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
[Greek: ei(lome/nên] or [Greek: i)llome/nên] has no distinct
meaning at all, if it does not mean this. The very synonyms
([Greek: sphiggome/nên, peridedeme/nên], &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.
We must remember that Plato had been actually present at the trial
of Sokrates. He had heard the stress laid by the accusers on
astronomical heresies, analogous to those of Anaxagoras, which
they imputed to Sokrates--and the pains taken by the latter to
deny that he held such opinions (see the Platonic Apology). The
impression left by such a scene on Plato's mind was not likely to
pass away: nor can we be surprised that he preferred to use
propositions which involved and implied, rather than those which
directly and undisguisedly asserted, the heretical doctrine of the
earth's rotation. That his phraseology, however indirect, was
perfectly understood by contemporary philosophers, both assentient
and dissentient, as embodying his belief in the doctrine--is
attested by the two passages of Aristotle.
Upon these reasons alone I should dissent from M. Cousin's sixth
argument. But I have other reasons besides. He rests it upon the
two allegations that the doctrine of the earth's motion was the
subject of much controversial debate in Plato's time, and of great
importance in itself. Now the first of these two allegations can
hardly be proved, as to the time of Plato; for Aristotle, when he
is maintaining the earth's immobility, does not specify any other
opponents than the Pythagoreians and the followers of the Platonic
Timæus. And the second allegation I believe to be unfounded,
speaking with reference to the Platonic Timæus. In the cosmical
system therein embodied, the rotation of the earth round the
cosmical axis, though a real part of the system, was in itself a
fact of no importance, and determining no results. The capital
fact of the system was the position and function of the earth,
packed close round the centre of the cosmical axis, and regulating
the revolutions of that axis. Plato had no motive to bring
prominently forward the circumstance that the earth revolved
itself along with the cosmical axis, which circumstance was only
an incidental accompaniment.
I have thus examined all the arguments adduced by M. Cousin,
and have endeavoured to show that they fail in establishing his
conclusion. There is, however, one point of the controversy in
which I concur with him more than with Boeckh and Martin. This
point is the proper conception of what Plato means by the
_cosmical axis_. Boeckh and Martin seem to assume this upon
the analogy of what is now spoken of as the axis of the earth: M.
Boeckh (p. 13) declares the axis of the kosmos to be a
prolongation of that axis. But it appears to me (and M. Cousin's
language indicates the same) that Plato's conception was something
very different. The axis of the earth (what astronomers speak of
as such) is an imaginary line traversing the centre of the earth;
a line round which the earth revolves. Now the cosmical axis, as
Plato conceives it, is a solid material cylinder, which not only
itself revolves, but causes by this revolution the revolution of
the exterior circumference of the kosmos. This is a conception
entirely different from that which we mean when we speak of the
axis of the earth. It is, however, a conception symbolically
enunciated in the tenth book of the Republic, where the spindle of
Necessity is said to be composed of adamant, hard and solid
material, and to cause by its own rotation the rotation of all the
_verticilli_ packed and fastened around it. What is thus
enunciated in the Republic is implied in the Timæus. For when we
read therein that the earth is packed or fastened round the
cosmical axis, how can we understand it to be packed or fastened
round an imaginary line? I will add that the very same meaning is
brought out in the translation of Cicero--"_trajecto axe
sustinetur_" (terra). The axis, round which the earth is
fastened, and which sustains the earth, must be conceived, not as
an imaginary line, but as a solid cylinder, itself revolving;
while the earth, being fastened round it, revolves round and along
with it. The axis, in the sense of an imaginary line, cannot be
found in the conception of Plato.
Those contemporaries of Plato and Aristotle, who all agreed in
asserting the revolution of the celestial sphere, did not all
agree in their idea of the force whereby such revolution was
brought about. Some thought that the poles of the celestial sphere
exercised a determining force: others symbolised the mythical
Atlas, as an axis traversing the sphere from pole to pole and
turning it round. (Aristotel. De Motu Animal. 3. p. 699 a. 15-30.)
