“The only source of knowledge is experience.”

A man should look for what is, and not for what he thinks should be.

The only real valuable thing is intuition.

One may say the eternal mystery of the world is its comprehensibility.

We cannot solve our problems with the same thinking we used when we created them.

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

If A is success in life, then A equals x plus y plus z. Work is x; y is play; and z is keeping your mouth shut.