Concerning the Face which Appears in the Orb Of the Moon (15-19)

Such is probably the case with the cosmos too, if it really is a living being[*]: in many places it has

earth and in many fire and water and breath as the result not of forcible expulsion[*] but of rational arrangement. After all, the eye has its present position in the body not because it was extruded thither as a result of its lightness, and the heart is in the chest not because its heaviness has caused it to slip and fall thither but because it was better that each of them should be so located. Let us not then believe with regard to the parts of the cosmos either that earth is situated here because its weight has caused it to subside or that the sun, as Metrodorus of Chios[*] once thought, was extruded into the upper region like an inflated skin by reason of its lightness or that the other stars got into their present positions because they tipped the balance, as it were, at different weights. On the contrary, the rational principle is in control; and that is why the stars revolve fixed like radiant eyes [*] in the countenance of the universe, the sun in the hearts capacity transmits and disperses out of himself heat and light as it were blood and breath, and earth and sea naturally serve the cosmos to the ends that bowels and bladder do an animal. The moon, situate between sun and earth as the liver or another of the soft viscera[*] is between heart and bowels, transmits hither the warmth from above and sends upwards the exhalations from our region, refining them in herself by a kind of concoction and purification.[*] It is not clear to us whether her earthiness and solidity have any use suitable to other ends also. Nevertheless, in everything the better has control of the necessary.[*] Well, what probability can we thus conceive in the statements of the Stoics? They say that the luminous and tenuous part of the ether by reason of its subtility became sky and the part which was condensed or compressed became stars, and that of these the most sluggish and turbid is the moon.[*] Yet all the same anyone can see that the moon has not been separated from the ether but that there is still a large amount of it about her in which she moves and much of it beneath her in which [they themselves assert that the bearded stars] and comets whirl. So it is not the inclinations consequent upon weight and lightness that have circumscribed the precincts[*] of each of the bodies, but their arrangement is the result of a different principle.

With these remarks I was about to yield the floor to Lucius,[*] since the proofs of our position were next in order; but Aristotle smiled and said: The company is my witness that you have directed your entire refutation against those who suppose that the moon is for her part semi-igneous and yet assert of all bodies in common that of themselves they incline either upwards or downwards. Whether there is anyone, however, who says[*] that the stars move naturally in a circle and are of a substance far superior to the four substances here[*] did not even accidentally come to your notice, so that I at any rate have been spared trouble. And Lucius [broke in and] said: ⋯good friend, probably one would not for the moment quarrel with you and your friends, despite the countless difficulties involved, when you ascribe to the other stars and the whole heaven a nature pure and undefiled and free from qualitative change and

moving in a circle whereby [it is possible to have the nature] of endless revolution too; but let this doctrine descend and touch the moon, and in her it no longer preserves the impassivity and beauty of that body. Not to mention her other irregularities and divergencies, this very face which she displays is the result of some alteration of her substance or of the admixture somehow of another substance.[*] That which is subjected to mixture, however, is the subject of some affection too, for it loses its purity, since it is perforce infected by what is inferior to it. The moon’s sluggishness and slackness of speed and the feebleness and faintness of her heat [which], in the words of Ion,

ripes not the grape to duskiness,[*]

to what shall we ascribe them except to her weakness and alteration, [if] an eternal and celestial[*] body can have any part in [alteration]? The fact is in brief, my dear Aristotle, that regarded as earth the moon has the aspect of a very beautiful, august, and elegant object; but as a star or luminary or a divine and heavenly body she is, I am afraid, misshapen, ugly, and a disgrace to the noble title, if it is true that of all the host in heaven she alone goes about in need of alien light,[*] as Parmenides says Fixing her glance forever on the sun.[*] Our comrade in his discourse[*] won approval by his demonstration of this very proposition of Anaxagorass that the sun imparts to the moon her brilliance [*]; for my part, I shall not speak about these matters that I learned from you or in your company but shall gladly proceed to what remains. Well then, it is plausible that the moon is illuminated not by the suns irradiating and shining through her in the manner of glass[*] or ice[*] nor again as the result of some sort of concentration of brilliance or aggregation of rays, the light increasing as in the case of torches.[*] Were that true, we should see the moon at the full on the first of the month no less than in the middle of the month, if she does not conceal and obstruct the sun but because of her subtility lets his light through or as a result of combining with it flashes forth and joins in kindling the light in herself.[*] Certainly her deviations or aversions[*] cannot be alleged as the cause of her invisibility when she is in conjunction, as they are when she is at the half and gibbous or crescent; then, rather, standing in a straight line with her illuminant, says Democritus, she sustains and receives the sun, [*] so that it would be reasonable for her to be visible and to let him shine through. Far from doing this, however, she is at that time invisible herself and often has concealed and obliterated him.

