Part 1

PLATO'S DOCTRINE

RESPECTING THE

ROTATION OF THE EARTH,

AND

ARISTOTLE'S COMMENT UPON THAT DOCTRINE.

BY GEORGE GROTE, ESQ.

LONDON: JOHN MURRAY, ALBEMARLE STREET. 1860.

_The right of Translation is reserved._

LONDON: PRINTED BY WILLIAM CLOWES AND SONS, STAMFORD STREET, AND CHARING CROSS.

EXAMINATION OF THE THREE FOLLOWING QUESTIONS:--

1. WHETHER THE DOCTRINE OF THE EARTH'S ROTATION IS AFFIRMED OR IMPLIED IN THE PLATONIC TIMÆUS?

2. IF AFFIRMED OR IMPLIED, IN WHAT SENSE?

3. WHAT IS THE COSMICAL FUNCTION WHICH PLATO ASSIGNS TO THE EARTH IN THE TIMÆUS?

PREFACE.

The following paper was originally intended as an explanatory note on the Platonic Timæus, in the work which I am now preparing on Plato and Aristotle. Interpreting, differently from others, the much debated passage in which Plato describes the cosmical function of the Earth, I found it indispensable to give my reasons for this new view. But I soon discovered that those reasons could not be comprised within the limits of a note. Accordingly I here publish them in a separate Dissertation. The manner in which the Earth's rotation was conceived, illustrates the scientific character of the Platonic and Aristotelian age, as contrasted with the subsequent development and improvement of astronomy.

PLATO--ON THE EARTH'S ROTATION.

In Plato, Timæus, p. 40 B, we read the following words--[Greek: Gê=n de\ tropho\n me\n ê(mete/ran, ei(llome/nên de\ peri\ to\n dia\ panto\s po/lon tetame/non phu/laka kai\ dêmiourgo\n nukto/s te kai\ ê(me/ras e)mêchanê/sato, prô/tên kai\ presbuta/tên theô=n, o(/soi e)nto\s ou)ra/nou gego/nasi.] I give the text as it stands in Stallbaum's edition.

The obscurity of this passage is amply attested by the numerous differences of opinion to which it has given rise, both in ancient and in modern times. Various contemporaries of Plato ([Greek: e)/nioi]--Aristot. De Coelo, II. 13, p. 293 b. 30) understood it as asserting or implying the rotatory movement of the earth in the centre of the Kosmos, and adhered to this doctrine as their own. Aristotle himself alludes to these contemporaries without naming them, and adopts their interpretation of the passage; but dissents from the doctrine, and proceeds to impugn it by arguments. Cicero mentions (Academic II. 39) that there were persons who believed Plato to have indicated the same doctrine obscurely, in his Timaeus: this passage must undoubtedly be meant. Plutarch devotes a critical chapter to the enquiry, what was Plato's real doctrine as to the cosmical function of the earth--its movement or rest (Quaestion. Platonic. VII. 3, p. 1006.)

There exists a treatise, in Doric dialect, entitled [Greek: Ti/maio** tô= Lo/krô Peri\ Psucha=s Ko/smô kai\ Phu/sios], which is usually published along with the works of Plato. This treatise was supposed in ancient times to be a genuine production of the Lokrian Timaeus, whom Plato introduces as his spokesman in the dialogue so called. As such, it was considered to be of much authority in settling questions of interpretation as to the Platonic Timaeus. But modern critics hold, I believe unanimously, that it is the work of some later Pythagorean or Platonist, excerpted or copied from the Platonic Timaeus. This treatise represents the earth as being in the centre and at rest. But its language, besides being dark and metaphorical, departs widely from the phraseology of the Platonic Timaeus: especially in this--that it makes no mention of the cosmical axis, nor of the word [Greek: i)llome/nên] or [Greek: ei(loume/nên].

Alexander of Aphrodisias (as we learn from Simplikius ad Aristot. De Coelo, fol. 126) followed the construction of Plato given by Aristotle. "It was improbable (he said) that Aristotle could be ignorant either what the word signified, or what was Plato's purpose" ([Greek: a)lla\ tô=| A)ristote/lei, phêsi\n, ou(/tô le/gonti _i)/llesthai_, ou)k eu)/logon a)ntile/gein; ô(s a)lêthô=s ga\r ou)/te tê=s le/xeôs to\ sêmaino/menon ei)ko\s ê)=n a)gnoei=n au)to\n, ou)/te to\n Pla/tônos skopo/n.] This passage is not given in the Scholia of Brandis). Alexander therefore construed [Greek: i)llome/nên] as meaning or implying rotatory movement, though in so doing he perverted (so Simplikius says) the true meaning to make it consonant with his own suppositions.

