The only true wisdom is in knowing you know nothing.

The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge.

Imagine the end desired and feel its reality. Follow it through, and you will get definite results.

I am not an Athenian or a Greek, but a citizen of the world.

A clever person solves a problem. A wise person avoids it.

My brain is only a receiver, in the Universe there is a core from which we obtain knowledge, strength and inspiration. I have not penetrated into the secrets of this core, but I know that it exists.

I have no special talents. I am only passionately curious.

If you can't explain it to a six year old, you don't understand it yourself.

Only a life lived for others is a life worthwhile.