muscular, and in the other it is nervous. When we speak of mental or
spiritual force, we have as distinct a conception as when we speak of
physical force. It requires physical force to produce the effect that we
call mental force, though how the one can result in the other is past
understanding. The law of the correlation and conservation of energy
requires that what goes into the body as physical force must come out in
some form of physical force--heat, light, electricity, and so forth.

Science cannot trace force into the mental realm and connect it with our
states of consciousness. It loses track of it so completely that men
like Tyndall and Huxley and Spencer pause before it as an inscrutable
mystery, while John Fiske helps himself out with the conception of the
soul as quite independent of the body, standing related to it as the
musician is related to his instrument. This idea is the key to Fiske's
proof of the immortality of the soul. Finding himself face to face with
an insoluble mystery, he cuts the knot, or rather, clears the chasm, by
this extra-scientific leap. Since the soul, as we know it, is
inseparably bound up with physical conditions, it seems to me that a
more rational explanation of the phenomenon of mentality is the
conception that the physical force and substance that we use up in a
mental effort or emotional experience gives rise, through some unknown
kind of molecular activity, to something which is analogous to the
electric current in a live wire, and which traverses the nerves and
results in our changing states of consciousness. This is the mechanistic
explanation of mind, consciousness, etc., but it is the only one, or
kind of one, that lends itself to scientific interpretation. Life,
spirit, consciousness, may be a mode of motion as distinct from all
other modes of motion, such as heat, light, electricity, as these are
distinct from each other.