My internal and external life depend so much on the work of others that I must make an extreme effort to give as much as I receive.

It is certainly true that principles cannot be more securely founded than on experience and consciously clear thinking.

The only sure way to avoid making mistakes is to have no new ideas.

I have lived to prove Thoreau's contention that a man is rich in proportion to the number of things which he can afford to let alone.

Everyone must become their own person, however frightful that may be.

All these primary impulses, not easily described in words, are the springs of man's actions.

I don't teach my students, I provide the circumstances in which they can learn.