of the soul, as we find it amongst primitive peoples, but also in the
systems of the dualistic philosophers of to-day, is refuted by them.
According to these systems, the soul of man (and of the higher animals)
is a separate entity, which inhabits and rules the body only during its
individual life, but leaves it at death. The widespread "piano-theory"
(_Claviertheorie_) compares the "immortal soul" to a pianist who executes
an interesting piece--the individual life--on the instrument of the
mortal body, but at death withdraws into the other world. This "immortal
soul" is usually represented as an immaterial being; but in fact it is
really thought of as quite material, only as a finer invisible being,
aerial or gaseous, or as resembling the mobile, light, and thin substance
of the ether, as conceived by modern physics. The same is true also for
most of the conceptions which rude primitive peoples and the uneducated
classes among the civilised races have, for thousands of years, cherished
as to spectral "ghosts" and "gods." Serious reflection on the matter
shows that here--as in modern spiritualism--it is not with really
immaterial beings, but with gaseous, invisible bodies, that we are
dealing. And further, we are utterly incapable of imagining a truly
immaterial being. As Goethe clearly said, "matter can never exist or act
apart from spirit, neither can spirit apart from matter."

As regards immortality, it is well known that this important idea is
interpreted and applied in a great variety of ways. It is often made a
reproach against our Monism that it altogether denies immortality; this,
however, is erroneous. Rather do we hold it, in a strictly scientific
sense, as an indispensable fundamental conception of our monistic
philosophy of nature. Immortality in a scientific sense is conservation
of substance, therefore the same as conservation of energy as defined by
physics, or conservation of matter as defined by chemistry. The cosmos as
a whole is immortal. It is just as inconceivable that any of the atoms of