LCL 234: 102-103
45 κατὰ τὴν τῶν ὀμμάτων εὐθυωρίαν, ὅπῃπερ ἂν ἀντερείδῃ τὸ προσπῖπτον ἔνδοθεν πρὸς ὃ τῶν ἔξω ξυνέπεσεν. ὁμοιοπαθὲς δὴ δι᾿ ὁμοιότητα πᾶν Dγενόμενον, ὅτου τε ἂν αὐτό ποτε ἐφάπτηται καὶ ὃ ἂν ἄλλο ἐκείνου, τούτων τὰς κινήσεις διαδιδὸν εἰς ἅπαν τὸ σῶμα μέχρι τῆς ψυχῆς αἴσθησιν παρέσχετο ταύτην, ᾗ δὴ ὁρᾷν φαμέν. ἀπελθόντος δὲ εἰς νύκτα τοῦ ξυγγενοῦς πυρὸς ἀποτέτμηται· πρὸς γὰρ ἀνόμοιον ἐξιὸν ἀλλοιοῦταί τε αὐτὸ καὶ κατασβέννυται, ξυμφυὲς οὐκέτι τῷ πλησίον ἀέρι γιγνόμενον, ἅτε πῦρ οὐκ ἔχοντι. παύεταί τε οὖν ὁρῶν, ἔτι τε ἐπαγωγὸν ὕπνου γίγνεται· σωτηρίαν γὰρ Eἣν οἱ θεοὶ τῆς ὄψεως ἐμηχανήσαντο, τὴν τῶν βλεφάρων φύσιν, ὅταν ταῦτα ξυμμύσῃ, καθείργνυσι τὴν τοῦ πυρὸς ἐντὸς δύναμιν, ἡ δὲ διαχεῖ τε καὶ ὁμαλύνει τὰς ἐντὸς κινήσεις, ὁμαλυνθεισῶν δὲ ἡσυχία γίγνεται, γενομένης δὲ πολλῆς μὲν ἡσυχίας βραχυόνειρος ὕπνος ἐμπίπτει, καταλειφθεισῶν δέ τινων κινήσεων μειζόνων, οἷαι καὶ ἐν οἵοις ἂν 46τόποις λείπωνται, τοιαῦτα καὶ τοσαῦτα παρέσχοντο ἀφομοιωθέντα ἐντός, ἔξω τε ἐγερθεῖσιν ἀπομνημονευόμενα, φαντάσματα.
Τὸ δὲ περὶ τὴν τῶν κατόπτρων εἰδωλοποιίαν, καὶ πάντα ὅσα ἐμφανῆ καὶ λεῖα, κατιδεῖν οὐδὲν ἔτι χαλεπόν· ἐκ γὰρ τῆς ἐντὸς ἐκτός τε τοῦ πυρὸς ἑκατέρου κοινωνίας ἀλλήλοις, ἑνός τε αὖ περὶ τὴν λειότητα ἑκάστοτε γενομένου καὶ πολλαχῇ μεταρρυθμισθέντος, Bπάντα τὰ τοιαῦτα ἐξ ἀνάγκης ἐμφαίνεται, τοῦ περὶ τὸ πρόσωπον πυρὸς τῷ περὶ τὴν
kindred substance along the path of the eyes’ vision, wheresoever the fire which streams from within collides with an obstructing object without. And this substance, having all become similar in its properties because of its similar nature, distributes the motions of every object it touches, or whereby it is touched, throughout all the body even unto the Soul, and brings about that sensation which we now term “seeing.” But when the kindred fire vanishes into night, the inner fire is cut off; for when it issues forth into what is dissimilar it becomes altered in itself and is quenched, seeing that it is no longer of like nature with the adjoining air, since that air is devoid of fire. Wherefore it leaves off seeing, and becomes also an inducement to sleep. For the eyelids—whose structure the Gods devised as a safeguard for the vision,—when they are shut close, curb the power of the inner fire; which power dissipates and allays the inward motions, and upon their allaying quiet ensues; and when this quiet has become intense there falls upon us a sleep that is well-nigh dreamless; but when some greater motions are still left behind, according to their nature and the positions they occupy such and so great are the images they produce, which images are copied within and are remembered by the sleepers when they awake out of the dream.
And it is no longer difficult to perceive the truth about the formation of images in mirrors and in bright and smooth surfaces of every kind. It is from the combination with each other of the inner and the outer fires, every time that they unite on the smooth surface and are variously deflected, that all such reflections necessarily result, owing to the fire of the reflected face coalescing with the fire of the vision