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

'
PHYSICS 439
inite spaces traversed in a finite time that motion has
do—whereas infinite spaces are only said to be
raversed in the same sense in which the time of motion
3 infinite '—he establishes the indivisibility of the
iresent moment, and concludes that in this unit neither
lotion nor rest are possible. 2 He discusses the divisiility
of motion and of the body moved, 3 remarking that
very alteration attains completion in an indivisible
loment, but that the moment of its beginning is never
apable of being accurately determined. 4 He shows that
; is equally impossible to measure a merely finite space
1 infinite time or an infinite space in finite time, and
ansequently that an infinite magnitude cannot move
ay distance at all in a finite time. 5
These conclusions
ipply him with the means of refuting Zeno's argulents
against motion, 6 and enable him to prove that
le indivisible can neither move nor change in any way. 7
inally, he prepares the way for investigating tho
lovement of the universe and its cause, by asking 8
hether there can be a single movement of infinite
iration.
After establishing the eternity of motion and
1
Phys. vi. 2, 233, a, 13 sqq. m. and Thehlst. Phys. 55, a, m.,
2 Ibid. c. 3, and again c. 8, that difficulties had already suglere
he adds : in the transition gested themselves to Theophrasjm
motion to rest, the motion tus and Eudemus in connection
its as long as the transition with this view.
its j while, therefore, a thing is
5
Phys. vi. 7 ; cf . p. 429, n. 3,
ming to rest, it is moving still, supra. Aristotle shows, PhysMii.
3 Ibid. c. 4 (cf. also p. 430,n. 2). 9, 265, b, in, that his predecessors
rtion according to this passage also treated motion in space as
divisible in a double sense : the most primary,
6
st in respect of the time occu- Phys. vi. 9, cf. c. 2, 233, a,
id, and secondly in respect of 21, viii. 8, 263, a, 4, and p. 311,
i object moved.
supra.
* 7
Ibid. c. 5, 6. We see from Phys. viii. 10.
mpl. Phys. 230, a, m. 231, b, " At the end of this chapter.
ARISTOTLE
e necessity of a primum movens, he gives this answer :
there is a continuous and single movement without
iginning or end, it must be movement in space, for
)t only does this precede every other, 2 but every other
a transition between opposites
;
3
and where this is the
se the first motion ceases at a certain point, at which
new movement may begin in another direction, but
te and the same cannot continue without a break. 4
le same argument proves that only circular motion
iswers all the necessary requirements. If all moveent
in space must be either in a straight line, or
rcular, or mixed, 5 a mixed movement could only be of
Ldless duration and continuous if both the others
uld. Movement in a straight line cannot have
is character, since every finite rectilinear movement G
ts terminal points at which it ceases, and though
>tween these terminal points it may be infinitely often
peated, yet these repeated movements do not conitute
one continuous motion. Circular motion is,
erefore, the only kind of movement which, continuing
te
and the same in unbroken sequence, can be without
jginning and end. 7 It unites the repose of the unisrse
with unceasing motion, since it enables it to move
1
Phjs. viii. 1-6 see p. 387 ' IMd. 261, a, 31
supra.
;
5
sqq.
Among mixed forms of mo-
2
Phys. viii. 7 ; see p. 423 sq. tion we must in this division
!»'«.
reckon all curvesexceptthecircle.
3
Generation from not-being
e
An infinite one is impossible,
being ; destruction from being not only in itself (see p. 430, n. 2,
not-being ; increase from less supra) but also because the world
greater ; decrease from greater is not infinite.
less ; alteration from one state ' All this is explained at
another, e.g. from water to length, Phys. viii. 8, 261, a, 27-
>am. 263. b, 3, 264, a, 7 sqq. c. 9 init.