I made one great mistake in my life-when I signed the letter to President Roosevelt recommending that atom bombs be made but there was some justification-the danger that the Germans would make them.

Imagination is vastly more important than intelligence.

The thing is, not to stop questioning.

Pure logical thinking cannot yield us any knowledge of the empirical world. All knowledge of reality starts from experience and ends in it.

There does, in fact, appear to be a plan.

To get to know a country, you must have direct contact with the earth. It's futile to gaze at the world through a car window.

The right to search for truth implies also a duty.