His beams she put to flight,

as Empedocles says,

From heaven above as far as to the earth,

Whereof such breadth as had the bright-eyed moon

She cast in shade,[*]

just as if the light had fallen into night and darkness and not upon an other star. As for the explanation of Posidonius that the profundity of the moon prevents the light of the sun from passing through her to us,[*] this is obviously refuted by the fact that the air, though it is boundless and has many times the profundity of the moon, is in its entirety illuminated and filled with sunshine by the rays. There remains then the theory of Empedocles that the moonlight which we see comes from the moons reflection of the sun. That is why there, is neither warmth[*] nor brilliance in it when it reaches us, as we should expect there to be if there had been a kindling or mixture of [the] lights [of sun and moon].[*] To the contrary, just as voices when they are reflected produce an echo which is fainter than the original sound and the impact of missiles after a ricochet is weaker,

Thus, having struck the moon’s broad disk, the ray[*]

comes to us in a refluence weak and faint because the deflection slackens its force.

Sulla then broke in and said: No doubt this position has its plausible aspects; but what tells most strongly on the other side, did our comrade[*] explain that away or did he fail to notice it? What’s that? said Lucius, or do you mean the difficulty with respect to the half-moon? Exactly, said Sulla, for there is some reason in the contention that, since all reflection occurs at equal angles,[*] whenever

the moon at the half is in mid-heaven the light cannot move earthwards from her but must glance off beyond the earth. The ray that then touches the moon comes from the sun on the horizon[*] and therefore, being reflected at equal angles, would be produced to the point on the opposite horizon and would not shed its light upon us, or else there would be great distortion and aberration of the angle, which is impossible. [*] Yes, by Heaven, said Lucius, there was talk of this too; and, looking at Menelaus the mathematician as he spoke, he said: In your presence, my dear Menelaus, I am ashamed to confute a mathematical proposition, the foundation, as it were, on which rests the subject of catoptrics. Yet it must be said that the proposition, all reflection occurs at equal angles, [*] is neither self-evident nor an admitted fact.[*] It is refuted in the case of convex[*] mirrors when the point of incidence of the visual ray produces images that are magnified in one respect; and it is refuted by folding mirrors,[*] either plane of which, when they have been inclined to each other and have formed an inner angle, exhibits a double image, so that four likenesses of a single object are produced, two reversed on the outer surfaces and two dim ones not reversed in the depth of the mirrors. The reason for the production of these images Plato explains,[*] for he has said that when the mirror is elevated on both sides the visual rays interchange their reflection because they shift from one side to the other. So, if of the visual rays (some) revert straight to us (from the plane surfaces) while others glance off to the opposite sides of the mirrors and thence return to us again, it is not possible that all reflections occur at equal angles.[*] Consequently (some people) take direct issue (with the mathematicians) and maintain that they confute the equality of the angles of incidence and reflection by the very streams of light that flow from the moon upon the earth, for they deem this fact to be much more credible than that theory. Nevertheless, suppose that this[*] must be conceded as a favour to geometry, the dearly beloveds3 In the first place, it is likely to occur only in mirrors that have been polished to exact smoothness; but the moon is very uneven and rugged, with the result that the rays from a large body striking against considerable heights which receive reflections and diffusions of light from one another are multifariously reflected and intertwined and the refulgence itself combines with itself, coming to us, as it were, from many mirrors. In the second place, even if we assume that the reflections on the surface of the moon occur at equal angles, it is not impossible that the rays as they travel through such a great interval get fractured and deflected[*] so as to be blurred and to bend their light. Some people even give a geometrical demonstration that the moon sheds many of her beams upon the earth along a line extended from the surface that is bent away from us[*]; but I could not construct a geometrical diagram while talking, and talking to many people too.

Speaking generally, he said, I marvel that they adduce against us the moon’s shining upon the earth at the half and at the gibbous and the crescent phases too.[*] After all, if the mass of the moon that is illuminated by the sun were ethereal or fiery, the