Aristotle himself advocated the theory of a _primum movens
immobile_ acting upon the sphere from without the sphere. Even
in the succeeding centuries, when astronomy was more developed,
Aratus, Eratosthenes, and their commentators, differed in
their way of conceiving the cosmical axis. Most of them considered
it as solid: but of these, some thought it was stationary, with
the sphere revolving round it--others that it revolved itself:
again, among these latter, some believed that the revolutions of
the axis determined those of the surrounding sphere--others, that
the revolutions of the sphere caused those of the axis within it.
Again, there were some physical philosophers who looked at the
axis as airy or spiritual--[Greek: to\ dia\ me/sou tê=s sphai/ras
diê=kon pneu=ma]. Then there were geometers who conceived it only
as an imaginary line. (See the Phaenomena of Aratus 20-25--with
the Scholia thereon; Achilles Tatius ad Arati Phaenom. apud
Petavium--Uranolog. p. 88; also Hipparchus ad Arat. ib. p. 144.) I
do not go into these dissentient opinions farther than to show,
how indispensable it is, when we construe the passage in the
Platonic Timaeus, [Greek: peri\ to\n dia\ panto\s po/lon
tetame/non], to enquire in what sense Plato understood the
cosmical axis: and how unsafe it is to assume at once that he must
have conceived it as an imaginary line.
Proklus argues that because the earth is mentioned by Plato in the
Phædon as stationary in the centre of the heaven, we cannot
imagine Plato to affirm its rotation in the Timæus. I agree with
M. Boeckh in thinking this argument inconclusive; all the more,
because, in the Phædon, not a word is said either about the axis
of the kosmos, or about the rotation of the kosmos; all that
Sokrates professes to give is [Greek: tê\n i)de/an tê=s gê=s kai\
tou\s to/pous au)tê=s**] (p. 108 E). No cosmical system or theory
is propounded in that dialogue.
When we turn to the Phædrus, we find that, in its highly poetical
description, the rotation of the heaven occupies a prominent
place. The internal circumference of the heavenly sphere, as well
as its external circumference or back ([Greek: nô=ton]), are
mentioned; also its periodical rotations, during which the gods
are carried round on the back of the heaven, and contemplate the
eternal Ideas occupying the super-celestial space (p. 247, 248),
or the plain of truth.[5] But the purpose of this poetical
representation appears to be metaphysical and intellectual, to
illustrate the antithesis presented by the world of Ideas and
Truth on one side--against that of sense and appearances on the
other. Astronomically and cosmically considered, no
intelligible meaning is conveyed. Nor can we even determine
whether the rotations of the heaven, alluded to in the Phædrus,
are intended to be diurnal or not; I incline to believe not
([Greek: me/chri tê=s _e(te/ras_ perio/dou]--p. 248--which
can hardly be understood of so short a time as one day). Lastly,
nothing is said in the Phædrus about the cosmical axis; and it is
upon this that the rotations of the earth intimated in the Timæus
depend.
[Footnote 5: Whether [Greek: E)sti/a] in the Phædrus, which is
said "to remain alone stationary in the house of the Gods," can be
held to mean the Earth, is considered by Proklus to be uncertain
(p. 681).]
Among the different illustrations, given by Plato in his different
dialogues respecting the terrestrial and celestial bodies, I
select the tenth book of the Republic as that which is most
suitable for comparison with the Timæus, because it is only
therein that we learn how Plato conceived the axis of the kosmos.
M. Boeckh (Untersuchungen, p. 86) wishes us to regard the
difference between the view taken in the Phædon, and that in the
Republic, as no way important; he affirms that the adamantine
spindle in the Republic is altogether mythical or poetical, and
that Plato conceives the axis as not being material. On this point
I dissent from M. Boeckh. The mythical illustrations in the tenth
book of the Republic appear to me quite unsuitable to the theory
of an imaginary, stationary, and immaterial axis. Here I much more
agree with Gruppe (p. 15, 26-29), who recognises the solid
material axis as an essential feature of the cosmical theory in
the Republic; and recognises also the marked difference between
that theory and what we read in the Phædon. Yet, though Gruppe is
aware of this important difference between the Republic and the
Phædon, he still wishes to illustrate the Timæus by the latter and
not by the former. He affirms that the earth in the Timæus is
conceived as unattached, and freely suspended, the same as in the
Phædon; but that in the Timæus it is conceived, besides, as
revolving on its own axis, which we do not find in the Phædon (p.
