Aristotle, Nicomachean Ethics, Book 5 40:

τὸ γὰρ ἀνάλογον οὐ μόνον ἐστὶ μοναδικοῦ ἀριθμοῦ ἴδιον, ἀλλ’ ὅλωσ ἀριθμοῦ· ἡ γὰρ ἀναλογία ἰσότησ ἐστὶ λόγων, καὶ ἐν τέτταρσιν ἐλαχίστοισ. ἡ μὲν οὖν διῃρημένη ὅτι ἐν τέτταρσι, δῆλον. ἀλλὰ καὶ ἡ συνεχήσ· τῷ γὰρ ἑνὶ ὡσ δυσὶ χρῆται καὶ δὶσ λέγει, οἱο͂ν ὡσ ἡ τοῦ α πρὸσ τὴν τοῦ β, οὕτωσ ἡ τοῦ β πρὸσ τὴν τοῦ γ. δὶσ οὖν ἡ τοῦ β εἴρηται·