λεχθέντων δὲ τούτων κἀμοῦ τῷ Λευκίῳ τὸν λόγον παραδιδόντος, ἐπὶ τὰς ἀποδείξεις βαδίζοντος τοῦ δόγματος, Ἀριστοτέλης μειδιάσας μαρτύρομαι εἶπεν ὅτι τὴν πᾶσαν ἀντιλογίαν πεποίησαι πρὸς τοὺς αὐτὴν ὴν μὲν, ἡμίπυρον εἶναι τὴν σελήνην ὑποτιθεμένους, κοινῇ δὲ τῶν σωμάτων τὰ μὲν ἄνω τὰ δὲ κάτω ῥέπειν ἐξ ἑαυτῶν φάσκοντας· εἰ δʼ ἔστι τις ὁ λέγων, κύκλῳ τε κινεῖσθαι κατὰ φύσιν τὰ ἄστρα καὶ πολὺ παρηλλαγμένης οὐσίας εἶναι τῶν τεττάρων, οὐδʼ ἀπὸ τύχης ἦλθεν ἐπὶ μνήμην ἡμῖν, ὥστʼ ἐμέ τε πραγμάτων ἀπηλλάχθαι καὶ σέ, ὦ Λεύκιε καὶ ὁ Λεύκιος ἣκιστα, ὠγαθέ εἶπεν ἀλλὰ τἄλλα, μὲν ἴσως ἄστρα καὶ τὸν ὅλον οὐρανὸν εἴς τινα φύσιν καθαρὰν καὶ εἰλικρινῆ καὶ τῆς κατὰ πάθος ἀπηλλαγμένην μεταβολῆς τιθεμένοις ὑμῖν καὶ κύκλον ἄγουσιν ἀιδίου καὶ ἀτελευτήτου περιφορᾶς […] οὐκ ἄν τις ἔν γε τῷ νῦν διαμάχοιτο, καίτοι μυρίων οὐσῶν ἀποριῶν. ὅταν δὲ καταβαίνων ὁ λόγος οὕτω θίγῃ τῆς σελήνης, οὐκέτι φυλάττει τὴν ἀπάθειαν ἐν αὐτῇ καὶ τὸ κάλλος ἐκεῖνο τοῦ σώματος ἀλλʼ ἵνα τὰς ἄλλας ἀνωμαλίας καὶ διαφορὰς ἀφῶμεν, αὐτὸ τοῦτο τὸ διαφαινόμενον πρόσωπον πάθει τινὶ τῆς οὐσίας ἢ ἀναμίξει πως ἑτέρας ἐπιγέγονε· πάσχει δέ τι καὶ τὸ μιγνύμενον· ἀποβάλλει γὰρ τὸ εἰλικρινές, βίᾳ τοῦ χείρονος ἀναπιμπλάμενον. αὐτῆς δὲ νώθειαν καὶ τάχους ἀμβλύτητα καὶ τὸ θερμὸν ἀδρανὲς καὶ ἀμαυρόν, ᾧ κατὰ τὸν Ἴωνα μέλας οὐ πεπαίνεται βότρυς, εἰς τί θησόμεθα πλὴν ἀσθένειαν αὐτῆς καὶ πάθος, εἰ πάθους ἀιδίῳ σώματι καὶ ὀλυμπίῳ μέτεστιν; ὅλως γάρ, ὦ φίλε Ἀριστότελες, γῆ μὲν οὖσα πάγκαλόν τι χρῆμα καὶ σεμνὸν ἀναφαίνεται καὶ κεκοσμημένον· ὡς δʼ ἄστρον ἢ φῶς ἤ τι σῶμα θεῖον καὶ οὐράνιον, δέδια μὴ ἄμορφος καὶ ἀπρεπὴς καὶ καταισχύνουσα τὴν καλὴν ἐπωνυμίαν εἴ γε τῶν ἐν οὐρανῷ τοσούτων τὸ πλῆθος ὄντων μόνη φωτὸς ἀλλοτρίου δεομένη περίεισι κατὰ Παρμενίδην αἰεὶ παπταίνουσα πρὸς αὐγὰς ἠελίοιο ὁ μὲν οὖν ἑταῖρος ἐν, τῇ διατριβῇ τοῦτο δὴ τὸ Ἀναξαγόρειον ἀποδεικνὺς ὡς ἥλιος ἐντίθησι τῇ σελήνῃ τὸ λαμπρόν εὐδοκίμησεν· ἐγὼ δὲ ταῦτα μὲν οὐκ ἐρῶ, ἃ παρʼ ὑμῶν· ἢ μεθʼ ὑμῶν ἔμαθον, ἑκὼν δὲ πρὸς τὰ λοιπὰ βαδιοῦμαι. φωτίζεσθαι τοίνυν τὴν σελήνην οὐχ ὡς ὕελον ἢ κρύσταλλον ἐλλάμψει καὶ διαφαύσει τοῦ ἡλίου πιθανόν ἐστιν· οὐδʼ αὖ κατὰ σύλλαμψίν τινα καὶ συναυγασμόν, ὥσπερ αἱ δᾷδες αὐξομένου τοῦ φωτός· οὕτω γὰρ οὐδὲν ἧττον ἐν νουμηνίαις ἢ διχομηνίαις ἔσται πανσέληνος· ἡμῖν, εἰ μὴ στέγει μηδʼ ἀντιφράττει τὸν ἥλιον ἀλλὰ διίησιν ὑπὸ μανότητος ἢ κατὰ σύγκρασιν εἰσλάμπει; καὶ συνεξάπτει περὶ αὐτὴν τὸ φῶς. οὐ γὰρ ἔστιν ἐκκλίσεις οὐδʼ ἀποστροφὰς αὐτῆς, ὥσπερ ὅταν ᾖ διχότομος καὶ ἀμφίκυρτος ἢ μηνοειδής, αἰτιᾶσθαι περὶ τὴν σύνοδον ἀλλὰ κατὰ στάθμην, φησὶ Δημόκριτος, ἱσταμένη τοῦ φωτίζοντος ὑπολαμβάνει καὶ δέχεται τὸν ἥλιον· ὥστʼ αὐτήν τε φαίνεσθαι καὶ διαφαίνειν ἐκεῖνον εἰκὸς ἦν. ἡ δὲ πολλοῦ δεῖ τοῦτο ποιεῖν· αὐτή τε γὰρ ἄδηλός ἐστι τηνικαῦτα κἀκεῖνον ἀπέκρυψε καὶ ἠφάνισε πολλάκις ἀπεσκέδασεν δὲ οἱ αὐγάς ὥσπερ φησιν Ἐμπεδοκλῆς ἐς γαῖαν καθύπερθεν, ἀπεσκνίφωσε δὲ γαίης / τόσσον, ὅσον τʼ εὖρος γλαυκώπιδος ἔπλετο μήνης, / καθάπερ εἰς νύκτα καὶ σκότος οὐκ εἰς ἄστρον ἑτερο τοῦ φωτὸς ἐμπεσόντος. ὃ δὲ λέγει Ποσειδώνιος, ὡς ὑπὸ βάθους τῆς σελήνης οὐ περαιοῦται διʼ αὐτῆς τὸ τοῦ ἡλίου φῶς πρὸς ἡμᾶς, ἐλέγχεται καταφανῶς. ὁ γὰρ ἀὴρ ἄπλετος ὢν καὶ βάθος ἔχων πολλαπλάσιον τῆς σελήνης ὅλος ἐξηλιοῦται καὶ καταλάμπεται ταῖς αὐγαῖς. ἀπολείπεται τοίνυν τὸ τοῦ Ἐμπεδοκλέους, ἀνακλάσει τινὶ τοῦ ἡλίου πρὸς τὴν σελήνην γίγνεσθαι τὸν ἐνταῦθα φωτισμὸν ἀπʼ αὐτῆς;. ὅθεν οὐδὲ θερμὸν οὐδὲ λαμπρὸν ἀφικνεῖται πρὸς ἡμᾶς, ὥσπερ ἦν εἰκός, ἐξάψεως καὶ μίξεως […] φώτων γεγενημένης. ἀλλʼ οἷον αἵ τε φωναὶ κατὰ τὰς ἀνακλάσεις ἀμαυροτέραν ἀναφαίνουσι τὴν τοῦ φθέγματος αἵ τε πληγαὶ τῶν ἀφαλλομένων βελῶν μαλακώτεραι προσπίπτουσιν· ὣς αὐγὴ τύψασα σεληναίης κύκλον εὐρύν ἀσθενῆ καὶ ἀμυδρὰν ἀνάρροιαν ἴσχει πρὸς ἡμᾶς, διὰ τὴν κλάσιν ἐκλυομένης τῆς δυνάμεως.
