Sir Karl Popper is a philosopher whose work has influenced and stimulated that of virtually every student in the philosophy of science. In part this influence is explainable on the basis of the healthy-mindedness of some of Sir Karl's fundamental attitudes: ‘There is no method peculiar to philosophy’. ‘The growth of knowledge can be studied best by studying the growth of scientific knowledge.’

These attitudes are perhaps a little narrow (can the growth of knowledge be studied without also studying nonscientific knowledge? Are the problems Popper mentioned of merely theoretical interest – just ‘riddles’?), but much less narrow than those of many philosophers; and the ‘obscurantist faith’ Popper warns against is a real danger. In part this influence stems from Popper's realism, his refusal to accept the peculiar meaning theories of the positivists, and his separation of the problems of scientific methodology from the various problems about the ‘interpretation of scientific theories’ which are internal to the meaning theories of the positivists and which positivistic philosophers of science have continued to wrangle about (I have discussed positivistic meaning theory in chapter 14 and also in chapter 5, volume 2).