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Brief Lives

Sir Karl Popper (1902-1994)

Alistair MacFarlane observes the logic of Karl Popper’s discoveries.

For centuries philosophers have sought to establish how knowledge can be securely founded. Karl Popper’s great insight was that a fundamental asymmetry between verification and falsification undermined this quest. No matter how often evidence is found to verify some theory, only one piece of sound contradictory evidence is sufficient to falsify it. This, in his view, killed Logical Positivism, which was based on an unworkable Principle of Verification.

Popper developed a philosophy of Critical Rationalism, which argued that security for knowledge can only lie in its ability to withstand new evidence and severe, sustained criticism. Critical Rationalism sees new scientific knowledge as gained by a process of conjecture and refutation rather than by inductive reasoning (the process of verifying a general law). If a conjecture can survive all the arguments and evidence which can be adduced against it, that is reason enough to act as if it were true.

Popper’s way of demarcating science from pseudo-science is to say that conjectures which cannot be criticised and tested empirically are useless, and not science. He was deeply influenced in this view by two twentieth century intellectual developments, and the contrast between them. After centuries of believing that Newtonian gravitational theory truly described the astronomical universe, scientists accepted the superiority of Einstein’s new theory of gravitation. A theory once thought to be securely founded was overthrown because it could not account for small discrepancies in the motion of the planet Mercury. Popper also saw how in stark contrast psychoanalytic theories seemed impervious to unwelcome evidence, and so he concluded that psychoanalysis was not a science.

The fierce anti-authoritarianism which Popper brought to the philosophy of science, and his conviction that, since mistakes are unavoidable, energies are better spent on their cure rather than their prevention, informed his work over a wide range of topics. He was, however, much better at advocating the value of criticism than accepting it. Ferocious and tenacious in argument, in a famous encounter he became possibly the only person ever to get the better of Wittgenstein in a face-to-face dispute.

Karl Raimund Popper was born in Vienna, then capital of Austria-Hungary, on 28th July 1902. The son of assimilated Jewish parents who had converted to Lutheranism, he grew up in a comfortable, cultured and tolerant family. His father, Dr Simon Popper, was a successful lawyer, and his mother Jenny (née Schiff) an accomplished musician. They nurtured in him curiosity, a passion for learning (and books), and a lifelong love of music. In the runaway inflation following the Austro-Hungarian defeat in the First World War, Simon Popper lost his life savings. Unwilling to be a burden, Karl left home in the winter of 1919-20. After working as a labourer, then as an apprentice cabinet-maker, he became a fully matriculated student in the University of Vienna in 1922, qualifying to teach in primary schools in 1924. The City of Vienna founded a new Institute of Education, linked to the University, in 1925. There Popper met Hennie, who became his wife, amanuensis, and life-support system.

Working as a primary school teacher, Popper began to teach at the Institute unofficially, to give seminars, and to work towards a PhD, gained in 1928. Qualifying as a teacher of mathematics and physical sciences in 1929, he joined the lower secondary school system and started to develop the ideas which led to his masterpiece Logik der Forschung, published in 1934. It is one of the most important books ever written on the philosophy of science. Despite this, an English translation, The Logic of Scientific Discovery, was not published until 1959.

Popper visited the University of London twice during 1935-36, where his work aroused the sympathetic interest of Professor John Woodger. As the threat of fascist oppression grew in Austria, Woodger suggested to Popper that he answer an advertisement for a post teaching philosophy in Canterbury College of the University of New Zealand. Although they had hoped for a post at Cambridge, Karl and Hennie grasped their chance to escape, arriving in New Zealand in March 1937.

Popper was appalled by the tragedies taking place in Europe, and determined to make his own contribution to the struggle against oppression. He sought to expose and discredit the intellectual origins and claims of totalitarianism, attacking both fascism and communism, since a defeat of Hitler would open the way to a new threat from Stalin. Popper’s principal target was historicism, a perspective which held that the grand sweep of history is ruled by laws of historical development which foretell human destiny. He saw historicist myth-making as inspiring totalitarianism thinking from Plato through Hegel and Marx to Hitler and Stalin. The resulting two books The Poverty of Historicism (published in Economica in 1944/45 and as a book in 1957) and The Open Society and Its Enemies (1945) established his reputation as a political philosopher of great power and originality.