These things being said, as I was giving Lucius his turn to follow and continue the discourse,—there being nothing left to be added but the demonstrations of this doctrine,—Aristotle smiling said: I am a witness, that you have directed all your contradictions and all your refutations against those who, supposing the moon to be half fire, affirm in general that all bodies do of their own accord tend either upwards or downwards; but if there is any one who holds that the stars have of their own nature a circular motion, and that they are of a substance wholly different from the four elements, you have not thought of saying any thing, so much as accidentally or by the way, against him; and therefore I am wholly unconcerned in your discourse.
Indeed, good sir, said Lucius, if you should suppose the other stars, and the whole heaven apart, to be of a pure and sincere nature, free from all change and alteration of passion, and should bring in also a circle, in which they make their motion by a perpetual revolution, you would not perhaps find any one now to contradict you, though there are in this infinite doubts and difficulties. But when the discourse descends so far as to touch the moon, it cannot maintain in her that perfection of being exempt from all passion and alteration, nor that heavenly beauty of her body. But to let pass all other inequalities and differences, the very face which appears in the body of the moon necessarily proceeds from some passion of her own substance or the mixture of another; for what is mixed suffers, because it loses its first purity, being filled by force with that which is worse. Besides, as for the slowness and dulness of her course, her feeble and inefficacious heat, by which, as Ion says, The black grape comes not to maturity, / to what shall we attribute them but to her weakness and passion, if an eternal and celestial body can be subject to passion?
In brief, my friend Aristotle, if the moon is earth, she is a most fair and admirable thing, and excellently well adorned; but if you regard her as a star or light or a certain divine and heavenly body, I am afraid she will prove deformed and foul, and disgrace that beautiful appellation, if of all bodies, which are in heaven so numerous, she alone stands in need of light borrowed of another, and, as Parmenides has it, Looks always backwards on the sun’s bright rays. /
Our friend therefore indeed, having in a lecture of his demonstrated this proposition of Anaxagoras, that the sun communicates to the moon what brightness she has, was well esteemed for it. As for me, I will not say what I have learned of you or with you, but having taken it for granted, will pass on to the rest. It is then probable that the moon is illuminated, not like a glass or crystal, by the brightness of the sun’s rays shining through her, nor yet again, by a certain collustration and conjunction of light and brightness, as when many torches set together augment the light of one another. For so she would be no less full in her conjunction or first quarter than in her opposition, if she did not obstruct or repel the rays of the sun, but let them pass through her by reason of her rarity, or if he did by a contemperature shine upon her and kindle the light within her. For we cannot allege her declinations and aversions in the conjunction or new moon, as when it is half-moon or when she appears crescent or in the wane; but being then perpendicularly (as Democritus says) under him that illuminates her, she receives and admits the sun; so that then it is probable she should appear, and he shine through her. But this she is so far from doing, that she is not only then unseen, but also often hides the sun, as Empedocles has it: The sun’s bright beams from us she turns aside, / And of the earth itself as much doth hide, / As her orb’s breadth can cover; / as if the light of the sun fell not upon another star, but upon night and darkness. And as for what Posidonius says, that the depth of the moon’s body is the cause why the light of the sun cannot pierce through her to us, this is evidently refuted; for the air, which is infinite and of a far greater depth than the body of the moon, is nevertheless all over illustrated and enlightened by the rays of the sun.
