ARISTOTLE AND THE EARLIER PERIPATETICS vol.I by Eduard Zeller, B.F.C.Costelloe 1897

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PHYSICS
Mara, Venus, Mercury, and the sun ;
giving in all
fifty-five or, if we add in the sphere of fixed stars,
fifty-six spheres, together with as many eternal incorporeal
unmoved entities from whom the motions of the
spheres proceed. 1 The progress of observation could
tAM
not fail to show that the theory of spheres, even as thus
conceived, was inadequate to explain the phenomena
accordingly, as early as the middle of the third century
before Christ, Apollonius of Perga advanced his theory of
' epicycles ' triumphantly against it. 2 Yet even the antagonists
of Aristotle's system admitted that his theory
of retrogressive spheres was an ingenious attempt to
rectify and supplement the hypothesis of Eudoxus. 3
1
Metaph. ibid. cf. Simpl.
ibid. 500, a, 34 sqq. ; Krische,
iMd. 206 sqq. ; Idblee, ibid. 82
BONlTzand Schwegler on the
passage in the Metaphysics.
There Ariototle expressly says,
1. 17 sqq., that more spheres are
not required, for, since every
motion exists for the sake of
that which is moved, there can
be no motion and therefore no
sphere in the heavens which is
not there for the
sake of a star.
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