Karl Popper, philosopher of liberty

On July 29th, 1902, was born one of the most remarkable and influential philosophers of the 20th Century, Karl Raimund Popper. As a teenager in Vienna, Popper was attracted by Marxism, and at one stage thought of himself as a Communist. What disillusioned him was the realization that none of the precepts of Marxism could be tested.

He formed the view that there was a difference between the ideas of Marx, Freud and Adler, and those of Einstein. Einstein’s theory of relativity could be tested by observation, and indeed was tested by Eddington’s experiments in 1919. By contrast, those of Marx, Freud and Adler could accommodate everything that happened; there was nothing that could happen in the observed world that could refute them.

This led Popper to the ideas he published in his 1934 “Logik der Forschung,” published in English in 1959 as “The Logic of Scientific Discovery.” Here Popper advanced his central notion of falsification. He said that although a theory could not be proved true, because an experiment might one day come along to refute it, it could be proved false if an experiment contradicted its predictions. Einstein’s theory could have been refuted, but wasn’t, whereas those of Marx, Freud and Adler could not be subjected to experiments that might refute them. They represented a determination to interpret the world in certain ways, rather than being capable of adding to our knowledge of it.

Popper solved Hume’s problem of induction. We expect the sun to rise each day because it has done so every day so far, although there are no causal links to explain why the past indicates the future, and why induction is valid. Popper replaced induction by conjecture and refutation. We form a theory that the sun will rise tomorrow, and test it each day. If one day it didn’t, then our conjecture would be refuted. Our scientific knowledge is thus not what we know to be true, but the collection of theories that we have been unable to refute. Theories that cannot be tested like this are not necessarily nonsense, but they are not scientific.

Popper’s other great influential work was his 1945 “The Open Society and its Enemies,” in which Vol 1 was “The Spell of Plato,” and Vol 2 was “Hegel and Marx.” Popper called it his “war book,” but it remains one of the most powerful demolitions of totalitarian ideology ever written. Far from being interested in “justice” and “virtue,” Plato was in fact justifying rule by the superior élite, and is profoundly anti-democratic and pro censorship and thought control. As Popper says, Plato’s idea of virtue is “the ruler rules, the worker works, and the slave slaves.” And Hegel and Marx enlist fanciful notions of where historical destiny is taking us to justify oppression and control. Popper opts instead for “piecemeal social engineering,” by which we gradually improve our circumstances by building on what has worked and making it better by removing some of its shortcomings. Democracy is not about choosing those best fitted to rule; it is about removing those who are bad or incompetent.

I was never happy with Popper’s idea that things could be “proved” false, thinking it subject to the same flaws as “proving” them to be true. We can decide to discard theories that are less good than their rivals at enabling us to predict what we shall observe, but that is a conventional decision to reject them, not a “proof” that they are at odds with some objective reality. My 1978 “Trial & Error and the Idea of Progress” was about that.

I knew Popper, and once spent a pleasant day and a half pacing the streets and the beach at St Andrews in his company. He was, I think, the most intelligent person I have met, in a linear, logical, Newtonian way. Hayek was perhaps wiser, bringing a greater breadth of knowledge to his more considered answers. But the two were friends and saw eye to eye on almost everything.