The genuine rationalist does not think that he or anyone else is in possession of the truth; nor does he think that mere criticism as such helps us achieve new ideas. But he does think that, in the sphere of ideas, only critical discussion can help us sort the wheat from the chaff.

There can be no ultimate statements science: there can be no statements in science which can not be tested, and therefore none which cannot in principle be refuted, by falsifying some of the conclusions which can be deduced from them.

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.

It is part of my thesis that all our knowledge grows only through the correcting of our mistakes.

Every discovery contains an irrational element or a creative intuition.

It is a myth that the success of science in our time is mainly due to the huge amounts of money that have been spent on big machines. What really makes science grow is new ideas, including false ideas.

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.