Proklus maintains that Aristotle has interpreted the passage erroneously,--that [Greek: i)llome/nên] is equivalent to [Greek: sphiggome/nên] or [Greek: xunechome/nên]--and that Plato intends by it to affirm the earth as at rest in the centre of the Kosmos (ad Timaeum, Book iv., p. 681 ed. Schneider). Simplikius himself is greatly perplexed, and scarcely ventures to give a positive opinion of his own. On the whole, he inclines to believe that [Greek: i)llome/nên] might possibly be understood, by superficial readers, so as to signify rotation, though such is not its proper and natural sense: that some Platonists did so misunderstand it: and that Aristotle accepted their sense for the sake of the argument, without intending himself to countenance it (ad Aristot. De Coelo, p. 126).

Both Proklus and Simplikius, we must recollect, believed in the genuineness of the Doric treatise ascribed to Timaeus Locrus. Reasoning upon this basis, they of course saw, that if Aristotle had correctly interpreted Plato, Plato himself must have interpreted _incorrectly_ the doctrine of Timaeus. They had to ascribe wrong construction either to Plato or to Aristotle: and they could not bear to ascribe it to Plato.

Alkinous, in his Eisagôge (c. 15) gives the same interpretation as Proklus. But it is remarkable that in his paraphrase of the Platonic words, he calls the earth [Greek: ê(me/ras phu/lax kai\ nukto/s]: omitting the significant epithet [Greek: dêmiourgo/s].

In regard to modern comments upon the same disputed point, I need only mention (besides those of M. Cousin, in the notes upon his translation of the 'Timæus', and of Martin in his 'Études sur le Timée') the elaborate discussion which it has received in the two recent Dissertations 'Ueber die kosmischen Systeme der Griechen,' by Gruppe and Boeckh. Gruppe has endeavoured, upon the evidence of this passage, supported by other collateral proofs, to show that Plato, towards the close of his life, arrived at a belief, first, in the rotation of the earth round its own axis, next, at the double movement of the earth, both rotation and translation, round the sun as a centre (that is, the heliocentric or Copernican system): that Plato was the first to make this discovery, but that he was compelled to announce it in terms intentionally equivocal and obscure, for fear of offending the religious sentiments of his contemporaries ('Die kosmischen Systeme der Griechen, von O. F. Gruppe,' Berlin, 1851). To this dissertation M. Boeckh--the oldest as well as the ablest of all living philologists--has composed an elaborate reply, with his usual fulness of illustrative matter and sobriety of inference. Opinions previously delivered by him (in his early treatises on the Platonic and Pythagoreian philosophy) had been called in question by Gruppe: he has now re-asserted them and defended them at length, maintaining that Plato always held the earth to be stationary and the sidereal sphere rotatory--and answering or extenuating the arguments which point to an opposite conclusion ('Untersuchungen über das kosmische System des Platon, von August Boeckh,' Berlin, 1852).

Gruppe has failed in his purpose of proving that Plato adopted either of the two above-mentioned doctrines--either the rotation of the earth round its own axis, or the translation of the earth round the sun as a centre. On both these points I concur with Boeckh in the negative view. But though I go along with his reply as to its negative results, I cannot think it satisfactory in its positive aspect as an exposition of the doctrine proclaimed in the Platonic Timæus: nor can I admit that the main argument of M. Boeckh's treatise is sufficient to support the inference which he rests upon it. Moreover, he appears to me to set aside or explain away too lightly the authority of Aristotle. I agree with Alexander of Aphrodisias and with Gruppe who follows him, in pronouncing Aristotle to be a good witness, when he declares what were the doctrines proclaimed in the Platonic Timæus; though I think that Gruppe has not accurately interpreted either Timæus or Aristotle.

The capital argument of Boeckh is as follows: "The Platonic Timæus affirms, in express and unequivocal terms, the rotation of the outer celestial sphere (the sidereal sphere or Aplanes) in twenty-four hours, as bringing about and determining the succession of day and night. Whoever believes this cannot at the same time believe that the earth revolves round its own axis in twenty-four hours, and that the succession of day and night is determined thereby. The one of these two affirmations excludes the other; and, as the first of the two is proclaimed, beyond all possibility of doubt, in the Platonic Timæus, so we may be sure that the second of the two cannot be proclaimed in that same discourse. If any passage therein seems to countenance it, we must look for some other mode of interpreting the passage."

This is the main argument of M. Boeckh, and also of Messrs. Cousin and Martin. The latter protests against the idea of imputing to Plato "un mélange monstrueux de deux systêmes incompatibles" (Études sur le Timée, vol. ii. p. 86-88).

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 Coelo, 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 Coelestium 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 [Greek: a)planê=] 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 Coelo, 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:--[Greek: gê=n de\ tropho\n me\n ê(mete/ran, ei(llome/nên] (al. [Greek: ei(lome/nên, i)llome/nên]) [Greek: de\ peri\ to\n dia\ panto\s po/lon tetame/non phu/laka kai\ dêmiourgo\n nukto/s te kai\ ê(me/ras e)mêchanê/sato, prô/tên kai\ presbuta/tên theô=n, o(/soi e)nto\s ou)ra/nou gego/nasi.]

