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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.
