A gentleman once told me that he rarely passed another in the street
without wondering if he had not accosted him in an improper manner. He knew
very well that he had not, but the more he dwelt upon the possibility, the
more doubtful he became, until the impulse to settle the question became
so strong that he would retrace his steps and inquire. He asked if _nux
vomica_ would help this trouble! I told him he needed mental training.

"I have tried that," he answered. "I keep saying to myself, 'I will not
think of it,' but it is no use; my head becomes hot, my sight blurred, my
thoughts confused, and the only relief I find is to settle the question."

I tried to point out the direction in which he was tending, and told him he
must remind himself that even if he had accosted another improperly, it was
a trifling matter compared to the injury to himself of giving way to this
compulsion; moreover, the impression he would make upon the other by going
back would be even worse than that of having so accosted him; and, finally,
he must dwell upon the _probability_ that he had not offended the man,
instead of the _possibility_ that he had. Having pursued this line of
thought, he must force himself to think of something else until the
besetting impulse was obliterated. I suggested that if a baseball player
should become incapacitated for the game, he would not lessen his
disappointment by reiterating, "I will not think of baseball," but if he
persistently turned his thoughts and his practice to billiards he might in
time forget baseball.

"I never played baseball," he replied, "and don't even know the rules."

This represents an extreme case of "doubting folly" a case in which the
victim could no longer concentrate his thoughts on the simplest proposition
outside the narrow circle to which his doubts had restricted him.