οἷς δὲ πρόσεισι καὶ ἄπεισιν ἀριθμοῖς καὶ πλήθεσιν, ταῦτα μὴ διαμένειν, ἀλλ’ ἕτερα γίγνεσθαι ταῖς εἰρημέναις προσόδοις, ἐξαλλαγὴν τῆς οὐσίας λαμβανούσης. That it should be said of this perpetually changing material μήτ’ αὐξόμενον μήτε μειούμενον may appear strange; but the meaning is this: it can only be said of an individual thing that it increases and diminishes in so far as it remains one and the same subject, an ἰδίως ποιὸν during the change; but the material itself, which is ever changing, cannot be regarded as the one identical subject of increase and diminution. This idea is expanded by Alex. Aphro. Quæst. Nat. I. 5. [187] ποιὸν or ποιότης, and also ποιὸς (sc. λόγος). According to Simpl. 55. α, many Stoics assign a threefold meaning to ποιόν. The first, which is also the most extensive meaning, includes every kind of quality, whether essential or accidental—the πὼς ἔχον as well as the ποιόν. In the second meaning ποιὸν is used to express permanent qualities, including those which are derivative and non-essential—the σχέσεις. In the third and narrowest sense it expresses τοὺς ἀπαρτίζοντας (κατὰ τὴν ἐκφορὰν) καὶ ἐμμόνως ὄντας κατὰ διαφορὰν ποιοὺς, i.e. those qualities which faithfully represent essential attributes in their distinctive features. The substantive ποιότης is only used in the last sense. [188] Simpl. 57, ε (the passage is fully discussed by Petersen, 85, and Trendelenburg, 223): οἱ δὲ Στωϊκοὶ τὸ κοινὸν τῆς ποιότητος τὸ ἐπὶ τῶν σωμάτων λέγουσι διαφορὰν εἶναι οὐσίας οὐκ ἀποδιαληπτὴν (separable, i.e., from matter) καθ’ ἑαυτὴν, ἀλλ’ εἰς ἓν νόημα καὶ ἰδιότητα [sc. μίαν] ἀπολήγουσαν οὔτε χρόνῳ οὔτε ἰσχύϊ εἰδοποιουμένην, ἀλλὰ τῇ ἐξ αὐτῆς τοιουτότητι, καθ’ ἢν ποιοῦ ὑφίσταται γένεσις. In place of ἓν νόημα Petersen, 85, with the approval of Trendelenburg and Prantl (438, 96), reads ἐννόημα. To me, Brandis Schol. 69, a, 32, appears to retain it with reason, the meaning being that ποιότης constitutes no independent unity, but only a unity of conception. Non-essential qualities are by the Stoics excluded from the category of ποιὸν, and reckoned under that of πὼς ἔχον. The same distinction between what is essential and what is not essential is indicated in the terms ἕξις and σχέσις· ποιότητες, or essential properties, being called essential forms (ἕξεις or ἑκτά); non-essential qualities being called features or varieties (σχέσεις). See Simpl. 54, γ; 55, ε. In determining essential attributes, these, according to Simpl. 61, β (Schol. in Arist. 70, b, 43), are essential, not when they happen to be permanent, but when they spring from the nature of the object to which they belong: τὰς μὲν γὰρ σχέσεις ταῖς ἐπικτήτοις καταστάσεσι χαρακτηρίζεσθαι τὰς δὲ ἕξεις ταῖς ἐξ ἑαυτῶν ἐνεργείαις. A more limited meaning, that of local position, is given to σχέσις in Stob. Ecl. i. 410.