Of course I don't believe in it [pointing to horseshoe on his office wall]. But I understand that it brings you luck whether you believe in it or not.

A deep truth is a truth so deep that not only is it true but it's exact opposite is also true.

Your theory is crazy, but it's not crazy enough to be true.

If we couldn't laugh at ourselves, that would be the end of everything.

Every valuable human being must be a radical and a rebel, for what he must aim at is to make things better than they are.

If anybody says he can think about quantum physics without getting giddy, that only shows he has not understood the first thing about them.

Every great and deep difficulty bears in itself its own solution. It forces us to change our thinking in order to find it.