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

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PHYSICS 489
greater gravity, sink downward ; so the former fill the
upper, the latter the lower, region of the atmosphere. 1
The spherical form of the lower world involves that
of the celestial
touches it at all points. 2
region which surrounds the former and
But considered in themselves,
the heavens could scarcely be supposed to have another
shape, 3 since the sphere is the first and most perfect
figure, and therefore the one appropriate to the first
body. Moreover, it is only this figure which can
revolve within the space which it encloses, 4 and external
to the heavens there is no space. Lastly, the
motion of the heavens, being the measure of all movement,
must be the most rapid ;
but the most rapid is
that which has the shortest journey, and a circle is the
shortest road from the same point to the same point. 5
1
Meteor, i. 3, 340, b, 19 sqq.
341, a, 2, c. 4, 341, b, 6-22; of.i.
7, 344, b, 8, c 8, 345, b, 32 ; ii. 2,
354, b, 4 sqq. ; Be Ccelo, ii. 4,
287, a,, 30 ; on the difference between
dry and moist vapours
[ava.Bvp.iaa'is, or Kairvbs and arfils),
v. also Meteor, ii. 4, 359, b, 28,
360, a, 31, iii. 6. 378, a, 18.
2
Be Ccelo, ii. 4, 287, a, 30
sqq. As there can be no space
which is void (see pp. 432 sq.),
it follows that the celestial and
the fiery spheres are at all points
in contact with one another.
a
For what follows see Be
Coelo, ii. 4.
1
Ibid. 287, a, 11. This statement
is certainly strange, for as
Alex, apud Simpl. in, loeo,
ScJiol. 493, b, 22, observed at an
early date, a whole series of
figures share this attribute
with the sphere, viz. all those
which are described by the
spinning of a smooth body, and
of which, therefore, each section
which cuts the axis at right
angles forms a circle whose
centre is on the line of the axis.
Simplicius gets out of the difficulty
by remarking that, while
in the case of other shapes there
is only one axis that will serve
the purpose, in a sphere you
may take any you please ; an explanation
with which we may
rest content on so trifling a point.
5
Or as Simplicius, in loco,
explains it: of all lines which
return to the point from which
they started, and thus inclose a
space, the circle is the shortest
just as of all surfaces of equal
extent that which is circular, of
all bodies of equal bulk that
which is globular, has the smallest
circumference. Even with this
490 ARISTOTLE
The finer and more uniform its matter is, the more
perfectly spherical will be the shape of the celestial
world
l
as, indeed, in the most perfect body matter
must be perfectly adapted to its form, and as the arguments
by which the spherical shape of heaven is proved 2
require. Still we cannot regard the matter of the
heavens as uniformly homogeneous. Nature, in Aristotle's
opinion, reconciles all opposites by a gradual
process, and the piirity of the sether, which composes
heaven, diminishes as it approaches the terrestrial
atmosphere. 3
In proceeding to investigate the disposition of the
heavens, Aristotle is guided by observation. 4 All the
explanation the argument is a
lame one. It is obvious that
Aristotle accepts the globular
form of the earth on the direct
evidence of the senses, and
merely adds these other proofs
as supplementary evidence.
1
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