Chapter 12

Difference and quality and property are all the same thing in relation to their subject, but in relation to their operation they are different. Thus, rationality is said to be both a quality and a property and a difference of man, but it is these, in different ways. Thus, on the one hand, in so far as it makes and, as it were, forms the substance, it is said to be a quality. Then, in so far as it becomes peculiar to this substance, it is said to be a property. But, in comparison with the irrational—an ox, say, or a mule, or a dog—then it is said to be a difference, because in it man differs from the irrational animals.

The term difference is used in three senses: in a common sense, in a special sense, and in a very special sense. For it is impossible to find any two things which do not differ from each other in something. Thus, in some things species differ from species; in others an individual substance differs from another of the same species and substance; and in others an individual substance differs from itself. For the species of man differs from that of the horse by the rational and the irrational, the rational and the irrational being said to constitute an essential difference. Similarly, all things by which species differs from species are called natural and essential and constituent and specific difference and quality (and a natural property, as inhering unchangeably in the whole species). This is called by the philosophers a very special difference, as being indicative of the nature and more proper to it. Again, a man differs from a man, or a horse from a horse, or a dog from a dog (that is, an individual differs from an individual of the same species), according as one is large and the other small, or as one is old and the other young (or as one is flat-nosed and the other sharp-nosed), or as one is intelligent and the other stupid. All these are called non-essential differences and qualities, which is precisely what an accident is, concerning which we shall speak directly.

[06] {Περὶ διαφορᾶς.} Αὕτη δὲ τριχῶς λέγεται, κοινῶς τε καὶ ἰδίως καὶ ἰδιαίτατα. Ἀδύνατον γὰρ μὴ διαφέρειν ἀλλήλων δύο τινὰ κατά τι. Ἄλλοις οὖν διαφέρει εἶδος εἴδους, καὶ ἄλλοις ὑπόστασις τῆς ὁμοειδοῦς καὶ ὁμοουσίου ὑποστάσεως καὶ ἄλλοις ὑπόστασις ἑαυτῆς. Διαφέρει μὲν γὰρ τὸ εἶδος τοῦ ἀνθρώπου τοῦ εἴδους τοῦ ἵππου κατὰ τὸ λογικὸν καὶ ἄλογον. Καὶ λέγεται τὸ λογικὸν καὶ ἄλογον οὐσιώδης διαφορά. Ὁμοίως καὶ πάντα, οἷς διαφέρει εἶδος εἴδους, φυσικὴ καὶ οὐσιώδης καὶ συστατικὴ διαφορὰ καὶ ποιότης λέγεται καὶ φυσικὸν ἰδίωμα, ὅπερ παντὶ τῷ εἴδει ἐνυπάρχει ἀπαραλλάκτως, ἥτις καλεῖται παρὰ τοῖς φιλοσόφοις ἰδιαίτατα διαφορὰ ὡς οἰκειοτέρα καὶ τῆς φύσεως παραστατική. Πάλιν διαφέρει ἄνθρωπος ἀνθρώπου ἢ ἵππος ἵππου ἢ κύων κυνός, τουτέστιν ἄτομον ὁμοειδοῦς ἀτόμου, καθὸ ὁ μέν ἐστι μακρὸς ὁ δὲ κολοβός, ὁ μὲν παλαιὸς ὁ δὲ νέος, ὁ μὲν σιμὸς ὁ δὲ γρυπός, ὁ μὲν φρόνιμος ὁ ἕτερος μωρός. Ταῦτα πάντα ἐπουσιώδεις διαφοραὶ καὶ ποιότητες λέγονται, ὅπερ ἐστὶ τὸ συμβεβηκός, περὶ οὗ ἀκολούθως ἐροῦμεν.