Body and soul are not two different things, but only two different ways of perceiving the same thing. Similarly, physics and psychology are only different attempts to link our experiences together by way of systematic thought.

A life directed chiefly toward the fulfillment of personal desires will sooner or later always lead to bitter disappointment.

Man is, at one and the same time, a solitary being and a social being.

A country cannot simultaneously prepare and prevent war.

The Universe is difficult to comprehend because it is obvious.

Only six men in the world know about relativity. I am not one of them. When I ask them to explain, they confused me.

One cannot deal with a problem with the same thinking that creates it.