Karl Popper, an eminent philosopher and social theorist, was born in Vienna, but subsequently became a British subject. When young, Popper was intellectually precocious and had a keen interest in science, psychology, and, subsequently, philosophy. He became interested in socialism when in his mid‐​teens, and he briefly flirted with Marxism, working as a volunteer in the offices of the Austrian Communist Party. He soon abandoned his early socialist sympathies and became immersed in more purely philosophical questions, during which he developed a particular interest in what characterized scientific knowledge. Popper was influenced by the psychologists Karl Buehler and Otto Selz and by a distinctive kind of Kantianism favored by the German philosopher Leonard Nelson. His interest in science in part reflected the concerns of the logical positivists of the Vienna Circle.

Popper’s theory of knowledge is distinctive in several respects. He emphasized the criterion of falsification as the distinctive mark of science (although he was prepared to accept certain unfalsifiable ideas as having influenced the development of science). More generally, he developed a unique approach to epistemology, in which he rejected induction as the sole criterion for determining the value of scientific statements and in its place underscored the importance of such statements to resolve problems and survive tests and criticism. For Popper, the scientific character of a work depended not solely on its logical character, but also on how its proponents dealt with it (e.g., how they reacted to criticism). This schema added up to a strongly antiauthoritarian view of knowledge that placed a premium on bold ideas and held even the most venerable expert open to challenge. Popper was not a relativist, but he emphasized the fallibility of our knowledge. He was a realist, with a firm belief in the existence of an external world and in the legitimacy of the attempt to undercover its truths.

In addition to his work in the philosophy of science, Popper developed several unique insights of a more general philosophical nature. These insights offered a systematic view of mankind and of the universe in which we live. Popper believed that the world was objectively indeterministic, and he developed a metaphysic of indeterministic propensities or dispositions. Although he concluded that attempts at scientific reduction were methodologically fruitful, he was skeptical about the success of most such reductions and, indeed, embraced a form of mind–body interaction. (Popper favored a biological approach to psychology and to the mind, by which he conceived the mind as playing a significant role as an intermediary between the physical world and the realm of abstract ideas.) He had a strong interest in science, and his philosophical ideas led him to undertake work on scientific issues, such as offering arguments for a realist understanding of such abstruse concepts as the arrow of time and the nature of quantum theory.

Popper also is well known for his writings on social philosophy. His books Open Society and Its Enemies and The Poverty of Historicism, both written during the Second World War, were powerful attacks on Plato, Marx, and their arguments in favor of historical inevitability as enemies of an open society. The open society that Popper favored was characterized by ethical individualism—in opposition to the moral collectivism of his day—and was influenced by Kantian ideas about the significance of intersubjective criticism. Popper supported a political regime under which government was charged with the protection of the freedom of the individual—not only in the sense favored by classical liberals, but also a protection that extended to being free from economic exploitation. He favored a policy of piecemeal social engineering, in which governmental initiatives were to address problems that were responsible for suffering and injustice about which there was general agreement. Popper noted that such actions would have unintended consequences and that consequently governments should be open to critical feedback from citizens regarding the results of these actions.

When living in Vienna, Popper was a socialist, and The Open Society reflected its radical character. Nevertheless, both he and F. A. Hayek were struck by strong similarities between some of its features and Hayek’s Road to Serfdom. In later years, Popper’s views became closer to those of Hayek, and he became convinced that the political pursuit of equality was a danger to liberty. However, occasional comments about the burdens of taxation notwithstanding, Popper’s political views did not change substantially, and he consistently saw liberty as ultimately depending on government intervention. Although he recognized free markets as useful, he did not share Hayek’s optimism about the self‐​coordinating characteristics of a market‐​based social order.

Further Readings

Hacohen, Malachi. Karl Popper—The Formative Years, 1902–1945: Politics and Philosophy in Interwar Vienna. Cambridge: Cambridge University Press, 2000.

Miller, David. Critical Rationalism: A Restatement and Defence. Chicago: Open Court, 1994.

Popper, Karl. The Open Society and Its Enemies. 2 vols. London: Routledge, 1945.

———. The Poverty of Historicism. 2nd ed. London: Routledge, 1961.

Schilpp, P. A., ed. The Philosophy of Karl Popper. 2 vols. La Salle, IL: Open Court Press, 1974.

Shearmur, Jeremy. Political Thought of Karl Popper. London & New York: Routledge, 1996.

Originally published