It remains then that, according to the opinion of Empedocles, the light of the moon which appears to us comes from the repercussion and reflection of the sun’s beams. And for this reason it comes not to us hot and bright, as in all probability it would, if her shining proceeded either from inflammation or the commixtion of two lights. But as voices reverberated cause an echo more obscure and less express than the speech that was pronounced, and as the blows of darts and arrows, rebounding from some wall against which they are shot, are more mild and gentle; So Titan’s lustre, smiting the moon’s orb, / yields but a faint and feeble reflection and repercussion of brightness upon us, its force being abated and weakened by the refraction.
ὑπολαβὼν δʼ ὁ Σύλλας ἀμέλει ταῦτʼ εἶπεν ἔχει τινὰς πιθανότητας· ὃ, δʼ ἰσχυρότατόν ἐστι τῶν ἀντιπιπτόντων, πότερον ἔτυχέ τινος παραμυθίας ἢ παρῆλθεν ἡμῶν τὸν ἑταῖρον; τί τοῦτο λέγεις ἔφη ὁ Λεύκιος ἢ τὸ πρὸς τὴν διχότομον ἀπορούμενον; πάνυ μὲν οὖν ὁ Σύλλας εἶπεν· ἔχει γάρ τινα λόγον τό, πάσης ἐν ἴσαις γωνίαις γιγνομένης ἀνακλάσεως, ὅταν ἡ σελήνη διχότομος οὖσα μεσουρανῇ, μὴ φέρεσθαι τὸ φῶς ἐπὶ γῆς ἀπʼ αὐτῆς ἀλλʼ ὀλισθάνειν ἐπέκεινα τῆς γῆς· ὁ γὰρ ἥλιος ἐπὶ τοῦ ὁρίζοντος ὢν ἅπτεται τῇ ἀκτῖνι τῆς σελήνης· διὸ καὶ κλασθεῖσα πρὸς ἴσας ἐπὶ θάτερον ἐκπεσεῖται πέρας καὶ οὐκ ἀφήσει δεῦρο τὴν αὐγήν· ἢ διαστροφὴ μεγάλη καὶ παράλλαξις ἔσται τῆς γωνίας, ὅπερ ἀδύνατόν ἐστιν. ἀλλὰ νὴ Δίʼ εἶπεν ὁ Λεύκιος καὶ τοῦτʼ ἐρρήθη καὶ πρός γε Μενέλαον ἀποβλέψας ἐν τῷ διαλέγεσθαι τὸν μαθηματικὸν αἰσχύνομαι μέν ἔφη σοῦ παρόντος, ὦ φίλε Μενέλαε, θέσιν ἀναιρεῖν μαθηματικήν, ὥσπερ θεμέλιον τοῖς κατοπτρικοῖς ὑποκειμένην πράγμασιν· ἀνάγκη δʼ εἰπεῖν ὅτι τὸ πρὸς τὰς ἴσας γίγνεσθαι γωνίας ἀνάκλασιν πᾶσαν, οὔτε φαινόμενον αὐτόθεν οὔθʼ ὁμολογούμενόν ἐστιν· ἀλλὰ διαβάλλεται