The Timaeus of Plato

TIMAI02. 12$
but having a contrary tendency wherefore the sun and Hermes
:
and the morning star in like manner overtake and are overtaken
one by another.
And as to the rest, were we to set forth
all the orbits wherein he put them and the causes wherefore he
did so, the account, though only by the way, would lay
on us a
heavier task than that which was our chief object in giving it.
These things perhaps may hereafter, when we have leisure, find
a fitting exposition.
five such loops are formed in eight years.
contrary motion is flagrantly inadequate
year. This process is repeated so that acquainted with Plato's astronomy), nor
to account for these facts; for since the Mercury behaves in precisely the same
motion of the planets will thus be approximately
way, except that his curve is very much
in the same direction as the more complex and the loops occur at far
motion of the Same, they would regularly shorter intervals. Now this is just what
and rapidly gain upon the sun. The truth I believe is the ivavria. dfoa.fj.is, this tendency
is, as I believe, that Plato meant the sun
on the part of Venus, as viewed
to share the contrary motion of Venus from the earth, periodically to retrace her
and Mercury in relation to the other four steps. These retrogressions of the planets
planets.
It is quite natural, seeing that were well known to the Greek astronomers,
the sun and the orbits of Venus and Mercury
who invented a complex theory of
are encircled by the orbit of the revolving spheres to account for them.
earth, while Plato supposed them all to Probably Plato meant to put forward no
revolve about the earth, that he should very definite astronomical theory : for
class them together apart from the four
whose orbits really do encircle that of the
earth : his observations would very readily
instance he gives no hint of the revolving
spheres he merely records the fact of this
:
retrogressive tendency being observable.
lead him to attributing to these three a If the contrary motion of the two
motion contrary to the rest; but there planets is insisted on, the result follows
seems nothing which could possibly have
induced him to class the sun apart from
that we have here the one theory in the
whole dialogue which is manifestly and
the two inferior planets. But if this is
flagrantly inadequate. Plato's physical
so, what is the tvavria. 8'jva.fus? What I theories, however far they may differ
believe it to be may be understood from
accompanying figure, which is copied
from the conclusions of modern science,
usually offer a fair and reasonable explanation
from part of a diagram in Arago's
of such facts as were known to
Popular Astronomy. This represents the him: they are sometimes singularly felicitous,
motion of Venus relative to the earth
and never absurd. I cannot then
during one year, as observed in 1713. believe that he has here presented us
It will be seen that the planet pursues her with a hypothesis so obviously futile.
path among the stars pretty steadily from And if he had, how did it
escape the
January to May; after that she wavers, vigilance of Aristotle, who would have
begins a retrograde movement, and then been ready enough to seize the occasion
once more resumes her old course, thus of making a telling point against Plato ?
forming a loop, which is traversed from It is remarkable that neither in Republic
May to August. After that she proceeds
617 A, nor in Epinomis 986 E (the
unfaltering on her way for the rest of the author of which must have been well