Isn't it strange that I who have written only unpopular books should be such a popular fellow?

The strength of the Constitution lies entirely in the determination of each citizen to defend it. Only if every single citizen feels duty bound to do his share in this defense are the constitutional rights secure.

The thinking that got us to where we are is not the thinking that will get us to where we want to be.

Nature conceals her mystery by her essential grandeur.

Imagination is the most powerful force in the universe.

Energy cannot be created or destroyed, it can only be changed from one form to another.

I want to know the thoughts of God. Everything else is just details.