When a book and a head collide and a hollow sound is heard, must it always have come from the book?

It is a question whether, when we break a murderer on the wheel, we do not fall into the error a child makes when it hits the chair it has bumped into.

The great trick of regarding small departures from the truth as the truth itself - on which is founded the entire integral calculus - is also the basis of our witty speculations, where the whole thing would often collapse if we considered the departures with philosophical rigour.

One's first step in wisdom is to question everything - and one's last is to come to terms with everything.

A good part of the fame of most celebrated men is due to the shortsightedness of their admirers

When an acquaintance goes by I often step back from my window, not so much to spare him the effort of acknowledging me as to spare myself the embarrassment of seeing that he has not done so.

Be wary of passing the judgment: obscure. To find something obscure poses no difficult, elephants and poodles find many things obscure.