The secret of change is to focus all of your energy, not on fighting the old, but on building the new.

The only true wisdom is in knowing you know nothing.

Ignorance, the root and stem of all evil.

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

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

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.

An honest man is always a child.

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

I cannot teach anybody anything. I can only make them think.