All round as fire she shines, but in her midst,
Bluer than cyanus, lo, a maiden’s eye,
Her tender brow, her face in counterpart.
For the shadowy parts really pass beneath the bright ones which they encircle, and in turn press and are cut off by them; thus light and shade are interwoven throughout, and the face-form |F| is delineated to the life. The argument was thought to meet your Clearchus also, Aristotle, no less unanswerably; for yours he is, and an intimate of your namesake of old, although he perverted many doctrines of the Path.’
III. Here Apollonides interposed to ask what the view of Clearchus was. ‘No man’, I said, ‘has less good right than you to ignorance of a doctrine which starts from geometry, |921| as from its native hearth. Clearchus says that the face, as we call it, is made up of images of the great ocean mirrored in the moon. For our sight[[304]] being reflected back from many points, is able to touch objects which are not in its direct line; and the full moon is of all mirrors the most beautiful and the purest in uniformity and lustre. As then you geometers think that the rainbow is seen in the cloud when it has acquired a moist and smooth consistence, because our vision is reflected on to the sun,[[305]] so Clearchus held that the outer ocean is seen |B| in the moon, not where it really is, but in the place from which reflexion carried our sight into contact with it and its dazzle. Agesianax has another passage:
Or ocean’s wave that foams right opposite,
Be mirrored like a sheet of fire and flame.’
IV. This pleased Apollonides. ‘What a fresh way of putting a view; that was a bold man, and there was poetry in him. But how did the refutation proceed on your side?’ ‘In this way’, I answered. ‘First, the outer ocean is uniform, a sea with one continuous stream, whereas the appearance of the dark places in the moon is not uniform; there are isthmuses, so to call them, where the brightness parts and |C| defines the shadow; each region is marked off and has its proper boundary, and so the places where light and shade meet assume the appearance of height and depth, and represent very naturally human eyes and lips. Either, therefore, we must assume that there are more oceans than one, parted by real isthmuses and mainlands, which is absurd and untrue; or, if there is only one, it is impossible to believe that its image could appear thus broken up. Now comes a question which it is safer to ask in your presence than it is to state an answer. Given that the habitable world is “equal in breadth and length”,[[306]] is it possible that the view of the sea as a whole, thus reflected from the moon, |D| should reach those sailing upon the great sea itself, yes, or living on it as the Britons do, and this even if the earth does, as you said that it does, occupy a point central to the sphere in which the moon moves?[[307]] This’, I continued, ‘is a matter for you to consider, but the reflexion of vision from the moon is a further question which it is not for you to decide, nor yet for Hipparchus. I know, my dear friend [that Hipparchus is a very great astronomer], but many people do not accept his view on the physical nature of vision, since it is probably a sympathetic |E| blending and commixture, rather than a succession of strokes and recoils such as Epicurus devised for his atoms. Nor will you find Clearchus ready to assume with you that the moon is a weighty and solid body. Yet “an ethereal and luminous star”, to use your words, ought to break and divert the vision, so there is no question of reflexion. Lastly, if any one requires us to do so, we will put the question, how is it that only one face is seen, the sea mirrored on the moon, and none in any of all |F| the other stars? Yet reason demands that our vision should be thus affected in the case of all or of none. But now,’ I said, turning to Lucius, ‘remind us which of our points was mentioned first.’
V. ‘No;’ said Lucius, ‘to avoid the appearance of merely insulting Pharnaces, if we pass over the Stoic view without a word of greeting, do give some answer to Clearchus, and his assumption that the moon is a mere mixture of air and mild fire, that the air grows dark on its surface, as a ripple courses over a calm sea, and so the appearance of a face is produced.’
‘It is kind of you, Lucius,’ I said, ‘to clothe this absurdity in sounding terms. That is not how our comrade dealt with it. He said the truth, that it is a slap in the face to the moon when they fill her with smuts and blacks, addressing her in one breath |922| as Artemis and Athena,[[308]] and in the very same describing a caked compound of murky air and charcoal fire, with no kindling or light of its own, a nondescript body smoking and charred like those thunderbolts which poets[[309]] address as “lightless” and “sooty”. That a charcoal fire, such as this school makes out the moon to be, has no stability or consistence at all, unless |B| it find solid fuel at once to support and to feed it, is a point not so clearly seen by some philosophers as it is by those who tell us in jest that Hephaestus has been called lame because fire progresses no better without wood than lame people without a stick! If then the moon is fire, whence has it all this air inside it? For this upper region, always in circular motion, belongs not to air but to some nobler substance, which has the property of refining and kindling all things. If air has been generated, how is it that it has not been vaporized by the fire and passed away into some other form, but is preserved near fire all this time, like a nail fitted into the same place and wedged there for ever? If it is rare and diffused, |C| it should not remain stable, but be displaced. On the other hand, it cannot subsist in a solidified form, because it is mingled with fire, and has neither moisture with it nor earth, the only agents by which air can be compacted. Again, rapid motion fires the air which is contained in stones, and even in cold lead, much more then that which is in fire, when whirled round with such velocity. For they are displeased with Empedocles, when he describes the moon as a mass of air frozen like hail and enclosed within her globe of fire. Yet they themselves hold that the moon is a globe of fire which encloses air variously distributed, and this though they do not allow that she has |D| clefts in herself, or depths and hollows (for which those who make her an earth-like body find room), but clearly suppose that the air lies upon her convex surface. That it should do so is absurd in point of stability, and impossible in view of what we see at full moon; for we ought not to be able to distinguish black parts and shadow then; either all should be dull and shrouded, or all should shine out together when the moon is caught by the sun. For look at our earth; the air which lies in her depths and hollows, where no ray penetrates, remains in shadow unilluminated; that which is outside, diffused over the earth, has light and brilliant colouring, because from its rarity it easily mingles, and takes up any quality or influence. |E| By light, in particular, if merely touched, or, in your words, grazed, it is changed all through and illumined. This is at once an excellent ally to those who thrust the air into depths and gullies on the moon, and also quite disposes of you, who strangely compound her globe of air and fire. For it is impossible |F| that shadow should be left on her surface when the sun touches with his light all that part of the moon which is framed within our own field of vision.’