28, 29). Here I think Gruppe is mistaken. In construing the words
of Timæus, [Greek: ei(lome/nên (i)llome/nên) peri\ to\n dia\
panto\s po/lon tetame/non], as designating "the unattached earth
revolving round its own axis," he does violence not less to the
text of Plato than to the expository comment of Aristotle. Neither
in the one nor the other is anything said about _an axis of the
earth_; in both, the cosmical axis is expressly designated;
and, if Gruppe is right in his interpretation of [Greek:
ei(lome/nên], we must take Plato as affirming, not that the earth
is fastened round the cosmical axis, but that it revolves, though
unattached, around that axis, which is a proposition both
difficult to understand, and leading to none of those astronomical
consequences with which Gruppe would connect it. Again, when
Gruppe says that [Greek: ei(lome/nên peri\] does _not_ mean
_packed or fastened round_, but that it _does_ mean
_revolving round_, he has both the analogies of the word and
the other commentators against him. The main proof, if not the
only proof, which he brings, is that Aristotle so construed it.
Upon this point I join issue with him. I maintain that Aristotle
does _not_ understand [Greek: ei(lome/nên] or [Greek:
i)llome/nên peri\] as naturally meaning _revolving round_,
and that he does understand the phrase as meaning _fastened
round_. When we find him, in the second passage of the treatise
De Coelo, not satisfied with the verb [Greek: i)/llesthai]
alone, but adding to it the second verb [Greek: _kai\
kinei=sthai_], we may be sure that he did not consider [Greek:
i)/llesthai] as naturally and properly denoting _to revolve_
or _move round_.
Agreeing as I do with Gruppe in his view, that the interpretation
put by Aristotle is the best evidence which we can follow in
determining the meaning of this passage in the Timæus, I contend
that the authority of Aristotle contradicts instead of justifying
the conclusion at which he arrives. Aristotle understands [Greek:
i)llome/nên] as meaning _packed or fastened round_; he does
not understand it as meaning, when taken by itself, _revolving
round_.
The two meanings here indicated are undoubtedly distinct and
independent. But they are not for that reason contradictory and
incompatible. It has been the mistake of critics to conceive them
as thus incompatible; so that if one of the two were admitted, the
other must be rejected. I have endeavoured to show that this is
not universally true, and that there are certain circumstances in
which the two meanings not only may come together, but must come
together. Such is the case when we revert to Plato's conception of
the cosmical axis as a solid revolving cylinder. That which is
packed or fastened around the cylinder must revolve around it, and
along with it.
Both M. Boeckh and Gruppe assume the incompatibility of the two
meanings; and we find the same assumption in Plutarch's criticisms
on the Timæus (Plutarch. Quæst. Platon. p. 1006 C), where he
discusses what Plato means by [Greek: o)/rgana chro/nou]; and in
what sense the earth as well as the moon can be reckoned as
[Greek: o)/rganon chro/nou] (Timæus, p. 41 E, 42 D). Plutarch
inquires how it is possible that the earth, if stationary and at
rest, can be characterised as "among the instruments of time;" and
he explains it by saying that this is true in the same sense as we
call a gnomon or sun-dial an instrument of time, because, though
itself never moves, it marks the successive movements of the
shadow. This explanation might be admissible for the phrase
[Greek: o)/rganon chro/nou]; but I cannot think that the
immobility of the earth can be made compatible with the attribute
which Plato bestows upon it of being [Greek: phu/lax kai\
_dêmiourgo\s_ nukto\s te kai\ ê(me/ras].
The difficulty, however, vanishes when we understand the function
ascribed by Plato to the earth as I have endeavoured to elucidate
it. The earth not only is not at rest, but cannot be at rest,
precisely because it is packed round the solid revolving cosmical
axis, and must revolve along with it. The function of the earth,
as the first and oldest of intra-kosmic deities, is to uphold and
regulate the revolutions of this axis, upon which depend the
revolutions of the sidereal sphere or outer shell of the kosmos.
It is by virtue of this regulating function (and not by virtue of
its rotation) that the earth is the guardian and artificer of
night and day. It is not only "an instrument of time," but the
most potent and commanding among all instruments of time.
