This third argument of M. Cousin is the same as that which I have already examined in remarking upon M. Boeckh. The diurnal rotation of the earth cannot stand in the same astronomical system with the diurnal rotation of the sidereal sphere. Incontestably true (I have already said) as a point of science. But the question here is, not what opinions are scientifically consistent, but what opinions were held by Plato, and whether he detected the inconsistency between the two. I have shown grounds for believing that he did not — and not he alone, but many others along with him, Aristotle among the number. How, indeed, can this be denied, when we find M. Boeckh announcing that he is the first among all the critics on the Timæus, who has brought forward the inconsistency as a special ground for determining what Plato’s opinion was — that no other critic before him had noticed it?
The first words of this argument deserve particular attention, “Si la terre suit le mouvement de l’axe du monde.” Here we have an exact recital of the doctrine proclaimed by the Platonic Timæus, and ascribed to him by Aristotle (quite different from the doctrine “que la terre tourne sur elle-même”). M. Cousin here speaks very distinctly about the cosmical axis, and about its movement; thus implying that Plato conceived it as a solid revolving cylinder. This, in my judgment, is the most essential point for clearing up the question in debate. The cosmical axis being of this character, when Plato affirms that the earth is packed or fastened round it (se roule — Cousin: se serre et s’enroule — Martin: drängt sich, macht eine Kugel um ihn — Buttmann), I maintain that, in the plainest construction of the word, the earth does and must follow the movement of the axis — or arrest the movement of the axis. The word εἱλομένην or ἰλλομένην has no distinct meaning at all, if it does not mean this. The very synonyms (σφιγγομένην, περιδεδεμένην, &c.), which the commentators produce to prove that Plato describes the earth as at rest, do really prove that he describes it as rotating round and with the cosmical axis. We ought not to be driven from this plain meaning of the word, by the assurance of M. Cousin and others that Plato cannot have meant so, because it would involve him in an astronomical inconsistency.
4. “Les divers mouvemens des huit sphères expliquent toutes les apparences célestes; il n’y a donc aucune raison pour donner un mouvement à la terre.”
The terms of this fourth argument, if literally construed, would imply that Plato had devised a complete and satisfactory astronomical theory. I pass over this point, and construe them as M. Cousin probably intended: his argument will then stand thus — “The movement of the earth does not add anything to Plato’s power of explaining astronomical appearances; therefore Plato had no motive to suggest a movement of the earth.”
I have already specified the sense in which I understand the Platonic Timæus to affirm, or rather to imply, the rotation of the earth; and that sense is not open to the objections raised in M. Cousin’s fourth and fifth arguments. The rotation of the earth, as it appears in the Platonic Timæus, explains nothing, and is not intended to explain anything. It is a consequence, not a cause: it is a consequence arising from the position of the earth, as packed or fastened round the centre of the cosmical axis, whereby the earth participates, of necessity and as a matter of course, in the movements of that axis. The function of the earth, thus planted in the centre of the kosmos, is to uphold and regulate the revolutions of the cosmical axis; and this function explains, in the scheme of the Platonic Timæus, why the axis revolves uniformly and constantly without change or displacement. Now upon these revolutions of the cosmical axis all the revolutions of the exterior sphere depend. This is admitted by M. Cousin himself in argument 3. There is therefore every reason why Plato should assign such regulating function to the earth, the “first and oldest of intra-kosmic deities.” The movement of the earth (as I before observed) is only an incidental consequence of the position necessary for the earth to occupy in performing such function.
5. “Enfin Platon assigne un mouvement aux étoiles fixes, et deux mouvemens aux planètes; puisqu’il ne range la terre ni avec les unes ni avec les autres, il y a lieu de croire qu’elle ne participe à aucun de leurs mouvemens.”
In so far as this argument is well-founded, it strengthens my case more than that of M. Cousin. The earth does not participate in the movements either of the fixed stars or of the planets; but it does participate in the revolutions of the cosmical axis, upon which these movements depend — the movements of the outer sphere, wholly and exclusively — the movements of the planets, to a very great degree, but not exclusively. The earth is not ranked either among the fixed stars or among the planets; it is a body or deity sui generis, having a special central function of its own, to regulate that cosmical axis which impels the whole system. The earth has a motion of its own, round and along with the cosmical axis to which it is attached; but this motion of the earth (I will again repeat, to prevent misapprehension) is a fact not important by itself, nor explaining anything. The grand and capital fact is the central position and regulating function of the earth, whereby all the cosmical motions, first those of the axis, next those of the exterior kosmos, are upheld and kept uniform.
M. Cousin adds, as a sixth argument:—
“On peut ajouter à ces raisons que Platon aurait nécessairement insisté sur le mouvement de la terre, s’il l’avait admis; et que ce point étoit trop controversé de son temps et trop important en lui-même, pour qu’il ne fît que l’indiquer en se servant d’une expression équivoque.”
In the first place, granting Plato to have believed in the motion of the earth, can we also assume that he would necessarily have asserted it with distinctness and emphasis, as M. Cousin contends? I think not. Gruppe maintains exactly the contrary; telling us that Plato’s language was intentionally obscure and equivocal — from fear of putting himself in open conflict with the pious and orthodox sentiment prevalent around him. I do not carry this part of the case so far as Gruppe, but I admit that it rests upon a foundation of reality. When we read (Plutarch, De Facie in Orbe Lunæ, p. 923) how the motion of the earth, as affirmed by Aristarchus of Samos (doubtless in a far larger sense than Plato ever imagined, including both rotation and translation), was afterwards denounced as glaring impiety, we understand the atmosphere of religious opinion with which Plato was surrounded. And we also perceive that he might have reasons for preferring to indicate an astronomical heresy in terms suitable for philosophical hearers, rather than to proclaim it in such emphatic unequivocal words, as might be quoted by some future Melêtus in case of an indictment before the Dikasts.