Hence we must consider the agency of the stars as analogous to that of plants and animals. For here the agency of man is most multifarious, since he is capable of attaining many varieties of good, and accordingly busies himself about many things and about one thing for the sake of others. The agency of other animals on the other hand is more restricted; that of plants yet more so, being of slight force and only of one special character (s. 4). But that which exists in the best possible condition stands in no need of acting or agency; for it already possesses that for the sake of which action is undertaken. Now action always includes two elements — that for the sake of which and what is for the sake thereof — the end and the means: there is either some one end, which the agent may attain, as in the case of man; or there are many different matters all of which may be used as means towards the best possible condition. Thus one agent possesses and partakes of the best possible condition; another comes near to it with little trouble; a third, with much trouble; a fourth does not even aspire to the end, but is competent only to arrive near to the last of the means. For example, let health be the end: one man is always in health; a second becomes so, by being starved down; a third by that, combined with running exercise; a fourth is obliged to take some additional exercise, in order to qualify himself for running, so that his motions are multiplied; a fifth is incapable of arriving at health, but arrives only at the running and the being thinned down, one of which in this case serves as end. For it would be best for all, if they could attain the supreme end — health; but, if that be impossible, then the next best thing is to get as near to the best as possible (ss. 5-7).
For this reason the Earth is not moved at all, and the matters near the Earth are moved with few motions; since they do not arrive at the extreme best, but only as near as their ability permits to obtain or hit the supremely divine principle; while the First Heaven, on the contrary, obtains or hits it at once, through one single motion; and the bodies intermediate between the First Heaven and those which are last (or nearest to the Earth), obtain it or arrive at it also, but only through a greater number of motions.
There is the other difficulty also to be considered — that vast multitude of stars are put all together in the one single First Current or Revolution, but each of the other stars (planets) has its own motions singly and apart. The principal reason of this we may fairly suppose to be that it follows as a natural consequence from the vast superiority of the first, in each variety of life and in each beginning, over all posterior to the first. Here the First Current or Revolution, being one and by itself, moves many of the divine bodies, while the others (secondary or countercurrents), numerous as they are, move each only one; for each one of these wandering bodies or planets is carried by many different currents. Thus Nature establishes equalization and a sort of symmetry, by assigning, in the one case, many bodies to one current, and in the other, many currents to one body (ss. 8-10). Beside this principal reason, there is also another. The other currents have each one body only, because motion is given to many bodies by all of them prior to the last which bears the one star. For the last sphere is carried round fastened into many spheres, and each sphere is a body (ss. 11, 12. I do not clearly understand the lines that follow:— ἐκείνης ἂν οὖν κοινὸν εἴη τὸ ἔργον· αὕτη μὲν γὰρ ἑκάστῃ ἡ ἴδιος φύσει φορά· αὕτη δὲ οἷον προσκεῖται. παντὸς δὲ πεπερασμένου σώματος πρὸς πεπερασμένον ἡ δύναμίς ἐστιν.).[1]
[1] [See Prantl’s note on this difficult passage in his German translation of the De Cœlo, p. 309 (Leipzig, 1857).]
CH. 13. — Having thus explained, respecting the Stars and Planets which are carried round in circular motion, what is their essence, figure, current, and order of position, we now proceed to speak of the Earth: What is its position? Whether is it at rest or in motion? What is its figure?
Philosophers differ respecting the position of the Earth. Most of those who conceive the entire Kosmos as finite, declare the Earth to be in its centre. But the Italian philosophers, called Pythagoreans, are of an opposite opinion; affirming that Fire is in the centre, and that the Earth, being one of the stars revolving round the centre, makes night and day. They assume moreover another Earth opposite to this (ἐναντίαν ἄλλην ταύτῃ) — which other they call Antichthon. Herein they do not adjust their theories and look out for causes adapted to the phenomena; but, on the contrary, they distort the phenomena so as to suit their own doctrines and reasonings, and try to constitute themselves auxiliary governors of the Kosmos (πειρώμενοι συγκοσμεῖν — s. 1). And, if we are to look for assurance not to the phenomena but to our own reasonings, many others might agree with them, that it is not proper (μὴ δεῖν) to assign to the Earth the central place. They think that the most honourable place belongs to the most honourable body, and that Fire is more honourable than Earth; that the two extremes, centre and circumference, are more honourable than the parts intermediate between them. Upon these grounds they consider that Fire and not Earth is at the centre of the Universal Sphere; and they have another reason, peculiar to themselves, for this conclusion: they hold that the centre is the most important place in the universe, and that it ought as such to be the most carefully guarded; wherefore they call it the watch of Zeus (Διὸς φυλακήν), and regard it as occupied by Fire (s. 2).
This assumes that what is absolutely (i.e., without subjoining any qualifying adjunct), described as the centre, is at once centre of the magnitude, centre of the object, and centre of nature. But we ought rather to follow the analogy of animals, where the same point is not the centre of the animal and the centre of the body: the case is the same in the entire Kosmos. Hence the Pythagoreans need not feel any anxiety about the Universe (οὐθὲν αὐτοὺς δεῖ θορυβεῖσθαι περὶ τὸ πᾶν), nor introduce a guard at the centre. They ought rather to enquire where and of what character the middle point is; for that middle point is the true beginning and the honourable. The middle of the place occupied is rather like an end than like a beginning; for that which is limited is the middle, that which limits is the boundary: now that which comprehends and is boundary, is more honourable than that which is bounded; the former is the Essence of the entire compound, the latter is only its Matter (s. 3).
As about the place of the Earth, so also about its motion or rest, philosophers differ. The Pythagoreans and those who do not even place it at the centre, consider it to revolve in a circle, and they consider the Antichthon to revolve in like manner. Some even think it possible that there may be many other bodies carried round the centre in like manner, though invisible to us, by reason of the obstructing body of the Earth. Hence (they say) the eclipses of the moon are more frequent than those of the Sun; since not only the Earth, but also each of these unseen bodies, causes the Moon to be eclipsed. For, the Earth not being a point, we on the circumference thereof, even assuming it to occupy the centre, are distant from the centre by the entire hemisphere of the Earth; yet we do not find out that we are not in the centre, and astronomical appearances present themselves to us just as if we were so. Thus it happens (according to these philosophers), the Earth not being in the centre at all: the appearances presented to us are just the same as if we were at the centre.
Again, there are some who (like Plato in Timæus) affirm that the Earth, though situated in the centre, is packed and revolves round the axis stretched across the universe (s. 4).
About the figure of the Earth, there is no less difference of opinion. Some say that it is spherical; others, that it is flat and in shape like a tambourine (τυμπανοειδής). These last adduce as proof, that the Sun, at rising and setting, exhibits a rectilinear section or eclipse of his disk and not a circular one, when partially concealed by the Earth, and becoming invisible under the horizon or visible above the horizon. They do not take proper account of the vast distance of the Sun and the magnitude of his circumference. The segment of a long circle appears from a distance like a straight line. These philosophers further add, that the flat tambourine-like shape must be inferred of necessity from the fact that the Earth remains stationary (s. 5).