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

i unite
FHYSICS 447
•
ict, which is what the Atomists deny. 1 In the same
ray a reciprocal influence would exist between them
"certain qualities—like warmth, for instance—were
Dupled with a certain shape ; it is, however, equally
npossible to
imagine the atoms without qualities and
) suppose them endowed with definite properties. 2
Lgain, there is no reason why there should be only small
nd invisible atoms and not also large ones. 3 Lastly, if
ae atoms are moved by another power, they experience
u influence, and their apathy is destroyed: if they
love themselves, the motive force is either inside them
nd different from what is moved—in which case
they
re not indivisible—or opposite properties are united
a one and the same object. 4
Again, Aristotle believed that Democritus was quite
s unable as Plato to explain the physical qualities of
hings. The one makes fire spherical, the other pyramidal
in form, but both are equally wrong. 8 Aritotle,
however, derives his most conclusive argument
gainst the homogeneity of matter from the very pheomenon
by which modern science is accustomed to
upport it—the phenomenon of gravity.
Democritus,
ke Aristotle, was ignorant that all bodies mutually
ttract each other, that within the terrestrial atmophere
they all gravitate to the centre of the earth, that
le inequality in the rate of their descent is
1
Gen. et Corr. i. 8, 326, a, *
Ibid. 326, b, 2.
caused by
) sqq., to which, however, it "
In the passage quoted p.
ight be replied that they refuse 445, n. 4, supra, Aristotle attacks
because they are not both views alike and on the same
juid but solid bodies. grounds. Cf. alsq Gen, et Corr
' Ibid. 326, a, 1-24. j. 8, 326, a, 3.
s Ibid, at line 24.
4 48 ARISTOTLE
the resistance of the air, and that the pressure of the
atmosphere occasions the ascent of fire, vapour, &c.
Democritus believed that all the atoms fall downwards
in the void, but that the greater fall
quicker than the
less, deducing from this hypothesis the concussion of the
atoms and the pressure by which the lesser are driven
upwards.
For the same reason, he held that the weight
of composite bodies, supposing their circumference equal,
corresponds to their magnitude after subtraction of the
empty interstices. 1 Aristotle demonstrates 2 that this
hypothesis is false : there is no above or beneath in
infinite space, and consequently no natural tendency
downwards ;
all bodies must fall with equal rapidity in
the void, 3 nor can the void within bodies make them
lighter than they really are. But being equally unacquainted
with the actual phenomena which have to be
explained, Aristotle repudiates the only true point in the
system of Democritus, in order to avoid the consequences
which he saw to
be implied in the Atomic hypothesis,
but the truth of which Democritus was as far from recognising
as he was. On the strength of what he assumed
to be facts, he opposes a theory which, originally speculative,
could only be supported by a verification of the facts
it had assumed, such as was wholly beyond the reach of
ancient science. It is true, as he says, that in a vacuum
everything must sink with equal rapidity ; but this
1
Cf. Zell. Ph. d. Gr. i. real advance upon the atomic
779 sq., 791 sq. theory, but only as a means .of
2
Phys. iv. 8, 214, b, 28 sqq. makinghisownarbitraryassump-
De Coelo, iv. 2, 308, a 34-309, a, tion of deviations in the atoms
18 ; see p. 428, n. 5, supra. comprehensible. Seep. 307, n. 4,
3
Epicurus, indeed, had re- supra.
cognised this, not, however, as a