I. Περὶ τῆς οὐσίας ἡ θεωρία· τῶν γὰρ οὐσιῶν αἱ ἀρχαὶ καὶ τὰ αἴτια ζητοῦνται. καὶ γὰρ εἰ ὡς 20 ὅλον τι τὸ πᾶν, ἡ οὐσία πρῶτον μέρος· καὶ εἰ τῷ ἐφεξῆς, κἂν οὕτω πρῶτον ἡ οὐσία, εἶτα τὸ ποιόν, εἶτα τὸ ποσόν. ἅμα δ᾿ οὐδ᾿ ὄντα ὡς εἰπεῖν ἁπλῶς ταῦτα,1 ἀλλὰ ποιότητες καὶ κινήσεις, ἢ2 καὶ τὸ οὐ λευκὸν καὶ τὸ οὐκ εὐθύ· λέγομεν γοῦν εἶναι καὶ ταῦτα, οἷον “ἔστιν οὐ λευκόν.” ἔτι οὐδὲν τῶν 25 ἄλλων χωριστόν. μαρτυροῦσι δὲ καὶ οἱ ἀρχαῖοι ἔργῳ· τῆς γὰρ οὐσίας ἐζήτουν ἀρχὰς καὶ στοιχεῖα καὶ αἴτια. οἱ μὲν οὖν νῦν τὰ καθόλου οὐσίας μᾶλλον τιθέασιν· τὰ γὰρ γένη καθόλου, ἅ φασιν ἀρχὰς καὶ οὐσίας εἶναι μᾶλλον διὰ τὸ λογικῶς ζητεῖν· οἱ δὲ πάλαι τὰ καθ᾿ ἕκαστα,3 οἷον πῦρ καὶ 30 γῆν, ἀλλ᾿ οὐ τὸ κοινὸν σῶμα. Οὐσίαι δὲ τρεῖς, μία μὲν αἰσθητή—ἧς ἡ μὲν ἀΐδιος ἡ δὲ φθαρτή, ἣν πάντες ὁμολογοῦσιν, οἷον τὰ φυτὰ καὶ τὰ ζῷα [ἡ δ᾿ ἀΐδιος]4—ἧς ἀνάγκη τὰ στοιχεῖα λαβεῖν, εἴτε ἓν εἴτε πολλά· ἄλλη δὲ ἀκίνητος, καὶ ταύτην φασί τινες
I. Our inquiry is concerned with substance; for Book xii. Substance, and especially nonsensible substance. it is the principles and causes of substances that we are investigating. Indeed if the universe is to be regarded as a whole, substance is its first part; and if it is to be regarded as a succession,a even so substance Substance is the primary reality. is first, then quality, then quantity. Moreover, the latter hardly exist at all in the full sense, but are merely qualifications and affections of Being. Otherwise “not-white” and “not-straight” would also exist; at any rate we say that they too “are,” e.g., “it is not white.” Further, none of the other2 categories is separately existent. Even the ancients in effect testify to this, for it was of substance that they sought the principles and elements and causes. Present-day thinkersb tend to regard universals as substance, because genera are universal, and they hold that these are more truly principles and substances because they approach the question theoretically; but the ancients identified substance with particular things, e.g. fire and earth, and not with body in general.
Now there are three kinds of substance. One is3 sensible (and may be either eternalc or perishable; substance may be (a) sensible and eternal the latter, e.g. plants and animals, is universally recognized); of this we must apprehend the elements, whether they are one or many. Another is4