μὲν· ἐπὶ τῶν κυρτῶν κατόπτρων, ὅταν ἐμφάσεις ποιῇ μείζονας ἑαυτῶν πρὸς ἓν τὸ τῆς ὄψεως σημεῖον, διαβάλλεται δὲ τοῖς διπτύχοις κατόπτροις, ὧν ἐπικλιθέντων πρὸς ἄλληλα καὶ γωνίας ἐντὸς γενομένης, ἑκάτερον τῶν ἐπιπέδων. διττὴν ἔμφασιν ἀποδίδωσι καὶ ποιεῖ τέτταρας εἰκόνας ἀφʼ ἑνὸς προσώπου, δύο μὲν ἀντιστρόφους ἐν τοῖς ἔξωθεν, μέρεσι, δύο δὲ δεξιοφανεῖς ἀμαυρὰς ἐν βάθει τῶν κατόπτρων. ὧν τῆς γενέσεως τὴν αἰτίαν Πλάτων ἀποδίδωσιν. εἴρηκε γὰρ ὅτι, τοῦ κατόπτρου ἔνθεν καὶ ἔνθεν ὕψος λαβόντος, ὑπαλλάττουσιν αἱ ὄψεις τὴν ἀνάκλασιν ἀπὸ τῶν ἑτέρων ἐπὶ θάτερα μεταπίπτουσαν. εἴπερ οὖν τῶν ὄψεων αἱ μὲν εὐθὺς πρὸς ἡμᾶς […] ἀνατρέχουσιν, αἱ δʼ ἐπὶ θάτερα μέρη τῶν κατόπτρων ὀλισθάνουσαι πάλιν ἐκεῖθεν ἀναφέρονται πρὸς ἡμᾶς, οὐ δυνατὸν ἐστιν ἐν ἴσαις γωνίαις γίγνεσθαι πάσας ἀνακλάσεις, ὅσας ὁμόσε χωρ […] οῦντες ἀξιοῦσιν αὑτοῖς τοῖς ἀπὸ τῆς σελήνης. ἐπὶ γῆν φερομένοις ῥεύμασι τὴν ἰσότητα τῶν γωνιῶν ἀναιρεῖν, πολλῷ τοῦτʼ ἐκείνου πιθανώτερον εἶναι νομίζοντες. οὐ μὴν ἀλλʼ εἰ δεῖ τοῦτο χαρίζεσθαι τῇ πολλὰ δὴ. φίλῃ γεωμετρίᾳ καὶ δοῦναι, πρῶτον μὲν ἀπὸ τῶν ἠκριβωμένων ταῖς λειότησι συμπίπτειν ἐσόπτρων εἰκός ἐστιν· ἡ δὲ σελήνη πολλὰς ἀνωμαλίας ἔχει καὶ τραχύτητας, ὥστε τὰς αὐγὰς ἀπὸ σώματος μεγάλου προσφερομένας ὕψεσιν ἀξιολόγοις, ἀντιλάμψεις καὶ διαδόσεις ἀπʼ ἀλλήλων λαμβάνουσιν, ἀνακλᾶσθαί τε παντοδαπῶς καὶ περιπλέκεσθαι καὶ συνάπτειν αὐτὴν ἑαυτῇ τὴν, ἀνταύγειαν, οἷον ἀπὸ πολλῶν φερομένην πρὸς ἡμᾶς κατόπτρων. ἔπειτα κἂν πρὸς αὐτῇ τῇ σελήνῃ τὰς ἀντανακλάσεις ἐν ἴσαις γωνίαις ποιῶμεν, οὐκ ἀδύνατον φερομένας ἐν διαστήματι τοσούτῳ τὰς αὐγὰς κλάσεις ἴσχειν καὶ περιολισθήσεις, ὡς συγχεῖσθαι καὶ λάμπειν τὸ φῶς. ἔνιοι δὲ καὶ δεικνύουσι γράφοντες, ὅτι πολλὰ τῶν φώτων αὐγὴν ἀφίησι κατὰ γραμμὴν ὑπὸ τὴν κεκλιμένην ὑποταθεῖσαν· σκευωρεῖσθαι δʼ ἅμα λέγοντι, διάγραμμα, καὶ ταῦτα πρὸς πολλούς, οὐκ ἐνῆν.