sun would not leave her[*] a hemisphere that to our perception is ever in shadow and unilluminated; on the contrary, if as he revolves he grazed her ever so slightly, she should be saturated in her entirety and altered through and through by the light proceeding easily in all directions. Since wine that just touches water at its surface[*] or a drop of blood fallen into liquid at the moment [of contact] stains all the liquid red,[*] and since they say that the air itself is filled with sunshine not by having any effluences or rays commingled with it but by an alteration and change that results from impact or contact of the light,[*] how do they imagine that a star can come in contact with a star or light with light and instead of blending and producing a thorough mixture and change merely illuminate those portions of the surface which it touches?[*] In fact, the circle which the sun in its revolution describes and causes to turn about the moon now coinciding with the circle that divides her visible and invisible parts and now standing at right angles to it so as to intersect it and be intersected by it, by different inclinations and relations of the bright part to the dark producing in her the gibbous and crescent phases,[*] conclusively demonstrates that her illumination is the result not of combination but of contact, not of a concentration of light within her but of light shining upon her from without. In that she is not only illuminated herself, however, but also transmits to us the semblance of her illumination, she gives us all the more confidence in our theory of her substance. There are no reflections from anything rarefied or tenuous in texture, and it is not easy even to imagine light rebounding from light or fire from fire; but whatever is to cause a repercussion or a reflection must be compact and solid,[*] in order that it may stop a blow and repel it.[*] At any rate, the same sunlight that the air lets pass without impediment or resistance is widely reflected and diffused from wood and stone and clothing exposed to its rays. The earth too we see illuminated by the sun in this fashion. It does not let the light penetrate its depths as water does or pervade it through and through as air does; but such as is the circle of the sun that moves around the moon and so great as is the part of her that it intercepts, just such a circle in turn moves around the earth, always illuminating just so much and leaving another part unilluminated,[*] for the illuminated portion of either body appears to be slightly greater than a hemisphere.[*] Give me leave then to put it in geometrical fashion in terms of a proportion. Given three things approached by the light from the sun: earth, moon, air; if we see that the moon is illuminated not as the air is rather than as the earth, the things upon which the same agent produces the same effects must be of a similar nature. [*]

When all had applauded Lucius, I said: Congratulations upon having added to an elegant account an elegant proportion, for you must not be defrauded of what belongs to you, He smiled thereat and said: Well then proportion must be used a second time, in order that we may prove the moon to be like the earth not only because the effects of the same agent are the same on both but also because the effects of both on the same patient are the same. Now, grant me that nothing that happens to the sun is so like its setting as a solar eclipse. You will if you call to mind this conjunction recently which, beginning just after noonday, made many stars shine out from many parts of the sky[*] and tempered the air in the manner of twilight.[*] If you do not recall it, Theon here will cite us Mimnermus[*] and Cydias[*] and

Archilochus[*] and Stesichorus besides and Pindar,[*] who during eclipses bewail the brightest star bereft [*] and at midday night falling [*] and say that the beam of the sun [is sped] the path of shade [*]; and to crown all he will cite Homer, who says the faces of men are covered with night and gloom[*] and the sun has perished out of heaven[*] speaking with reference to the moon and [hinting that] this naturally occurs

When waning month to waxing month gives say.[*]

For the rest, I think that it has been reduced by the precision of mathematics to the [clear] and certain [formula] that night is the shadow of earth[*] and the eclipse of the sun is the shadow of the moon[*] whenever the visual ray encounters it. The fact is that in setting the sun is screened from our vision by the earth and in eclipse by the moon; both are cases of occultation, but the vespertine is occultation by the earth and the ecliptic by the moon with her shadow intercepting the visual ray.[*] What follows from this is easy to perceive. If the effect is similar, the agents are similar, for it must be the same agents that cause the same things to happen to the same subject. Nor should we marvel if the darkness of eclipses is not so deep or so oppressive of the air as night is. The reason is that the body which produces night and that which produces the eclipse while the same in substance are not equal in size. In fact the Egyptians, I think, say that the moon is one seventy-second part (of the earth),[*] and Anaxagoras that it is the size of the Peloponnesus[*]; and Aristarchus demonstrates that the ratio of [the earth’s diameter to] the diameter of the moon is smaller than 60 to 19 and greater than 108 to 43.[*] Consequently the earth because of its size removes the sun from sight entirely, for the obstruction is large and its duration is that of the night. Even if the moon, however, does sometimes cover the sun entirely, the eclipse does not have duration or extension; but a kind of light is visible about the rim which keeps the shadow from being profound and absolute.[*] The ancient Aristotle gives this as a reason besides some others why the moon is observed in eclipse more frequently than the sun, saying that the sun is eclipsed by interposition of the moon but the moon [by that of the earth, which is much larger].[*] Posidonius gave this definition: The following condition is an eclipse of the sun, conjunction of the moon’s shadow with whatever [parts of the earth it may obscure], for there is an eclipse only for those whose visual ray the shadow of the moon intercepts and screens from the sun[*]; — since he concedes then that a shadow of the moon falls upon us, he has left himself nothing to say that I can see. Of a star there can be no shadow, for shadow means the unlighted and light does not produce shadow but naturally destroys it.[*]