Plutarch, De Iside et Osiride 3

ἔτι πολλοὶ μὲν Ἑρμοῦ, πολλοὶ δὲ Προμηθέως ἱστορήκασιν αὐτὴν θυγατέρα· ὧν τὸν μὲν ἕτερον σοφίας καὶ προνοίας, Ἑρμῆν δὲ γραμματικῆς καὶ μουσικῆς εὑρετὴν νομίζοντες. διὸ καὶ τῶν ἐν Ἑρμοῦ πόλει Μουσῶν τὴν προτέραν Ἶσιν ἅμα καὶ Δικαιοσύνην καλοῦσι, σοφὴν οὖσαν, ὥσπερ εἴρηται, καὶ δεικνύουσαν τὰ θεῖα τοῖς ἀληθῶς καὶ δικαίως ἱεραφόροις καὶ ἱεροστόλοις προσαγορευομένοις. οὗτοι δʼ εἰσὶν οἱ τὸν ἱερὸν λόγον περὶ θεῶν πάσης καθαρεύοντα δεισιδαιμονίας καὶ περιεργίας ἐν τῇ ψυχῇ φέροντες ὥσπερ ἐν κίστῃ καὶ περιστέλλοντες, τὰ μὲν μέλανα καὶ σκιώδη τὰ δὲ φανερὰ καὶ λαμπρὰ τῆς περὶ θεῶν ὑποδηλοῦντα οἰήσεως, οἷα καὶ περὶ τὴν ἐσθῆτα τὴν ἱερὰν ἀποφαίνεται. διὸ καὶ τὸ κοσμεῖσθαι τούτοις τοὺς ἀποθανόντας Ἰσιακοὺς σύμβολόν ἐστι τοῦτον τὸν λόγον εἶναι μετʼ αὐτῶν, καὶ τοῦτον ἔχοντας ἄλλο δὲ μηδὲν ἐκεῖ βαδίζειν. οὔτε γὰρ φιλοσόφους πωγωνοτροφίαι, ὦ Κλέα, καὶ τριβωνοφορίαι ποιοῦσιν, οὔτʼ Ἰσιακοὺς αἱ λινοστολίαι καὶ ξυρήσεις· ἀλλʼ Ἰσιακός ἐστιν ὡς ἀληθῶς ὁ τὰ δεικνύμενα καὶ δρώμενα περὶ τοὺς θεοὺς τούτους, ὅταν νόμῳ παραλάβῃ, λόγῳ ζητῶν καὶ φιλοσοφῶν περὶ τῆς ἐν αὐτοῖς ἀληθείας.

Moreover, many writers have held her to be the daughter of Hermes, and many others the daughter of Prometheus, because of the belief that Prometheus is the discoverer of wisdom and forethought, and Hermes the inventor of grammar and music. For this reason they call the first of the Muses at Hermopolis Isis as well as Justice: for she is wise, as I have said, and discloses the divine mysteries to those who truly and justly have the name of bearers of the sacred vessels and wearers of the sacred robes. These are they who within their own soul, as though within a casket, bear the sacred writings about the gods clear of all superstition and pedantry; and they cloak them with secrecy, thus giving intimations, some dark and shadowy, some clear and bright, of their concepts about the gods, intimations of the same sort as are clearly evidenced in the wearing of the sacred garb. For this reason, too, the fact that the deceased votaries of Isis are decked with these garments is a sign that these sacred writings accompany them, and that they pass to the other world possessed of these and of naught else. It is a fact, Clea, that having a beard and wearing a coarse cloak does not make philosophers, nor does dressing in linen and shaving the hair make votaries of Isis; but the true votary of Isis is he who, when he has legitimately received what is set forth in the ceremonies connected with these gods, uses reason in investigating and in studying the truth contained therein.