We accumulate our opinions at an age when our understanding is at its weakest.

A book which, above all others in the world, should be forbidden, is a catalogue of forbidden books.

Delight at having understood a very abstract and obscure system leads most people to believe in the truth of what it demonstrates.

To do just the opposite is also a form of imitation.

Pain warns us not to exert our limbs to the point of breaking them. How much knowledge would we not need to recognize this by the exercise of mere reason.

The writer who cannot sometimes throw away a thought about which another man would have written dissertations, without worry whether or not the reader will find it, will never become a great writer.

Prejudices are so to speak the mechanical instincts of men: through their prejudices they do without any effort many things they would find too difficult to think through to the point of resolving to do them.