It may afford consolation to know that insanity results, in the majority
of cases, from physical disease of the brain, and that it is ordinarily
unanticipated, unsuspected and uncredited by the patient. There is no more
danger of insanity attacking the worrier and the delicate than the robust
and the indifferent. In fact, the temperament which produces the faulty
habits we are considering rarely culminates in insanity. It seems worth
while, however, to replace the vague fear of insanity by a knowledge of the
variety of mental unbalance remotely threatening the person who lacks the
desire or the will, to place a check upon these faulty habits of mind. We
may thus, in the worrier whose fears have taken this direction, substitute
effort for foreboding.

It is our _conduct_ rather than our thoughts that determines the question
of insanity. The most practical definition of insanity I know is that of
Spitzka, the gist of which is that a person is insane who can no longer
correctly register impressions from the outside world, or can no longer act
upon those impressions so as to formulate and carry out a line of conduct
consistent with his age, education and station.

The banker may repeat the process of locking and unlocking, even to
the point of doubting his own sensations, but he may still be able to
formulate, and carry out, a line of conduct consistent with his position,
though at the expense of intense mental suffering.

In the realm of morbid fears, the person obsessed by fear of contamination
shows no sign of insanity in using tissue paper to turn the door-knob, or
in avoiding objects that have been touched by others. Up to this point
his phobia has led merely to eccentricity, but suppose his fear so far
dominates him that he can no longer pursue his occupation for fear of