And right appears left and left right, because the visual rays come into contact with the rays emitted by the object in a manner contrary to the usual mode of meeting; but the right appears right, and the left left, when the position of one of the two concurring lights is reversed; and this happens when the mirror is concave and its smooth surface repels the right stream of vision to the left side, and the left to the right. Or if the mirror be turned vertically, then the concavity makes the countenance appear to be all upside down, and the lower rays are driven upwards and the upper downwards.

All these are to be reckoned among the second and co-operative causes which God, carrying into execution the idea of the best as far as possible, uses as his ministers. They are thought by most men not to be the second, but the prime causes of all things, because they freeze and heat, and contract and dilate, and the like. But they are not so, for they are incapable of reason or intellect; the only being which can properly have mind is the invisible soul, whereas fire and water, and earth and air, are all of them visible bodies. The lover of intellect and knowledge ought to explore causes of intelligent nature first of all, and, secondly, of those things which, being moved by others, are compelled to move others. And this is what we too must do. Both kinds of causes should be acknowledged by us, but a distinction should be made between those which are endowed with mind and are the workers of things fair and good, and those which are deprived of intelligence and always produce chance effects without order or design. Of the second or co-operative causes of sight, which help to give to the eyes the power which they now possess, enough has been said. I will therefore now proceed to speak of the higher use and purpose for which God has given them to us. 

δεξιὰ δὲ φαντάζεται τὰ ἀριστερά͵ ὅτι τοῖς ἐναντίοις μέρεσιν τῆς ὄψεως περὶ τἀναντία μέρη γίγνεται ἐπαφὴ παρὰ τὸ καθεστὸς ἔθος τῆς προσβολῆς· δεξιὰ δὲ τὰ δεξιὰ καὶ τὰ ἀριστερὰ ἀριστερὰ τοὐναντίον͵ ὅταν μεταπέσῃ συμπηγνύμενον ᾧ συμπήγνυται φῶς͵ [46c] τοῦτο δέ͵ ὅταν ἡ τῶν κατόπτρων λειότης͵ ἔνθεν καὶ ἔνθεν ὕψη λαβοῦσα͵ τὸ δεξιὸν εἰς τὸ ἀριστερὸν μέρος ἀπώσῃ τῆς ὄψεως καὶ θάτερον ἐπὶ θάτερον. κατὰ δὲ τὸ μῆκος στραφὲν τοῦ προσώπου ταὐτὸν τοῦτο ὕπτιον ἐποίησεν πᾶν φαίνεσθαι͵ τὸ κάτω πρὸς τὸ ἄνω τῆς αὐγῆς τό τ΄ ἄνω πρὸς τὸ κάτω πάλιν ἀπῶσαν.

Ταῦτ΄ οὖν πάντα ἔστιν τῶν συναιτίων οἷς θεὸς ὑπηρετοῦσιν χρῆται τὴν τοῦ ἀρίστου κατὰ τὸ δυνατὸν ἰδέαν ἀποτελῶν· [46d] δοξάζεται δὲ ὑπὸ τῶν πλείστων οὐ συναίτια ἀλλὰ αἴτια εἶναι τῶν πάντων͵ ψύχοντα καὶ θερμαίνοντα πηγνύντα τε καὶ διαχέοντα καὶ ὅσα τοιαῦτα ἀπεργαζόμενα. λόγον δὲ οὐδένα οὐδὲ νοῦν εἰς οὐδὲν δυνατὰ ἔχειν ἐστίν. τῶν γὰρ ὄντων ᾧ νοῦν μόνῳ κτᾶσθαι προσήκει͵ λεκτέον ψυχήν - τοῦτο δὲ ἀόρατον͵ πῦρ δὲ καὶ ὕδωρ καὶ γῆ καὶ ἀὴρ σώματα πάντα ὁρατὰ γέγονεν - τὸν δὲ νοῦ καὶ ἐπιστήμης ἐραστὴν ἀνάγκη τὰς τῆς ἔμφρονος φύσεως αἰτίας πρώτας μεταδιώκειν͵ [46e] ὅσαι δὲ ὑπ΄ ἄλλων μὲν κινουμένων͵ ἕτερα δὲ κατὰ ἀνάγκης κινούντων γίγνονται͵ δευτέρας. ποιητέον δὴ κατὰ ταῦτα καὶ ἡμῖν· λεκτέα μὲν ἀμφότερα τὰ τῶν αἰτιῶν γένη͵ χωρὶς δὲ ὅσαι μετὰ νοῦ καλῶν καὶ ἀγαθῶν δημιουργοὶ καὶ ὅσαι μονωθεῖσαι φρονήσεως τὸ τυχὸν ἄτακτον ἑκάστοτε ἐξεργάζονται. τὰ μὲν οὖν τῶν ὀμμάτων συμμεταίτια πρὸς τὸ σχεῖν τὴν δύναμιν ἣν νῦν εἴληχεν εἰρήσθω· τὸ δὲ μέγιστον αὐτῶν εἰς ὠφελίαν ἔργον͵ δι΄ ὃ θεὸς αὔθ΄ ἡμῖν δεδώρηται͵ μετὰ τοῦτο ῥητέον.