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). [Greek: e)k de\ tô=n a)/krôn tetame/non A)na/gkês a)/trakton, di' ou(= pa/sas e)pistre/phesthai ta\s peri/phoras . . . , kuklei=sthai de\ dê\ strepho/menon to\n a)/trakton o(/lon me\n tê\n au)tê\n phoran . . . . stre/phesthai de\ au)to\n e)n toi=s A)na/gkês go/nasin.][1]

[Footnote 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:--

----[Greek: to\n de\ a)/xona mi/an theo/têta sunagôgo\n me\n tô=n ke/ntrôn tou= panto\s sunektikê\n de\ tou= o(/lou ko/smou, _kinêtikê\n de\ tô=n thei/ôn periphorô=n_, peri\ ê(\n ê( chorei/a** tô=n o(/lôn, peri\ ê(\n ai( a)nakuklê/seis, a)ne/chousan to\n o(/lon ou)rano\n,** ê(\n kai\ A)/tlanta dia\ tou=to proseirê/kasin, ô(s a)/trepton kai\ a)/truton e)ne/rgeian e)/chousan. kai\ me/ntoi kai\ to\ tetame/non** e)ndei/knutai** titê/nion ei)=nai tê\n mi/an _tau/tên du/namin, tê\n phrourêtikê\n tê=s a)nakuklê/seôs tô=n o(/lôn_.]

Here Proklus recognises the efficacy of the axis in producing and maintaining the revolution of the Kosmos, but he does not remark that it initiates this movement by revolving itself. The [Greek: Theotê\s], which Proklus ascribes to the axis, is invested in the earth packed round it, by the Platonic Timæus.]

Now the function which Plato ascribes to the earth in the passage of the Timæus before us is very analogous to that which in the Republic he ascribes to Necessity--the active guardianship of the axis of the kosmos and the maintenance of its regular rotation. With a view to the exercise of this function, the earth is planted in the centre of the axis, the very root of the kosmic soul (Plato, Timæus, p. 34 B). It is even "packed close round the axis," in order to make sure that the axis shall not be displaced from its proper situation and direction. The earth is thus not merely active and influential, but is really the chief regulator of the march of the kosmos, being the immediate neighbour and auxiliary of the kosmic soul. Such a function is worthy of "the first and eldest of intra-kosmic deities," as Plato calls the earth. With perfect propriety he may say that the earth, in the exercise of such a function, "is guardian and artificer of day and night." This is noway inconsistent with that which he says in another passage, that the revolutions of the outer sidereal sphere determine day and night. For these revolutions of the outer sidereal sphere depend upon the revolutions of the axis, which latter is kept in uniform position and movement by the earth grasping it round its centre and revolving with it. The earth does not determine days and nights by means of its own rotations, but by its continued influence upon the rotations of the kosmic axis, and (through this latter) upon those of the outer sidereal sphere.

It is important to attend to the circumstance last mentioned, and to understand in what sense Plato admitted a rotatory movement of the earth. In my judgment, the conception respecting the earth and its functions, as developed in the Platonic Timæus, has not been considered with all its points taken together. One point among several, and that too the least important point, has been discussed as if it were the whole, because it falls in with the discussions of subsequent astronomy. Thus Plato admits the rotation of the earth, but he does not admit it as producing any effects, or as the primary function of the earth: it is only an indirect consequence of the position which the earth occupies in the discharge of its primary function--of keeping the cosmical axis steady, and maintaining the uniformity of its rotations. If the cosmical axis is to revolve, the earth, being closely packed and fastened round it, must revolve along with it. If the earth stood still, and resisted all rotation of its own, it would at the same time arrest the rotations of the cosmical axis, and of course those of the entire kosmos besides.

The above is the interpretation which I propose of the passage in the Platonic Timæus, and which I shall show to coincide with Aristotle's comment upon it. Messrs. Boeckh and Martin interpret differently. They do not advert to the sense in which Plato conceives the axis of the kosmos--not as an imaginary line, but as a solid revolving cylinder; and moreover they understand the function assigned by the Platonic Timæus to the earth in a way which I cannot admit. They suppose that the function assigned to the earth is not to keep up and regularize, but to withstand and countervail, the rotation of the kosmos. M. Boeckh comments upon Gruppe, who had said (after Ideler) that when the earth is called [Greek: phu/laka _kai\ dêmiourgo\n_ nukto\s kai\ ê(me/ras], Plato must have meant to designate some active function ascribed to it, and not any function merely passive or negative. I agree with Gruppe in this remark, and I have endeavoured to point out what this active function of the earth is, in the Platonic theory. But M. Boeckh (Untersuchungen, &c., p. 69-70) controverts Gruppe's remark, observing, first, that it is enough if the earth is in any way necessary to the production of the given effect; secondly, that if active force be required, the earth (in the Platonic theory) does exercise such, by its purely passive resistance, which is in itself an energetic putting forth of power.