As applied to any person educated in the modern astronomy, the argument is irresistible. But is it equally irresistible when applied to Plato and to Plato’s time? I think not. The incompatibility which appears so glaring at present, did not suggest itself to him or to his contemporaries. To prove this we have only to look at the reasoning of Aristotle, who (in the treatise De Cœlo, ii. 13-14, p. 293. b. 30, 296. a. 25) notices and controverts the doctrine of the rotation of the earth, with express reference to the followers of the Platonic Timæus — and who (if we follow the view of Martin) imputes this doctrine with wilful falsehood to Plato, for the purpose of contemptuously refuting it “pour se donner le plaisir de la réfuter avec dédain.” Granting the view of M. Boeckh (still more that of Martin) to be correct, we should find Aristotle arguing thus:— “Plato affirms the diurnal rotation of the earth round the centre of the cosmical axis. This is both incredible, and incompatible with his own distinct affirmation that the sidereal sphere revolves in twenty-four hours. It is a glaring inconsistency that the same author should affirm both the one and the other.” Such would have been Aristotle’s reasoning, on the hypothesis which I am considering; but when we turn to his treatise we find that he does not employ this argument at all. He contests the alleged rotation of the earth upon totally different arguments — chiefly on the ground that rotatory motion is not natural to the earth, that the kind of motion natural to the earth is rectilineal, towards the centre; and he adds various corollaries flowing from this doctrine which I shall not now consider. At the close of his refutation, he states in general terms that the celestial appearances, as observed by scientific men, coincided with his doctrine.
Hence we may plainly see that Aristotle probably did not see the incompatibility, supposed to be so glaring, upon which M. Boeckh’s argument is founded. To say the least, even if he saw it, he did not consider it as glaring and decisive. He would have put it in the foreground of his refutation, if he had detected the gross contradiction upon which M. Boeckh insists. But Aristotle does not stand alone in this dulness of vision. Among the various commentators, ancient and modern, who follow him, discussing the question now before us, not one takes notice of M. Boeckh’s argument. He himself certifies to us this fact, claiming the argument as his own, and expressing his astonishment that all the previous critics had passed it over, though employing other reasons much weaker to prove the same point. We read in M. Boeckh’s second ‘Commentatio de Platonico Systemate Cœlestium Globorum et de Verâ Indole Astronomiæ Philolaicæ,’ Heidelberg, 1810, p. 9, the following words:—
“Non moveri tellurem, Proclus et Simplicius ostendunt ex Phædone. Parum firmum tamen argumentum est ex Phædone ductum ad interpretandum Timæi locum: nec melius alterum, quod Locrus Timæus, quem Plato sequi putabatur, terram stare affirmat: quia, ut nuper explicuimus, non Plato ex Locro, sed personatus Locrus ex Platone, sua compilavit. At omnium firmissionum et certissimum argumentum ex ipso nostro dialogo sumptum, adhuc, quod jure mirere, nemo reperit. Etenim, quum, paulo supra, orbem stellarum fixarum, quem Græci ἀπλανῆ appellant, dextrorsum ferri quotidiano motu Plato statuebat, non poterat ullum terræ motum admittere; quia, qui hunc admittit, illum non tollere non potest.” (This passage appears again cited by M. Boeckh himself in his more recent dissertation ‘Untersuchungen über das kosmische System des Platon,’ p. 11). The writers named (p. 7) as having discussed the question, omitting or disregarding this most cogent argument, are names extending from Aristotle down to Ruhnken and Ideler.
It is honourable to the penetration of M. Boeckh that he should have pointed out, what so many previous critics had overlooked, that these two opinions are scientifically incompatible. He wonders, and there may be good ground for wondering, how it happened that none of these previous writers were aware of the incompatibility. But the fact that it did not occur to them, is not the less certain, and is of the greatest moment in reference to the question now under debate; for we are not now inquiring what is or is not scientifically true or consistent, but what were the opinions of Plato. M. Boeckh has called our attention to the fact, that these two opinions are incompatible; but can we safely assume that Plato must have perceived such incompatibility between them? Surely not. The Pythagoreans of his day did not perceive it; their cosmical system included both the revolution of the earth and the revolution of the sidereal sphere round the central fire, ten revolving bodies in all (Aristotel. Metaphysic. i. 35, p. 96 a. 10. De Cœlo, ii. 13, p. 293 b. 21). They were not aware that the revolutions of the one annulled those of the other as to effect, and that their system thus involved the two contradictory articles, or “mélange monstrueux,” of which Martin speaks so disdainfully. Nay, more, their opponent, Aristotle, while producing other arguments against them, never points out the contradiction. Since it did not occur to them, we can have no greater difficulty in believing that neither did it occur to Plato. Indeed, the wonder would rather be if Plato had seen an astronomical incompatibility which escaped the notice both of Aristotle and of many subsequent writers who wrote at a time when astronomical theories had been developed and compared with greater fulness. Even Ideler, a good astronomer as well as a good scholar, though he must surely have known that Plato asserted the rotation of the sidereal sphere (for no man can read the ‘Timæus’ without knowing it), ascribed to him also the other doctrine inconsistent with it, not noticing such inconsistency until M. Boeckh pointed it out.
