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

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PHYSICS 479
rises above all other bodies. Water and air, on the
other hand, are only relatively heavy, and therefore also
relatively light. Water is heavier than air and fire,
but lighter than earth ; air heavier than fire, but lighter
than water and earth. Under no possible circumstances,
unless compelled by forcible movement, does fire sink of
itself into the place of air ; nor, again, does earth rise
into that of water. Air and water, on the contrary,
sink into the lower regions when the matter which fills
them is withdrawn. 1 Earth is everywhere heavy; water,
everywhere except in earth ;
earth
and water
2
air, everywhere except in
fire, nowhere. 3 Therefore of two
bodies the one which holds the more air may be heavier
in air but lighter in water than the other— a hundredweight
of wood, for instance, than a pound of lead. 4
We may arrive at these four elements even more
definitely by another process of reasoning. 5 All
1
Properly, indeed, they ought world cannot consist of sether
to rise into the higher ; Aristotle alone, for it must have an immovadmits
himself, Be CceU, iv. 5, able centre. There must there-
312, b, sqq., that this does happen fore be a body whose nature it is
unless external force be applied, to rest at the centre and move
—without, however, explaining a towards it, and therefore also one
circumstance which has so im- of an opposite nature. We thus
portant a bearing upon his have earth and fire, which in
theory. turn require water and air as
2
That even air has weight is intermediate elements,
obvious from the fact that a 5
For what follows, see Gen.
bladder full of airis heavierthan et Corr. ii. 2, 3. The true author
an empty one ; ibid. c. 4, 311, b, 9. of this theory of the elements is
3
Aristotle, in the passage said to be Hippocrates (according
just referred to, finds in this to IDELEK, Arist. Meteor, ii. 389,
theory an explanation of the who appeals to Galen, De Mem.
difference between absolute and sec. Sippocr. i. 9, Opp. ed. Kiihn,
specific gravity. i. 481 sq.). This, however, is un-
4
Be Ccelo, iv. 3-5. The same certain for several reasons. In
ideas occur, in a somewhat the first place, neither of the
different application, ii. 3, 286, a, works here referred to, n. Qicrios
12 sqq. It is there said that the hpBp&irov and n. aapicuv, can be
480 ARISTOTLE
bodies capable of being perceived by the senses are
prehensible ; but all qualities perceptible by the sense of
touch, with the exception of gravity and levity, 1 are
reducible to four—warmth, cold, dryness, moisture. 2
Aristotle regards the first two of these properties as
active, the others as passive. 3 Now, by joining these
attributed to Hippocrates. The
former is without doubt the
work, or an extract from a work,
of Polybus, his son-in-law : the
latter is of post-Aristotelian
origin, cf . Kuhn, Hippoer. Opp. I.
cxlvii., olv. ; Littre, (Euwes d'
Hippocrate, i. 345 sqq. 384.
Again, while the treatise n.