The revolution of the world around earth, which is accomplished in a single
day and night, is described as being the most perfect or intelligent. Yet
Plato also speaks of an 'annus magnus' or cyclical year, in which periods
wonderful for their complexity are found to coincide in a perfect number,
i.e. a number which equals the sum of its factors, as 6 = 1 + 2 + 3. This,
although not literally contradictory, is in spirit irreconcilable with the
perfect revolution of twenty-four hours. The same remark may be applied to
the complexity of the appearances and occultations of the stars, which, if
the outer heaven is supposed to be moving around the centre once in twenty-
four hours, must be confined to the effects produced by the seven planets.
Plato seems to confuse the actual observation of the heavens with his
desire to find in them mathematical perfection. The same spirit is carried
yet further by him in the passage already quoted from the Laws, in which he
affirms their wanderings to be an appearance only, which a little knowledge
of mathematics would enable men to correct.

We have now to consider the much discussed question of the rotation or
immobility of the earth. Plato's doctrine on this subject is contained in
the following words:--'The earth, which is our nurse, compacted (OR
revolving) around the pole which is extended through the universe, he made
to be the guardian and artificer of night and day, first and eldest of gods
that are in the interior of heaven'. There is an unfortunate doubt in this
passage (1) about the meaning of the word (Greek), which is translated
either 'compacted' or 'revolving,' and is equally capable of both
explanations. A doubt (2) may also be raised as to whether the words
'artificer of day and night' are consistent with the mere passive causation
of them, produced by the immobility of the earth in the midst of the
circling universe. We must admit, further, (3) that Aristotle attributed
to Plato the doctrine of the rotation of the earth on its axis. On the
other hand it has been urged that if the earth goes round with the outer