Plato, Meno 79b

ἐστιν οἷόν τʼ εἶναι τἀγαθὰ πορίζεσθαι μετὰ δικαιοσύνης· τοῦτο δὲ φῂς μόριον ἀρετῆς εἶναι; ἔγωγε. οὐκοῦν συμβαίνει ἐξ ὧν σὺ ὁμολογεῖς, τὸ μετὰ μορίου ἀρετῆς πράττειν ὅτι ἂν πράττῃ, τοῦτο ἀρετὴν εἶναι· τὴν γὰρ δικαιοσύνην μόριον φῂς ἀρετῆς εἶναι, καὶ ἕκαστα τούτων. τί οὖν δὴ τοῦτο λέγω; ὅτι ἐμοῦ δεηθέντος ὅλον εἰπεῖν τὴν ἀρετήν, αὐτὴν μὲν πολλοῦ δεῖς εἰπεῖν ὅτι ἐστίν, πᾶσαν δὲ φῂς πρᾶξιν ἀρετὴν εἶναι, ἐάνπερ μετὰ μορίου

the ability to procure good things with justice; and this, you tell me, is a part of virtue? I do. Then it follows from your own admission that doing whatever one does with a part of virtue is itself virtue; for you say that justice is a part of virtue, and so is each of such qualities. You ask the meaning of my remark. It is that after my requesting you to speak of virtue as a whole, you say not a word as to what it is in itself, but tell me that every action is virtue provided that it is done