Blind commitment to a theory is not an intellectual virtue: it is an intellectual crime.

The proving power of the intellect or the senses was questioned by the skeptics more than two thousand years ago; but they were browbeaten into confusion by the glory of Newtonian physics.

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

Blind commitment to a theory is not an intellectual virtue: it is an intellectual crime.

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.

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.