It would be wrong to assume that one must stay with a research programme until it has exhausted all its heuristic power, that one must not introduce a rival programme before everybody agrees that the point of degeneration has probably been reached.

Intellectual honesty consists in stating the precise conditions under which one will give up one's belief.

Research programmes, besides their negative heuristic, are also characterized by their positive heuristic.

Man's respect for knowledge is one of his most peculiar characteristics. Knowledge in Latin is scientia, and science came to be the name of the most respectable kind of knowledge.

Philosophy of science without history of science is empty; history of science without philosophy of science is blind.

That sometimes clear ... and sometimes vague stuff ... which is ... mathematics.

Indeed, this epistemological theory of the relation between theory and experiment differs sharply from the epistemological theory of naive falsificationism.