[213] Ibid. b. 23-37.
A farther mistake is, when the predicate declaring the proprium includes either the subject itself or some species comprehended under the subject; for example, when we are told, as a proprium of animal, that animal is a substance of which man is a species. We have already seen that the proprium ought to be better known than its subject; but man is even less known (posterior in respect to cognition) than animal, because it is a species under the genus animal.[214]
[214] Ibid. iii. p. 130, b. 38.
Again, our canon — That the Proprium should be better known than its subject, or should make the subject better known — will be violated in another way, if the proprium enunciated be something opposite to the subject, or in any other way simul naturâ as compared with the subject; and still more, if it be posterius naturâ as compared with the subject. Thus, if a man enunciates, as proprium of good, that good is that which is most opposite to evil, his proprium will not be well or correctly set out.[215]
[215] Ibid. p. 131, a. 12-26. This locus is not clear or satisfactory, as Alexander remarks in Scholia (p. 284, b. 12-23, Br.). He says that it may pass as an ἔνδοξον — something sufficiently plausible to be employed in Dialectic. In fact, Alexander virtually controverts this locus in what he says a little farther down (Schol. p. 285, a. 31), that the Proprium is always simul naturâ with its subject.
Perhaps, again, the thesis may enunciate as proprium what is not constantly appurtenant to the subject, but is sometimes absent therefrom; or, intending to enunciate an occasional proprium, it may omit to specify the qualifying epithet occasional. In either case the proprium is not well set out, and a ground is furnished for censure, which ought always to be avoided.[216]
[216] Topic. V. iii. p. 131, a. 27-b. 18. οὐκ ἔσται καλῶς κείμενον τὸ ἴδιον — οὔκουν δοτέον ἐστὶν ἐπιτιμήσεως σκῆψιν.
Moreover, the proprium will not be well set out, if it be such as does not necessarily belong to the subject, but is only shown by the evidence of sense to belong thereunto. In this case, when the subject is out of the reach of sensible perception, no one knows whether the supposed proprium still continues as its attribute. Thus, suppose the thesis to enunciate as a proprium of the sun, that it is the brightest star borne in movement above the earth: the fact that it is so borne in movement above the earth is one that we know by sensible perception only; accordingly, after the sun sets and we cease to see it, we cannot be sure that it continues to be borne in movement. If a proprium knowable as such by sense be chosen, it ought to be one which is also knowable independently, as belonging to the subject by necessity. Thus, if a man enunciates, as proprium of superficies, that superficies is what first becomes coloured or first receives colour, this is a proprium well set out. For we know clearly that it must always belong to a superficies; though we may also obtain the additional evidence of sense, by looking at some perceivable body.[217]
[217] Ibid. b. 19-36. οἷον ἐπεὶ ὁ θέμενος ἐπιφανείας ἴδιον ὃ πρῶτον κέχρωσται, αἰσθητῷ μέν τινι προσκέχρηται τῷ κεχρῶσθαι, τοιούτῳ δ’ ὃ φανερόν ἐστιν ὑπάρχον ἀεί, εἴη ἂν κατὰ τοῦτο καλῶς ἀποδεδομένον τὸ τῆς ἐπιφανείας ἴδιον.
Aristotle means that we know clearly, by evidence independent of sense, that the superficies must be the first portion of the body that becomes coloured, though we may attain the additional evidence of our senses (προσκέχρηται) to the same fact.