ve its
place. But Heracleitus has a further thought which is in full
harmony with the nature-mystic's chief contention. He holds
that _sense perception_ is also a medium, for the outer fire is
thereby absorbed by the inner fire. The value of this thought
remains in spite of the sage's doctrine of the body. For though
the body is regarded by him as a clog on the activity of the inner
fire, because it consists of water and earth (two forms in which
the movement of the Fire is greatly reduced) it is nevertheless
akin to the soul, and is itself destined, in the course of ceaseless
change, to become Fire in its most living and active form.

Such is the central doctrine of this noted thinker, round which
all his other teaching turned. Let us now ask, as in the
corresponding cases of Thales and Anaximander, why the
particular element was chosen as the Ground of all things. The
answer to this question will furnish, as in the previous cases,
much matter for our special purpose, since the emphasis will lie
rather on the physical properties and functions of fire, than on
its more abstract ontology.

It is obvious that Heracleitus would start with a knowledge of
the speculations of his more immediate predecessors, and of the
data on which they were based--the phenomena of circulation in
nature, evaporation, mist, rain, melting, freezing, and the rest.
And we find that in this direction he merely amplified the older
systems, taking fire, instead of water or air, as his _Welt-stoff_.
He also observed, with special care, certain suggestive cases of
rarefaction by heat and condensation by cold; as also the facts
of constant decomposition and renewal in the vegetable and
animal worlds. But the phenomenon which stands out as the
chiefest determinant of his thought is one which is always
bound to act as a powerful stimulant on a thoughtful mind--that
of combustion.

The flame of an ordinary fire can still be a thing of wonder to
the man whose mind is open to receive impressions even from
the commonplace. How illusive it is!--dancing, darting,
flickering, flashing--appearing, disappearing--unsubstantial yet
active and almost miraculously potent. The effect upon the
mind of primitive man must have been keen and vivid to the
highest degree, and must have produced results of corresponding
significance upon his spiritual development.

But the deeper kind of wonder is reserved for the systematic
speculative thinker, whose attention is a