The term subject is taken in two ways: as subject of existence and as subject of predication. We have a subject of existence in such a case as that of substance, which is the subject of accidents, since these have existence in the substance, which is the subject of accidents, since these have existence in the substance but outside of it do not subsist. On the other hand, the subject of predication is the particular, for with predication the particular is subject to the more general, since the more general is predicated of the more particular—as the animal is predicated of man. Now, that which is universal is affirmed of a subject whereas that which is more particular is a subject of predication. And the accident is said to be in the substance as in a subject, whereas the substance is said to be a subject of existence.

[10b] Τὸ ὑποκείμενον δισσῶς λέγεται, τὸ μὲν πρὸς ὕπαρξιν, τὸ δὲ πρὸς κατηγορίαν. Καὶ πρὸς ὕπαρξιν μέν, ὥσπερ ὑπόκειται ἡ οὐσία τοῖς συμβεβηκόσιν: ἐν αὐτῇ γὰρ ἔχουσι τὸ εἶναι καὶ ἐκτὸς αὐτῆς οὐχ ὑφίστανται. Τὸ δὲ πρὸς κατηγορίαν ὑποκείμενόν ἐστι τὸ μερικόν: ὑπόκειται γὰρ τὸ μερικὸν τῷ καθολικωτέρῳ πρὸς κατηγορίαν, ἐπειδὴ τὸ καθολικώτερον κατηγορεῖται τοῦ μερικωτέρου, ὡς τὸ ζῷον κατηγορεῖται τοῦ ἀνθρώπου. Λέγεται δὲ τὸ μὲν καθόλου καθ' ὑποκειμένου, τὸ δὲ μερικώτερον ὑποκείμενον πρὸς κατηγορίαν. Λέγεται δὲ τὸ συμβεβηκὸς ἐν ὑποκειμένῳ τῇ οὐσίᾳ, ἡ δὲ οὐσία ὑποκείμενον πρὸς ὕπαρξιν.