complex
systems of motion; and bodies, all agree, are aggregates of
atoms. It seems to follow that the ground of reality, from the
point of view of physics, is motion. In short, as Heracleitus
taught, the world is the result of ceaseless motion. Tyndall's
doctrine of "heat as a mode of motion" is being generalised until
it covers the whole field of material phenomena. Or approach
the theory of Heracleitus from the side of modern astronomy,
the harmony between old and new is equally striking. All
substances, said he, spring from fire and to fire they are bound
to return. It does not require much special knowledge to realise
that this statement contains the pith of the latest theories of the
birth and death of worlds. From fire-mist, says the modern
astronomer, they were condensed, and to fire-mist, by collisions
or otherwise, they will return. What the particular stages may
be, what the significance of the nebula;, what the cosmic
functions of electricity, and other like problems--may be, and
will be, matter for keen debate. But the grand generalisation
remains--from fire-mist back again to fire-mist. How modern,
also, the grand unity which such a theory gives to existence as a
whole. Physics, psychology, sociology, even spiritual facts, all
come under the sway of the vast generalisation, because all
concerned with the same ultimate Reality. The most striking
parallel is found, perhaps, in the doctrine of Energy, which is
attracting so much attention at the present time, and of which
Ostwald is a champion so doughty. It embodies an attempt to
bring into one category the various physical forces together with
the phenomena of organic evolution, of psychology, and of
sociology in the largest sense. Whether the attempt is successful
or not, it is a tribute to the genius of the ancient sage, though it
seems to lack that definite element of consciousness, or soul-life,
which was so adequately recognised by its great predecessor.

Many other points in the system of Heracleitus are worthy of
the closest study. Intensely interesting, for example, is his
doctrine that strife is the condition of harmony, and indeed of
existence. Schelling reproduced this idea in his well-known
theory of polarity; Hegel developed it in his dialectic triad--
Thesis, Antithesis, Synthesis; and the electrical theories of
matter and force now in vogue fall easily into line with it--not to
speak of the dominant theory of evolution as involving a
stru