d the effects of which we behold in the
chemical changes in the brain-substance itself after severe thinking.
This being so, it has been said, Why not suppose that so-called
subconscious actions _are_ merely brain activities which take place, but
which have never risen into consciousness? Professor Muensterberg and
others hold this view. It has been conclusively shown, however, by Dr.
Morton Prince and others, that this theory fails to explain adequately
many of the facts--seems indeed contrary to much experimental evidence;
and this view is now given up by all but the most materialistic of the
modern psychological school. We have to search deeper yet for the
mystery of the subconscious mind; and we shall have to grant it a
certain amount of consciousness of its own, apart from all purely brain
activity.

A very opposite theory is that advanced by Mr. F. W. H. Myers--that of
the "subliminal self." This theory says that the conscious mind is but
an infinitely small part of our total self--a mere fragment; that
portion best adapted to meet the needs of everyday life. To borrow an
analogy from physics, "consciousness is only the visible portion of the
spectrum; the invisible, ultra portions are our subconscious selves." I
shall not venture upon a criticism of this theory beyond saying that the
majority of modern psychologists do not hold to it; and hence, whether
it be ultimately true or false, we must disregard it for our present
purposes.

Thirdly, there is the theory that the subconscious mind is composed
entirely of dissociated or split-off ideas--ideas which have been
dissociated or split off from the main stream of consciousness, much as
a few freight cars might be shunted on to a side track by the
switch-engine. This hypothesis is very similar to another theory, which
contends that the subconsciousness consists of dissociated
experiences--mental happenings which have been forgotten or passed
beyond voluntary recall. For these mental states, or rather trains of
thought, Prince has suggested the term "co-conscious," because they are
conscious processes in operation at the same time as the normal
consciousness. This theory is doubtless far nearer an adequate
explanation of the facts than that which contends that the subconscious
is merely a portion of the field of consciousness which happens to lie
outside the field of _attention_, because _that_ is a theory certainly
inadequate to cover the facts. This last hypothes