People say sometimes--"Common sense is very rare." What does this phrase
signify? that in many men reason set in operation is stopped in its
progress by prejudices, that such and such man who judges very sanely in
one matter, will always be vastly deceived in another. This Arab, who
will be a good calculator, a learned chemist, an exact astronomer, will
believe nevertheless that Mohammed put half the moon in his sleeve.

Why will he go beyond common sense in the three sciences of which I
speak, and why will he be beneath common sense when there is question of
this half moon? Because in the first cases he has seen with his eyes,
he has perfected his intelligence; and in the second, he has seen with
other people's eyes, he has closed his own, he has perverted the common
sense which is in him.

How has this strange mental alienation been able to operate? How can the
ideas which move with so regular and so firm a step in the brain on a
great number of subjects limp so wretchedly on another a thousand times
more palpable and easy to comprehend? This man always has inside him the
same principles of intelligence; he must have some organ vitiated then,
just as it happens sometimes that the finest _gourmet_ may have a
depraved taste as regards a particular kind of food.

How is the organ of this Arab, who sees half the moon in Mohammed's
sleeve, vitiated? It is through fear. He has been told that if he did
not believe in this sleeve, his soul, immediately after his death, when
passing over the pointed bridge, would fall for ever into the abyss. He
has been told even worse things: If ever you have doubts about this
sleeve, one dervish will treat you as impious; another will prove to you
that you are an insensate fool who, having all possible motives for
believing, have not wished to subordinate your superb reason to the