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.

Genius is making complex ideas simple, not making simple ideas complex

Outer changes always begin with an inner change of attitude.

Applying the axioms of physical science to human life has something reprehensible to it.

It is true that the grasping of truth is not possible without empirical basis. However, the deeper we penetrate and the more extensive and embracing our theories become the less empirical knowledge is needed to determine those theories.

Man owes his strength in the struggle for existence to the fact that he is a social animal.

Out of the multitude of our sense experiences we take, mentally and arbitrarily, certain repeatedly occurring complexes of sense impression (partly in conjunction with sense impressions which are interpreted as signs for sense experiences of others), and we attribute to them a meaning the meaning of the bodily object.