Gradually the conviction gained recognition that all knowledge about things is exclusively a working-over of the raw material furnished by the senses. ... Galileo and Hume first upheld this principle with full clarity and decisiveness.

It seems to me an utterly futile task to prescribe rules and limitations for the conduct of war. War is not a game; hence one cannot wage war by rules as one would in playing games. Our fight must be against war itself. The masses of people can most effectively fight the institution of war by establishing an organization for the absolute refusal of military service.

Discussion and argument are essential parts of science; the greatest talent is the ability to strip a theory until the simple basic idea emerges with clarity.

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

If one holds these high principles clearly before one's eyes, and compares them with the life and spirit of our times, then it appears glaringly that civilized mankind finds itself at present in grave danger. In the totalitarian states it is the rulers themselves who strive actually to destroy that spirit of humanity. In less threatened parts it is nationalism and intolerance, as well as the oppression of the individuals by economic means, which threaten to choke these most precious traditions.

What is inconceivable about the universe is that it is at all conceivable.

Once you can accept the universe as matter expanding into nothing that is something, wearing stripes with plaid comes easy.