If we once allow ourselves to wonder whether we have turned off the
water, enclosed the check, or mailed the letter, it is but a step to an
uncomfortable frame of mind which can be relieved only by investigating the
matter. This compulsion once acceded to, it becomes more and more easy to
succumb. The next step is to blur, by constant repetition, the mental image
of the act. In extreme cases the doubter, after turning the gas on and off
a dozen times, is finally in doubt whether he can trust his own senses. A
certain officer in a bank never succeeded in reaching home after closing
hours without returning to try the door of the bank. Upon finding it
locked, he would unlock it and disappear within, to open the vault, inspect
the securities, and lock them up again. I once saw a victim of this form of
doubt spend at least ten minutes in writing a check, and ten minutes more
inspecting it, and, after all, he had spelled his own name wrong!

Constant supervision only impairs acts which should have become automatic.
We have all heard of the centipede who could no longer proceed upon his
journey when it occurred to him to question which foot he should next
advance.

To other doubts are often added the doubt of one's own mental balance;
but it is a long step from these faulty habits of mind to real mental
unbalance, which involves an inability to plan and carry out a line of
conduct consistent with one's station.

It took a young man at least fifteen minutes, in my presence, to button his
waistcoat. He felt the lower button to reassure himself, then proceeded
to the next. He then returned to the lower one, either distrusting his
previous observation, or fearing it had become unbuttoned. He then held the
lower two with one hand while he buttoned the third with the other. When