Reason like science, grows by way of mutual criticism; the only possible way of planning its growth is to develop those institutions that safeguard. the freedom of thought

A rationalist is simply someone for whom it is more important to learn than to be proved right; someone who is willing to learn from others - not by simply taking over another's opinions, but by gladly allowing others to criticize his ideas and by gladly criticizing the ideas of others

Our belief in any particular natural law cannot have a safer basis than our unsuccessful critical attempts to refute it.

It must be possible for an empirical system to be refuted by experience.

It is the rule which says that the other rules of scientific procedure must be designed in such a way that they do not protect any statement in science against falsification.

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.

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.