So far we have only considered the most obvious and simple among the
evidences of doubting folly. A still more obstinate tendency of the doubter
is the insistent habit interminably to argue over the simplest proposition,
particularly regarding matters pertaining to the health, comfort, and life
of the individual himself. A certain patient, of this type, attempts to
describe to his physician a peculiar, hitherto undescribed, and even now
indescribable sensation "through his right lung." He traces this sensation
to what he believes to have been the absorption of a poison some years ago.
His line of reasoning is somewhat as follows: 1. The drug was a poison. 2.
If he absorbed it he must have been poisoned. 3. If he was poisoned then,
he is poisoned now. 4. There is no proof that such a poison cannot produce
such a sensation. 5. He has the sensation. Conclusion: He is suffering from
poison. In support of this proposition he will spend hours with anyone
who will listen. The physician who allows himself to be drawn into the
controversy speedily finds himself, instead of giving advice to listening
ears, involved in a battle of wits in which he is quite likely to come
off second best. He assures the patient, for example, that, as far as
scientific methods can establish the fact, the lung is sound.

"But has science established everything? And if it had, is such negative
evidence to be weighed against the positive evidence of the sensation in my
lung?"

"But the sensation may not be in your lung."

"Can you prove that it is _not_ in my lung?" Folly scores!

On being urged to direct his attention to some other part of his body, he
promptly inquires,