clouds. Little wonder that the thinker whose science carried him
to such scepticism as this should have felt the wrath of the
superstitious Athenians.


Biological Speculations

Passing from the phenomena of the air to those of the earth
itself, we learn that Anaxagoras explained an earthquake as being
produced by the returning of air into the earth. We cannot be
sure as to the exact meaning here, though the idea that gases are
imprisoned in the substance of the earth seems not far afield.
But a far more remarkable insight than this would imply was shown
by Anaxagoras when he asserted that a certain amount of air is
contained in water, and that fishes breathe this air. The passage
of Aristotle in which this opinion is ascribed to Anaxagoras is
of sufficient interest to be quoted at length:

"Democritus, of Abdera," says Aristotle, "and some others, that
have spoken concerning respiration, have determined nothing
concerning other animals, but seem to have supposed that all
animals respire. But Anaxagoras and Diogenes (Apolloniates), who
say that all animals respire, have also endeavored to explain how
fishes, and all those animals that have a hard, rough shell, such
as oysters, mussels, etc., respire. And Anaxagoras, indeed, says
that fishes, when they emit water through their gills, attract
air from the mouth to the vacuum in the viscera from the water
which surrounds the mouth; as if air was inherent in the
water."[2]

It should be recalled that of the three philosophers thus
mentioned as contending that all animals respire, Anaxagoras was
the elder; he, therefore, was presumably the originator of the
idea. It will be observed, too, that Anaxagoras alone is held
responsible for the idea that fishes respire air through their
gills, "attracting" it from the water. This certainly was one of
the shrewdest physiological guesses of any age, if it be regarded
as a mere guess. With greater justice we might refer to it as a
profound deduction from the principle of the uniformity of
nature.

In making such a deduction, Anaxagoras was far in advance of his
time as illustrated by the fact that Aristotle makes the citation
we have just quoted merely to add that "such things are
impossible," and to refute these "impossible" ideas by means of
metaphysical reasonings that seemed demonstrative not merely to
himself, but to many generations of his followers.

We are told that Anaxagoras alleged that all animals were
originally generated out of moisture, heat, and earth particles.
Just what opinion he held concerning man's development we are not
informed. Yet there is one of his phrases which
suggests--without, perhaps, quite proving--that he was an
evolutionist. This phrase asserts, with insight that is fairly
startling, that man is the most intelligent of animals because he
has hands. The man who could make that assertion must, it would
seem, have had in mind the idea of the development of
intelligence through the use of hands-- an idea the full force of
which was not evident to subsequent generations of thinkers until
the time of Darwin.


Physical Speculations

Anaxagoras is cited by Aristotle as believing that "plants are
animals and feel pleasure and pain, inferring this because they
shed their leaves and let them grow again." The idea is fanciful,
yet it suggests again a truly philosophical conception of the
unity of nature. The man who could conceive that idea was but
little hampered by traditional conceptions. He was exercising a
rare combination of the rigidly scientific spirit with the
poetical imagination. He who possesses these gifts is sure not to
stop in his questionings of nature until he has found some
thinkable explanation of the character of matter itself.
Anaxagoras found such an explanation, and, as good luck would
have it, that explanation has been preserved. Let us examine his
reasoning in some detail. We have already referred to the claim
alleged to have been made by Anaxagoras that snow is not really
white, but black. The philosopher explained his paradox, we are
told, by asserting that snow is really water, and that water is
dark, when viewed under proper conditions--as at the bottom of a
well. That idea contains the germ of the Clazomenaean
philosopher's conception of the nature of matter. Indeed, it is
not unlikely that this theory of matter grew out of his
observation of the changing forms of water. He seems clearly to
have grasped the idea that snow on the one hand, and vapor on the
other, are of the same intimate substance as the water from which
they are derived and into which they may be again transformed.
The fact that steam and snow can be changed back into water, and
by simple manipulation cannot be changed into any other
substance, finds, as we now believe, its true explanation in the
fact that the molecular structure, as we phrase it--that is to
say, the ultimate particle of which water is composed, is not
changed, and this is precisely the explanation which Anaxagoras
gave of the same phenomena. For him the unit particle of water
constituted an elementary body, uncreated, unchangeable,
indestructible. This particle, in association with like
particles, constitutes the substance which we call water. The
same particle in association with particles unlike itself, might
produce totally different substances--as, for example, when water


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