It appears to me, therefore, that M. Boeckh has not satisfactorily made good his point — “Plato cannot have believed in the diurnal rotation of the earth, because he unquestionably believed in the rotation of the sidereal sphere as causing the succession of night and day.” For, though the two doctrines really are incompatible, yet the critics antecedent to M. Boeckh took no notice of such incompatibility. We cannot presume that Plato saw what Aristotle and other authors, even many writing under a more highly developed astronomy, did not see. We ought rather, I think, to presume the contrary, unless Plato’s words distinctly attest that he did see farther than his successors.
Now let us examine what Plato’s words do attest:— γῆν δὲ τροφὸν μὲν ἡμετέραν, εἱλλομένην (al. εἱλομένην, ἰλλομένην) δὲ περὶ τὸν διὰ παντὸς πόλον τεταμένον φύλακα καὶ δημιουργὸν νυκτός τε καὶ ἡμέρας ἐμηχανήσατο, πρώτην καὶ πρεσβυτάτην θεῶν, ὅσοι ἐντὸς οὐράνου γεγόνασι.
I explain these words as follows:—
In the passage immediately preceding, Plato had described the uniform and unchanging rotation of the outer sidereal sphere, or Circle of The Same, and the erratic movements of the sun, moon, and planets, in the interior Circles of the Diverse. He now explains the situation and functions of the earth. Being the first and most venerable of the intra-kosmic deities, the earth has the most important place in the interior of the kosmos — the centre. It is packed, fastened, or rolled, close round the axis which traverses the entire kosmos; and its function is to watch over and bring about the succession of night and day. Plato conceives the kosmic axis itself as a solid cylinder revolving or turning round, and causing thereby the revolution of the circumference or the sidereal sphere. The outer circumference of the kosmos not only revolves round its axis, but obeys a rotatory impulse emanating from its axis, like the spinning of a teetotum or the turning of a spindle. Plato in the Republic illustrates the cosmical axis by comparison with a spindle turned by Necessity, and describes it as causing by its own rotation the rotation of all the heavenly bodies (Republ. x. p. 616, c. 617 A). ἐκ δὲ τῶν ἄκρων τεταμένον Ἀνάγκης ἄτρακτον, δι’ οὗ πάσας ἐπιστρέφεσθαι τὰς περίφορας …, κυκλεῖσθαι δὲ δὴ στρεφόμενον τὸν ἄτρακτον ὅλον μὲν τὴν αὐτὴν φοραν …. στρέφεσθαι δὲ αὐτὸν ἐν τοῖς Ἀνάγκης γόνασιν.[1]
[1] Proklus in his Commentary on the Platonic Timæus (p. 682, Schn.) notes this passage of the Republic as the proper comparison from which to interpret how Plato conceived the cosmical axis. In many points he explains this correctly; but he omits to remark that the axis is expressly described as revolving, and as causing the revolution of the peripheral substance:—
—— τὸν δὲ ἄξονα μίαν θεότητα συναγωγὸν μὲν τῶν κέντρων τοῦ παντὸς συνεκτικὴν δὲ τοῦ ὅλου κόσμου, κινητικὴν δὲ τῶν θείων περιφορῶν, περὶ ἣν ἡ χορεία τῶν ὅλων, περὶ ἣν αἱ ἀνακυκλήσεις, ἀνέχουσαν τὸν ὅλον οὐρανὸν, ἣν καὶ Ἄτλαντα διὰ τοῦτο προσειρήκασιν, ὡς ἄτρεπτον καὶ ἄτρυτον ἐνέργειαν ἔχουσαν. καὶ μέντοι καὶ τὸ τεταμένον ἐνδείκνυται τιτήνιον εἶναι τὴν μίαν ταύτην δύναμιν, τὴν φρουρητικὴν τῆς ἀνακυκλήσεως τῶν ὅλων.