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

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PHYSICS 429
either move in a circle like the celestial spheres or in
straight lines up and down like the elemental bodies,
infinity admits of neither of these movements. The
former is impossible, because circles are by their nature
circumscribed, and circular movement is rotation round
a centre, whereas in the infinite there is no centre ; ' the
latter, because lineal motion has a starting point and
end. 2 Indeed, ' infinity ' could not move at all, since it
would take infinite time to traverse the smallest conceivable
space. 3 Finally, Aristotle uses an argument
conclusive with Greeks, who could not imagine formless
being : the infinite, as such, is incomplete and without
shape—we call that infinite the magnitude of which is
indeterminable, which is never finished and complete,
which cannot be limited
in such a way as not to leave
some portion of it outside. 4 The infinite first becomes
a whole and complete when it is enclosed by means of
form. But the world cannot be conceived except as
complete and a whole. 5 It is therefore impossible that
init. u. 7, 274, b, 8, 29. 276, b, 6
sqq. In c. 6, 273, a, 21 sqq., the
same conclusion is reached by
showing that infinite bodif "tup t
be infinitely heavy or light," *>ut
an infinitely heavy or an infinitely
light body is an impossibility,
since it must either exhibit
infinite speed or be absolutely
immovable.
1
As is shown, at unnecessary
length, De Coelo, i. 5, 271, b, 2ri
sqq. 272, b, 17 sqq. c. 7, 275, b,
12.
2
De Coelo, i. 6 mit. Also c. 7,
275, b, 15 sqq.
3 Tbid. c. 6, 272, », 21 sqq.
Phyt. vi. 7, 238, a, 36.
4
Aristotle's words are : oi
yap o5 juTjSez/ c|w, a\?C ot aei rt
e£« cotI, tout' foreipoV iaTtv,
where, however, the antithesis is
merely verbal, uv liriSiv e|to
'
meaning that beyond which
nothing exists,' ov ael ri e£u, on
the other hand, 'that of which a
part always remains beyond.'
5 P/iys.iii. 6 : see at p. 350, sup.
Gen. An. i. 715, b, 14 : ri Si i