Popper felt isolated in New Zealand, especially by the difficulty of finding publishers. He did however meet and befriend the future Nobel Laureate in medicine, John Eccles, with whom he later collaborated. As the war in Europe was drawing to a close, a wholly unexpected telegram arrived from Friedrich Hayek, the Nobel Prize-winning free market economist, offering him a Readership in the University of London at the London School of Economics. His lifelong friend, Ernst Gombrich the art historian, had persuaded Hayek of the originality and importance of Popper’s work, and publishers were found for the two great books he had written in New Zealand. Popper remained deeply grateful to both men, feeling that they had “saved his life.” In 1949 he was made Professor of Logic and Scientific Method, and remained at LSE until he retired.

With the help and support of the indefatigable Hennie, Popper sought to develop The Logic of Scientific Discovery into a comprehensive masterwork, by producing a series of Postscripts to it. This monumental effort started in 1958 and continued for over twenty years. But his health deteriorated, and in 1960 his eyesight began to fail. Returning to Vienna, he underwent operations for detached retinas on both eyes. Work on the Postscripts had to be abandoned. It restarted, but had to be again set aside in 1969, and the piecemeal production of this huge enterprise was not completed until the 1980s. There finally emerged the three volumes which together comprise the Postscripts: The Open Universe (1982), Quantum Theory and the Schism in Physics (1982), and Realism and the Aim of Science (1983). Together with Conjectures and Refutations (1963) and Objective Knowledge (1972), these works constitute a coherent, compelling contribution to the philosophy of science.

Popper’s indefatigable intellectual energy, his constant curiosity embracing a wide range of topics, and his willingness to tackle big philosophical problems, led him to his last major undertaking. What he called ‘the philosophy of my old age’ started from an essay entitled ‘Of Clouds and Clocks’ (part of Objective Knowledge), in which he directly confronted physical determinism – the doctrine that there is no free will because the brain obeys determinate physical laws. He complemented Descartes’ Problem (how do mind and body interact ?) with what he called Compton’s Problem (how can the physical world be influenced by abstract entities?). Popper advanced a hypothesis that mind, language and consciousness form an evolved hierarchy which allows sentient organisms the freedom to pose and find solutions to the problems of interacting with their environment. This led him to develop a picture of three distinct but interacting domains – the physical, the mental, and the world of the products of human mental activity. At Eccles’ suggestion, he called them Worlds 1, 2 and 3.

This theory of three distinct, interacting domains has had detractors (by what mechanisms do they interact?). Nevertheless, it attacked a major philosophical problem, and can be re-formulated in a less extravagant form, in terms of three interrelated types of knowledge – subjective, objective and inter-subjective.

In early 1977, Hennie was found to have a malignant tumour. This had so much worsened by 1985 that the Poppers returned to Vienna, where Hennie died in November of that year. Although both had resumed Austrian nationality, and despite efforts to make him stay in Austria, Popper returned to England in 1987. Working to the end, he died after an operation on 17th September 1994. After cremation, his ashes were buried in his wife’s grave in the Lanzer Friedof cemetery in Vienna, of which city he had been made an honorary citizen in 1992. His final return to Vienna was fitting, as he embodied so many of that city’s great intellectual traditions. Britain, his adopted country, also recognised his outstanding achievements, making him a knight, a Companion of Honour, and one of the very few people to have been elected to both the British Academy (in 1958) and the Royal Society (in 1976).

Sir Karl Popper was a realist, a rationalist, an objectivist and an indeterminist, with a high regard for common sense and imagination. Humanists applauded his scholarship and his passionate advocacy of freedom; scientists valued his grasp of science and his insight into the scientific process; and both admired the power, clarity and coherence of his arguments.

Sir Alistair MacFarlane is a former Vice-President of the Royal Society and a retired university Vice-Chancellor.

The Logic of Scientific Discovery

In the early 20th century, a group of Austrian thinkers who became known as the Vienna Circle developed the idea that only statements which could in principle be verified by observed facts were meaningful; all other statements, including those about religion and ethics, were just useless metaphysics. This approach, known as Logical Positivism, was introduced to the English-speaking world by A.J. Ayer in his book Language, Truth and Logic.

Then Karl Popper pointed out in his book The Logic of Scientific Discovery that while no amount of evidence supporting a theory can ever prove it beyond all doubt, a single piece of evidence contradicting a theory is enough to bury it. He therefore turned Logical Positivism on its head, saying that the criterion of a meaningful statement was not whether it could in principle be verified, but whether it could in principle be falsified.