Sylla then, taking up the discourse, said: There is indeed a great deal of probability in all that you have spoken. But as to the strongest objection that is brought against it, has it, think you, been any way weakened by this discourse? Or has our friend quite passed it over in silence?
What opposition do you mean, said Lucius? Is it the difficulty about the moon, when one half of her appears enlightened?
The very same, answered Sylla. For there is some reason, seeing that all reflection is made by equal angles, that when the half-moon is in the midst of heaven, the light proceeding from her should not be carried upon the earth, but glance and fall beyond and on one side of it. For the sun, being placed in the horizon, touches the moon with its beams; which, being equally reflected, will therefore necessarily fall on the other bound of the horizon, and not send their light down hither; or else there will be a great distortion and difference of the angle, which is impossible.
And yet, by Jupiter, replied Lucius, this has not been forgotten or overpassed, but already spoken to. And casting his eye, as he was discoursing, upon the mathematician Menelaus; I am ashamed, said he, in your presence, dear Menelaus, to attempt the subverting and overthrowing of a mathematical position, which is supposed as a basis and foundation to the doctrine of the catoptrics concerning the causes and reasons of mirrors. And yet of necessity I must. For it neither appears of itself nor is confessed as true, that all reflections are at equal angles; but this position is first checked and contradicted in concave mirrors, when they represent the images of things, appearing at one point of sight, greater than the things themselves. And it is also disproved by double mirrors, which being inclined or turned one towards the other, so that an angle is made within, each of the glasses or plain superficies yields a double resemblance; so that there are four images from the same face, two answerable to the object without on the left side, and two others obscure and not so evident on the right side in the bottom of the mirror. Of which Plato renders the efficient cause; for he says, that a mirror being raised on the one and the other side, the sight varies the reflection, falling from one side to the other. And therefore, since of the views or visions some immediately have recourse to us, and others, sliding to opposite parts of the mirror, do again return upon us from thence, it is not possible that all reflections should be made at equal angles. Though those who closely impugn our opinion contend that, by these reflections of light from the moon upon the earth, the equality of angles is taken away, thinking this to be much more probable than the other.
Nevertheless, if we must of necessity yield and grant thus much to our dearly beloved geometry, first, this should in all likelihood befall those mirrors which are perfectly smooth and exquisitely polished; whereas the moon has many inequalities and roughnesses, so that the rays proceeding from a vast body, and carried to mighty altitudes, receive one from another and intercommunicate their lights, which, being sent to and fro and reciprocally distributed, are refracted and interlaced all manner of ways, and the counter-lights meet one another, as if they came to us from several mirrors. And then, though we should suppose these reflections on the superficies of the moon to be made at equal angles, yet it is not impossible that the rays, coming down unto us by so long an interval, may have their flexions, fractions, and delapsions, that the light being compounded may shine the more. Some also there are who prove by lineary demonstration, that many lights send a ray down by a line drawn below the line of reflection; but to make the description and delineation of it publicly, especially where there were many auditors, would not be very easy.
