o questions him. When these conditions are
fulfilled, recourse to this method is perfectly legitimate, but the
conditions must be fulfilled. This is not a weapon for convenience, but
for necessity. It is easy to deceive oneself when it is painful to tell
the truth. Therefore it should be used sparingly: it is not for
every-day use, only emergencies of a serious nature can justify its
employ. Another artifice, still more delicate and dangerous, but just as
legitimate when certain conditions are fulfilled, is what is known as
mental restriction. This too consists in the employ of words of double
meaning; but whereas in the former case, both meanings are naturally
contained in the word, here the term employed has but one natural
signification, the other being furnished by circumstances. Its
legitimate use supposes that he to whom the term is directed should
either in fact know the circumstances of the case that have this
peculiar significance, or that he could and should know them. If the
information drawn from the answer received is insufficient, so much the
better; if he is misinformed, the fault is his own, since neither
genuine falsehood nor evident injustice can be attributed to the other.

An example will illustrate this better than anything else. Take a
physician or lawyer, the custodian of a professional secret, or a
priest with knowledge safeguarded by the seal of the confessional.
These men either may not or should not reveal to others unconcerned in
the matter the knowledge they, possess. There is no one but should be
aware of this, but should know that when they are questioned, they will
answer as laymen, and not as professionals. They will answer according
to outside information, yes or no, whether on not such conclusion agree
with the facts they obtained under promise of secrecy. They simply put
out of their mind as unserviceable all professional knowledge, and
respond as a man to a man. Their standing as professional men puts
every questioner on his guard and admonishes him that no private
information need be expected, that he must take the answer given as the
conclusion of outside evidence, then if he is deceived he has no one to
blame but himself, since he was warned and took no heed of the warning.

Again we repeat, the margin between mental restriction and falsehood is
a safe, but narrow one, the least bungling may merge one into the
other. It requires tact and judgment to know when it is permissible to