ness of mental
and physical phenomena is so absolute that we must hesitate about
drawing any connection between them. It is impossible to conceive the
mental side of a sensation as a form of wave motion. If, further, we
take into consideration the other phenomena associated with the nervous
system, the more distinctly mental processes, we have absolutely no data
for any comparison. We can not imagine thought measured by units, and
until we can conceive of such measurement we can get no meaning from any
attempt to find a correlation between mental and physical phenomena. It
is true that certain psychologists have tried to build up a conception
of the physical nature of mind; but their attempts have chiefly resulted
in building up a conception of the physical nature of the brain, and
then ignoring the radical chasm that exists between mind and matter. The
possibility of describing a complex brain as growing parallel to the
growth of a complex mind has been regarded as equivalent to proving
their identity. All attempts in this direction thus far have simply
ignored the fact that the stimulation of a nerve, a purely physical
process, is not the same thing as a mental action. What the future may
disclose it is hazardous to say, but at present the mental side of the
living machine has not been included within the conception of the
mechanical nature of the organism.

==The Living Body is a Machine.==--Reviewing the subject up to this
point, what must be our verdict as to our ability to understand the
running of the living machine? In the first place, we are justified in
regarding the body as a machine, since, so far as concerns its relations
to energy, it is simply a piece of mechanism--complicated, indeed,
beyond any other machine, but still a machine for changing one kind of
energy into another. It receives the energy in the form of chemical
composition and converts it into heat, motion, nervous wave motion, etc.
All of this is sure enough. Whether other forms of nervous and mental
activity can be placed under the same category, or whether these must be
regarded as belonging to a realm by themselves and outside of the scope
of energy in the physical sense, can not perhaps be yet definitely
decided. We can simply say that as yet no one has been able even to
conceive how thought can be commensurate with physical energy. The utter
unlikeness of thought and wave motion of any kind leads us at present to
feel that on the side of