What has just been stated is, in my belief, the theory of the
Platonic Timæus, signified in the words of that dialogue, and
embodied in the comment of Aristotle. The commentators, subsequent
to Aristotle, so far as we know them, understood the theory in a
sense different from what Plato intended. I think we may see how
this misconception arose. It arose from the great development and
elaboration of astronomical theory during the two or three
generations immediately succeeding Plato. Much was added by
Eudoxus and others, in their theory of concentric spheres: more
still by others of whom we read in Cicero (Academ. II. 39.)
"Hicetas Syracusius, ut ait Theophrastus, coelum, solem, lunam,
stellas, supera denique omnia, stare censet, neque praeter terram
rem ullam in mundo moveri: quae cum circum axem se summâ
celeritate convertat et torqueat, eadem effici omnia, quae si
stante terrâ coelum moveretur. Atque hoc etiam Platonem in Timaeo
dicere quidam arbitrantur, sed paullo obscurius." The same
doctrine is said to have been held by Herakleides of Pontus, the
contemporary of Aristotle, and by others along with him.
(Simplikius ad Aristot. Physic. p. 64--De Coelo, p. 132--Plutarch.
Plac. Phil. III. 13.) The doctrine of the rotation of the Earth
here appears along with another doctrine--the immobility of the
sidereal sphere and of the celestial bodies. The two are presented
together, as correlative portions of one and the same astronomical
theory. There are no celestial revolutions, and therefore there is
no solid celestial axis. Moreover, even Aristarchus of Samos (who
attained to a theory substantially the same as the Copernican,
with the double movement of the Earth, rotation round its own
axis, and translation round the sun as a centre) comes within less
than a century after Plato's death.
Though the _quidam_ alluded to by Cicero looked upon the
obscure sentence in Plato's Timaeus as a dim indication of the
theory of Hicetas, yet the two agree only in the supposition of a
rotation of the earth, and differ essentially in the pervading
cosmical conceptions. Hicetas states distinctly that which his
theory denies, as well as that which it affirms. The negation of
the celestial rotations, is in his theory a point of capital and
coordinate importance, on which he contradicts both Plato and
Aristotle as well as the apparent evidence of sense. I cannot
suppose that this theory can have been proclaimed or known to
Aristotle when his works were composed: for the celestial
revolutions are the keystone of his system, and he could hardly
have abstained from combating a doctrine which denied them
altogether. In the hands of Hicetas (perhaps in those of
Herakleides, if we may believe what is said about him) astronomy
appears treated as a science by itself, with a view "to provide
such hypotheses as may save the phenomena" ([Greek: sô/zein ta\
phaino/mena], Simpl. ad Aristot. De Coelo, p. 498, Schol.
Brandis). It becomes detached from those religious, ethical,
poetical, teleological, arithmetical decrees or fancies, in which
we see it immersed in the Platonic Timaeus, and even (though
somewhat less) in the Aristotelian Treatise De Coelo. Hence the
meaning of Plato, obscurely announced from the beginning, ceased
to be understood: the solid revolving axis of the Kosmos, assumed
without being expressly affirmed in his Timaeus, dropped out of
sight: the doctrine of the rotation of the earth was presented in
a new point of view, as a substitute for the celestial
revolutions. But no proper note was taken of this transition. The
doctrine of Plato was assumed to be the same as that of Hicetas.
When we read Plutarch's criticism (Quæst. Plat. p. 1006 C) upon
the word [Greek: i)llome/nên], we see that he puts to himself the
question thus--"Does Plato in the Timæus conceive the earth as
kept together and stationary--or as turning round and revolving,
agreeably to the subsequent theory of Aristarchus and Seleukus?"
Here we find that Plutarch conceives the alternative thus--Either
the earth does not revolve at all, or it revolves as Aristarchus
understood it. One or other of these two positions must have been
laid down by Plato in the Timæus.--So we read in Plutarch. But the
fact is, that Plato meant neither the one nor the other. The
rotation of the earth round the solid cosmical axis, which he
affirms in the Timæus--is a phenomenon utterly different from
the rotation of the earth as a free body round the imaginary line
called its own axis, which was the doctrine of Aristarchus.