, 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 is taken up by the roots of a plant and becomes, seemingly,
a part of the substance of the plant. But whatever the changed
association, so Anaxagoras reasoned, the ultimate particle of water
remains a particle of water still. And what was true of water was true
also, so he conceived, of every other substance. Gold, silver, iron,
earth, and the various vegetables and animal tissues--in short, each and
every one of all the different substances with which experience makes us
familiar, is made up of unit particles which maintain their integrity in
whatever combination they may be associated. This implies, obviously, a
multitude of primordial particles, each one having an individuality of
its own; each one, like the particle of water already cited, uncreated,
unchangeable, and indestructible.

Fortunately, we have the philosopher's own words to guide us as to his
speculations here. The fragments of his writings that have come down
to us (chiefly through the quotations of Simplicius) deal almost
exclusively with these ultimate conceptions of his imagination.
In ascribing to him, then, this conception of diverse, uncreated,
primordial elements, which