Alan Ebenstein, Hayek's Journey: The Mind of Friedrich Hayek (2003), Ch. 15. Karl Popper

I got to know Bertrand Russell in the last years of his life. I knew Karl Popper quite well, and they were a whole class above me in intelligence. It wasn’t that I was jealous, it was that I was trying to grapple with these problems with inadequate weaponry… Popper had this originality, Russell had it, and Einstein had it in spades.

I read Karl Popper's The Open Society and its Enemies. Popper, whose analysis in many ways complemented that of Hayek, approached Marxism from the point of view of the philosopher of the natural sciences. This meant that he was ideally equipped to expose the fraudulent claim of Marxists to have discovered immutable laws of history, social development or "progress" – laws which were comparable to the laws of natural science. It was not just that the "inevitable" course of events which Marx had prophesied had not occurred and showed no signs of occurring. Marx and Marxists had not even understood the scientific method, let alone practised it in their analysis. Unlike the Marxists – whether historians, economists or social scientists – who tried to "prove" their theories by accumulating more and more facts to sustain them, "the method of science is rather to look out for facts which may refute the theory... and the fact that all tests of the theory are attempted falsifications of predictions derived with its help furnishes the clue to scientific method". The political consequences of this basic error – perhaps more properly described as basic fraud – were summed up by Popper in the dedication of his later book The Poverty of Historicism: "In memory of the countless men, women and children of all creeds or nations or races who fell victims to the fascist and communist belief in Inexorable Laws of Historical Destiny."

Popper believed that any idea of Utopia is necessarily closed owing to the fact that it chokes its own refutations. The simple notion of a good society that cannot be left open for falsification is totalitarian. I learned from Popper, in addition to the difference between an open and a closed society, that between an open and a closed mind.

I do have a great respect for Popper. I mean, I think... he's nearer to... I mean, Popper's ambition, in relation to science, at least, was to discriminate between, sort of, science and what he called pseudo-science.

Popper was kind of an egocentric jerk.

The leading critic of the positivists in their heyday was of course Popper. There has been a tendency for philosophers of science to regard Popper as something of an embarrassment. However, naturalistic philosophers should take it as an interesting fact about science that Popper has long been the favourite philosopher of science among scientists; and it would be condescending to attribute this entirely to the fact that Popper's philosophy is relatively non-complex, self-contained, and flattering to scientists.

[T]he paradox lurking at the heart of Karl Popper's career... Everyone says this opponent of dogmatism is almost pathologically dogmatic. ...Popper scoffs at scientists’ hope that they can achieve a final theory of nature. "...I think we have gone very far, but we are much further away." He... returns with his book Conjectures and Refutations... [and] reads his own words with reverence: "In our infinite ignorance we are all equal." ...Can a skeptic avoid self-contradiction... the Popper paradox? And if he doesn’t, if he preaches but fails to practice intellectual doubt and humility, does that negate his work? Not at all. Such paradoxes corroborate the skeptic’s point... the quest for truth is endless, twisty and riddled with pitfalls, into which even sharp-eyed seekers tumble. In our infinite ignorance we are all equal.

Through my association with Popper I experienced a great liberation in escaping from the rigid conventions that are generally held with respect to scientific research. ... When one is liberated from these restrictive dogmas, scientific investigation becomes an exciting adventure opening up new visions; and this attitude has, I think, been reflected in my own scientific life since that time.

I learned from Popper what for me is the essence of scientific investigation—how to be speculative and imaginative in the creation of hypotheses, and then to challenge them with the utmost rigor, both by utilizing all existing knowledge and by mounting the most searching experimental attacks. In fact, I learned from him even to rejoice in the refutation of a cherished hypothesis, because that, too, is a scientific achievement and because much has been learned by the refutation.