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

The positive heuristic of the programme saves the scientist from becoming confused by the ocean of anomalies.

The classical example of a successful research programme is Newton's gravitational theory: possibly the most successful research programme ever.

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.

Our empirical criterion for a series of theories is that it should produce new facts. The idea of growth and the concept of empirical character are soldered into one.

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