I
Quite a number of delusions find a common point of origin in the
natural tendency to view our mental life--the aggregate of our
thoughts and doings--as coextensive with the experiences of which
our consciousness gives information and which our will directs.
The significance of the unconscious and the involuntary is apt to
be underestimated or disregarded. We are more ready to acknowledge
that in certain unusual and semi-morbid conditions persons will
exhibit these peculiar expressions of the subterranean strata
of our mental structure--that some have the habit of walking or
talking in their sleep, that others occasionally fall into an
automatic, trance-like condition, that hypnotism and hysteria and
obscure lapses of consciousness and alterations of personality
bring to the surface curious specimens of the mysteries of this
underworld,--but we are slow to appreciate that the subconscious and
the involuntary find a common and a natural place amidst the soundly
reasoned and aptly directed activities of our own intelligence.
While it is reasonable and proper to have faith in the testimony
of consciousness, it is desirable that this confidence should be
accompanied by an understanding of the conditions under which such
testimony is presumably valid, and when presumably defective or
misleading. Sense-deceptions, faulty observation, distraction,
exaggeration, illusion, fallacy, and error are not idle abstract
fancies of the psychologist, but stern realities; and their existence
emphasizes the need in the determination of truth and the maintenance
of a sound rationality, of a calm, unprejudiced judgment, of an
experienced and balanced intelligence, of a discerning sense for nice
distinctions, of an appreciation of the circumstances under which it
is peculiarly human to err. A demonstration of the readiness with
which perfectly normal individuals may be induced to yield visible
evidence of unconscious and involuntary processes, thus possesses a
special interest; for when the naturalness of a few definite types
of involuntary movements is made clear, the application of the
experience to more complex and more indefinite circumstances will
easily and logically follow. While the circumstances under which
involuntary indications of mental activity are ordinarily given,
are too various to enable one to say _ab uno disce omnes_, yet the
principle demonstrated in one case is capable of a considerable
generalization, which will go far to prevent misconception of
apparently mysterious and exceptional phenomena.