τὸ δʼ ὅλον ἔφη θαυμάζω πῶς τὴν διχότομον ἐφʼ ἡμᾶς κινοῦσιν, ἐμπίπτουσαν μετὰ τῆς ἀμφικύρτου καὶ τῆς μηνοειδοῦς. εἰ γὰρ αἰθέριον ὄγκον ἢ πύρινον ὄντα τὸν τῆς σελήνης ἐφώτιζεν ὁ ἥλιος, οὐκ ἂν ἀπέλειπεν αὐτῆς σκιερὸν ἀεὶ καὶ ἀλαμπὲς ἡμισφαίριον πρὸς αἴσθησιν, ἀλλʼ εἰ καὶ κατὰ μικρὸν ἔψαυε περιιών, ὅλην ἀναπίμπλασθαι καὶ διʼ ὅλης τρέπεσθαι τῷ φωτὶ πανταχόσε χωροῦντι διʼ εὐπετείας ἦν προσῆκον. ὅπου γὰρ οἶνος ὕδατος θιγὼν κατὰ πέρας, καὶ σταγὼν αἵματος εἰς ὑγρὸν ἐμπεσόντος, ἀνέχρωσε πᾶν ἅμα […] φοινιχθέν· αὐτὸν δὲ τὸν ἀέρα λέγουσιν οὐκ ἀπορροαῖς τισὶν οὐδʼ ἀκτῖσι μεμιγμέναις ἀλλὰ τροπῇ καὶ μεταβολῇ κατὰ νύξιν ἢ ψαῦσιν ἀπὸ τοῦ φωτὸς ἐξηλιοῦσθαι· πῶς ἄστρον ἄστρον καὶ φῶς φωτὸς ἁψάμενον οἴονται μὴ κεράννυσθαι, μηδὲ σύγχυσιν ποιεῖν διʼ ὅλου καὶ μεταβολὴν ἀλλʼ ἐκεῖνα φωτίζειν μόνον, ὧν ἅπτεται κατὰ τὴν ἐπιφάνειαν; ὃν γὰρ ὁ ἥλιος περιιὼν κύκλον ἄγει καὶ περιστρέφει περὶ τὴν σελήνην, νῦν μὲν ἐπιπίπτοντα τῷ διορίζοντι τὸ ὁρατὸν αὐτῆς καὶ τὸ ἀόρατον, νῦν δʼ ἀνιστάμενον πρὸς ὀρθὰς, ὥστε τέμνειν ἐκείνου ὑπʼ ἐκείνου τε τέμνεσθαι, καὶ ἄλλαις κλίσεσι καὶ σχέσεσι τοῦ λαμπροῦ πρὸς τὸ σκιερὸν ἀμφικύρτους καὶ μηνοειδεῖς ἀποδιδόντα μορφὰς ἐν αὐτῇ, παντὸς μᾶλλον ἐπιδείκνυσιν · οὐ σύγκρασιν ἀλλʼ ἐπαφήν, οὐδὲ σύλλαμψιν ἀλλὰ περίλαμψιν αὐτῆς ὄντα; τὸν φωτισμόν. ἐπεὶ δʼ οὐκ αὐτὴ φωτίζεται μόνον ἀλλὰ καὶ δεῦρο τῆς αὐγῆς ἀναπέμπει τὸ εἴδωλον, ἔτι καὶ μᾶλλον ἰσχυρίσασθαι τῷ λόγῳ περὶ τῆς οὐσίας δίδωσιν. αἱ γὰρ ἀνακλάσεις γίγνονται πρὸς οὐδὲν ἀραιὸν οὐδὲ λεπτομερές, οὐδʼ ἔστι φῶς ἀπὸ φωτὸς ἢ πῦρ ἀπὸ πυρὸς ἀφαλλόμενον νοῆσαι ῥᾴδιον· ἀλλὰ δεῖ τὸ ποιῆσον ἀντιτυπίαν τινὰ καὶ κλάσιν ἐμβριθὲς εἶναι καὶ πυκνόν, ἵνα πρὸς αὐτὸ πληγὴ καὶ ἀπʼ αὐτοῦ φορὰ γένηται. τὸν γοῦν αὐτὸν ἥλιον ὁ μὲν ἀὴρ διίησιν οὐ παρέχων ἀνακοπὰς οὐδʼ ἀντερείδων, ἀπὸ δὲ ξύλων καὶ λίθων καὶ ἱματίων εἰς φῶς τιθεμένων πολλὰς ἀντιλάμψεις καὶ περιλάμψεις ἀποδίδωσιν. οὕτω δὲ καὶ τὴν γῆν· ὁρῶμεν ὑπʼ αὐτοῦ φωτιζομένην· οὐ γὰρ εἰς βάθος ὥσπερ ὕδωρ οὐδὲ διʼ ὅλης ὥσπερ ἀὴρ διίησι τὴν αὐγήν· ἀλλʼ οἷος τὴν σελήνην περιστείχει κύκλος αὐτοῦ καὶ ὅσον ὑποτέμνεται μέρος ἐκείνης, τοιοῦτος ἕτερος; περίεισι τὴν γῆν καὶ τοσοῦτον φωτίζων ἀεὶ καὶ ἀπολείπων ἕτερον ἀφώτιστον· ἡμισφαιρίου γὰρ ὀλίγῳ δοκεῖ μεῖζον εἶναι τὸ περιλαμπόμενον ἑκατέρας. δότε δή μοι γεωμετρικῶς εἰπεῖν πρὸς ἀναλογίαν, ὡς εἰ, τριῶν ὄντων οἷς τὸ ἀφʼ ἡλίου φῶς πλησιάζει, γῆς σελήνης; ἀέρος, ὁρῶμεν οὐχ ὡς ὁ ἀὴρ μᾶλλον ἢ ὡς ἡ γῆ φωτιζομένην τὴν σελήνην, ἀνάγκη φύσιν ἔχειν ὁμοίαν ἃ ταὐτὰ πάσχειν ὑπὸ ταὐτοῦ πέφυκεν.
But in brief, said he, I wonder how they come thus to allege against us the half-moon, there being the same reason when she is gibbous and crescent. For if the sun enlightened the moon, as a mass of ethereal or fiery matter, he would never surely leave one hemisphere, or half of her globe always appearing dark and shadowy to sense, as it is seen to be; but how little soever he touched her superficies, it would be agreeable to reason that it should be wholly replenished and totally changed by that light of his, which by reason of its agility and