τὸν κάμηλον οὐχ ὁρᾷς ὅτι ἀκάθαρτον εἶναί φησι ζῷον ὁ νόμος, ἐπειδὴ μηρυκᾶται μέν, οὐ διχηλεῖ δέ (Lev. 11, 4); καίτοι γε πρὸς τὴν ῥητὴν ἐπίσκεψιν οὐκ οἶδ’ ὃν ἔχει λόγον ἡ προσαποδοθεῖσα αἰτία, πρὸς δὲ τὴν δι’ ὑπονοιῶν ἀναγκαιότατον· ὥσπερ γὰρ τὸ μηρυκώμενον τὴν προκαταβληθεῖσαν ὑπαναπλέουσαν αὖθις ἐπιλεαίνει τροφήν, οὕτως ἡ ψυχὴ τοῦ φιλομαθοῦς, ἐπειδάν τινα δι’ ἀκοῆς δέξηται θεωρήματα, λήθῃ μὲν αὐτὰ οὐ παραδίδωσιν, ἠρεμήσασα δὲ καθ’ ἑαυτὴν ἕκαστα μεθ’ ἡσυχίας τῆς πάσης ἀναπολεῖ καὶ εἰς ἀνάμνησιν τῶν πάντων ἔρχεται. μνήμη δ’ οὐ πᾶσα ἀγαθόν, ἀλλ’ ἡ ἐπὶ μόνοις τοῖς ἀγαθοῖς, ἐπεὶ τό γε ἄληστα εἶναι τὰ κακὰ βλαβερώτατον· οὗ ἕνεκα πρὸς τελειότητα χρεία τοῦ διχηλεῖν, ἵνα τοῦ μνημονικοῦ δίχα τμηθέντος ὁ λόγος διὰ στόματος, οὗ πέρατα ἡ φύσις διττὰ εἰργάσατο χείλη, ῥέων διαστείλῃ τό τε ὠφέλιμον καὶ τὸ ἐπιζήμιον μνήμης γένους εἶδος.
(Philo, Peri Geōrgias 131-133)
Do you not see that the Law says that the camel is an unclean animal, because, though it chews the cud, it does not part the hoof (Lev. xi. 4)? And yet, if we fix our eyes on the literal way of regarding the matter, I do not know what principle there is in the reason given for the camel’s uncleanness; but if we look to the way suggested by latent meanings there is a most vital principle. For as the animal that chews the cud renders digestible the food taken in before as it rises again to the surface, so the soul of the keen learner, when it has by listening taken in this and that proposition, does not hand them over to forgetfulness, but in stillness all alone goes over them one by one quite quietly, and so succeeds in recalling them all to memory. Not all memory, however, is a good thing, but that which is brought to bear upon good things only, for it would be a thing most noxious that evil should be unforgettable. That is why, if perfection is to be attained, it is necessary to divide the hoof, in order that, the faculty of memory being cut in twain, language as it flows through the mouth, for which Nature wrought lips as twin boundaries, may separate the beneficial and the injurious forms of memory. (tr. Francis Henry Colson & George Herbert Whitaker)