Chapter 17

Predication of the essence of a thing is one thing, whereas that of its sort is another. Predication is of the essence of a thing when, being asked what a man is, we reply: ‘an animal.’ But it is of its sort when, being asked what sort of an animal, we answer: ‘a rational mortal animal.’ Thus, the genus and the species are predicated of the essence of a thing; whereas the difference, whether essential—that is to say, whether property or accident—is predicated of its sort. The individual substance neither signifies what the thing is nor of what sort it is, but it does signify which one it is. Thus, when we are asked who this man is, we reply that he is Peter. Then, when asked what sort of man he is, we reply that he is tall, let us say, or short.

(Moreover, one should know that things which differ in nature are said to be one thing and another. Thus, we say that man is one thing and the horse another, and we mean another thing in nature, because the species of man is one thing and that of the horse is something else. Those things, however, which differ in number, that is to say, which are individual substances, are said to be one and another. Thus, we say that Peter is one and Paul another. However, we cannot say that Peter is one and Paul another, because, if we did, we should not be telling the truth. For in nature they are one thing, but numerically they are not.

And one should know that the substance is called another thing, and likewise the essential differences, while the accident is called something of another sort. This is because the essential differences are considered in connection with the species, that is to say, in connection with the nature which they go to make up. The accident is considered in connection with the individual, because the accidents are constituent of the individual substance. A man, then, is one thing and a horse another, but Peter is of one sort and one and Paul of another sort and another. Moreover, every difference, whether essential or not, makes for something else of a different sort, for ἑτεροῖον means both something else and a thing of a different sort. The nature, then, signifies what a thing is, whereas the individual substance specifies this certain person or thing and every difference shows of what sort something is.)

{Περὶ τῆς ἐν τῷ τί ἐστι καὶ τῆς ἐν τῷ ποῖόν τί ἐστι κατηγορίας.} Ἐν τῷ τί μέν ἐστι κατηγορία ἐστὶν ἡ τῶν γενῶν κατὰ τῶν εἰδῶν αὐτῶν κατηγορία τουτέστιν ἡ τὸ τί ἐστι τὸ ὑποκείμενον σημαίνουσα καὶ ἡ τῶν εἰδῶν δὲ κατὰ τῶν ἀτόμων αὐτῶν: ἐρωτώμενοι γὰρ ‘τί ἐστιν ἄνθρωπος’ λέγομεν ‘ζῷον’ καὶ ἐρωτώμενοι ‘τί ἐστι Πέτρος’ λέγομεν ‘ἄνθρωπος’. Ἡ δὲ ἐν τῷ ποῖόν τί ἐστι κατηγορία ἐστὶν ἡ τῶν διαφορῶν κατὰ τῶν εἰδῶν, οἷς ἐνυπάρχουσι, καὶ τῶν συμβεβηκότων κατὰ τῶν ἀτόμων, οἷς ἐνυπάρχουσι, τουτέστιν ἡ τὸ ποῖόν τί ἐστι τὸ ὑποκείμενον σημαίνουσα: ἐρωτώμενοι γὰρ ‘ὁποῖον ζῷον ὁ ἄνθρωπος’ φαμὲν ‘λογικὸν θνητόν’. Τὸ δὲ λογικὸν καὶ τὸ θνητὸν διαφοραί εἰσιν οὐσιώδεις. Πάλιν ἐρωτώμενοι ‘ὁποῖος ἄνθρωπός ἐστιν ὁ Πέτρος’ φαμὲν ‘μακρὸς τυχὸν ἢ κολοβὸς ἢ σιμὸς ἢ γρυπός’. Τὸ δὲ διὰ τί ἐστι σημαίνει τὸ τέλος ἤγουν τὴν αἰτίαν, δι' ἣν τὸ ζητούμενον γέγονεν: ἐρωτώμενοι γὰρ ‘διὰ τί κλίνη’ φαμὲν ‘διὰ τὴν τῶν ἀνθρώπων ἀνάπαυσιν’.