The fundamental thing about human languages is that they can and should be used to describe something; and this something is, somehow, the world. To be constantly and almost exclusively interested in the medium - in spectacle-cleaning - is a result of a philosophical mistake.

A theory is just a mathematical model to describe the observations.

Science is not a system of certain, or -established, statements; nor is it a system which steadily advances towards a state of finality... And our guesses are guided by the unscientific, the metaphysical (though biologically explicable) faith in laws, in regularities which we can uncover-discover. Like Bacon, we might describe our own contemporary science-'the method of reasoning which men now ordinarily apply to nature'-as consisting of 'anticipations, rash and premature' and as 'prejudices'.

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.

No rational argument will have a rational effect on a man who does not want to adopt a rational attitude.

Whenever a theory appears to you as the only possible one, take this as a sign that you have neither understood the theory nor the problem which it was intended to solve.