swiftness so easily spreads and passes through all. For, since wine touching water only in one point, or one drop of blood falling into any liquor, dyes and colors it all with a red or purple color; and since they say, that the very air is altered and changed with light, not by any defluxions or beams intermingled, but by a sudden conversion and change made in one only point; how can they imagine that one star touching another star, and one light another light, should not be immediately mingled, nor make any thorough confusion or change, but only exteriorly illuminate that whose superficies it touches? For that circle which the sun makes by fetching a compass and turning towards the moon,—sometimes falling upon the very line that distinguishes her visible part from her invisible, and sometimes rising up directly, so that it cuts her in two and is reciprocally cut by her, causing in her, by several inclinations and habitudes of the luminous to the dark, those various forms by which she appears gibbous and crescent,—that more than any thing else demonstrates, that all this illumination of the moon is not a mixture, but only a touching; nor a conflux or gathering together of sundry lights, but only an illustration round about.
But forasmuch as she is not only enlightened herself, but also sends back hither the image of her illumination, this confirms us yet further in what we say touching her substance. For reflections and reverberations are not made upon any thing which is rare, and of thin and subtile parts; nor is it easily to be imagined how light can rebound from light, or one fire from another. But that which is to make the reverberation or reflection must be solid and firm, that a blow may be given against it and a rebounding made from it. As a proof of this, we see that the air transmits the sun, and gives him a way to pierce quite through it, not obstructing or driving back his rays; but on the contrary from wood, stones, or clothes put in the sun, there are made many reflections of light and many illuminations round about. So we see that the earth is illuminated by him, not to the very bottom, as the water, nor thoroughly and all over, as the air, through which the beams of the sun have a clear passage; but just such a circle as surrounds the moon surrounds also the earth; and as much of the earth as this circle includes, so much does the sun enlighten, the rest being left without light; for what is illuminated both in the one and in the other is little more than an hemisphere. Permit me therefore now to conclude after the manner of geometricians by proportions. If there are three things which the light of the sun approaches, the air, the moon, and the earth, and if we see that the moon is enlightened by him, not as the air, but as the earth, it is of necessity that those two things must have one and the same nature, which of one and the same cause suffer the same effects.
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