Optimism is a duty. The future is open. It is not predetermined. No one can predict it, except by chance. We all contribute to determining it by what we do. We are all equally responsible for its success.

No number of sightings of white swans can prove the theory that all swans are white. The sighting of just one black one may disprove it.

The question is not how to get good people to rule; THE QUESTION IS: HOW TO STOP THE POWERFUL from doing as much damage as they can to us.

Definitions.... are never really needed, and rarely of any use

Every genuine test of a theory is an attempt to falsify it, or to refute it.

The moral decisions of others should be treated with respect, as long as such decisions do not conflict with the principle of tolerance.

There is no history, only histories.