξον γὰρ τὸ ὁμοίως ἀμφοῖν, καθάπερ ἐπ’ ἀρετῆς καὶ κακίας, καὶ δικαιοσύνης καὶ ἀδικίας· ἀμφοῖν γὰρ κατὰ ἀπόφασιν τὰ ἀνὰ μέσον.