Popper, Sir Karl Raimund

Popper, Sir Karl Raimund (1902-1994), Austrian-born British philosopher of science, known for his theory of scientific method and for his criticism of historical determinism. He was born in Vienna and received a doctorate from the University of Vienna in 1928. Although not a member of the so-called Vienna school of philosophy (see Positivism), Popper sympathized with their scientific attitude, but was critical of certain of their beliefs. From 1937 to 1945 he taught at Canterbury College, University of New Zealand, and then at the London School of Economics. He died on September 17, 1994.

Popper’s most significant contribution to the philosophy of science was his characterization of the scientific method. In The Logic of Scientific Discovery (1934; trans. 1959), he criticized the prevailing view that science is fundamentally inductive in nature—that scientists discover and prove scientific theories by inductive inference from observation and experiment. Popper declared that this inductive method is a myth. Scientists do not discover theories from observations, but propose hypotheses to account for observations. These hypotheses may be tested, by deducing predictions from them and then making observations or experiments to see if these predictions are true. If the appropriate observations or experiments show that some prediction is false, then the hypothesis is refuted. If a hypothesis survives efforts to falsify it, then it is corroborated and may be tentatively accepted. But in this hypothetico-deductive model of science, no theory can be conclusively established as true. The criterion that demarcates scientific from unscientific theories is not verifiability by observation, but falsifiability by observation. However, Popper objected to the positivist view that non-science is the same as non-sense. Neither the positivist verifiability theory of meaning, nor some falsifiability theory of meaning, is acceptable. Non-science or metaphysics is not meaningless. On the contrary, metaphysical ideas have had enormous influence on the development of science. Popper’s example was early Greek atomism, a metaphysical theory that eventually gave rise to scientific, testable atomic theories in the 19th century.

Although Popper claimed that no scientific theory can be proved or established as true, he nonetheless insisted that the aim of scientific inquiry is truth. He attacked the view that science aims, not for truth, but only for more or less useful instruments for predicting phenomena. Popper defended scientific realism and opposed antirealism (which he called “instrumentalism”). He also opposed antirealist or idealist views in philosophy, ranging from the theory of sense-data (which says that we observe or experience only “sense-data” in our minds rather than objects in the world), to the idealism of George Berkeley (which says that all that exists are minds and their sense-data), and finally the transcendental idealism of Immanuel Kant (which says that science deals only with a constructed “world of experience” rather than some inaccessible “real” world).

Popper also detected and opposed what he saw as idealist or subjectivist views in the interpretation of scientific theories. These included the subjectivist interpretation of statements of probability in science as expressions of our ignorance. Popper developed an objective, propensity interpretation of probability, according to which statements of probability describe objective chances or propensities in nature. If the fundamental laws of physics are probabilistic, then it follows (according to Popper) that nature is indeterministic: fundamental probabilistic laws do not merely reflect our ignorance of a deterministic world. Similarly, Popper opposed the prevailing Copenhagen interpretation of quantum mechanics, according to which physical systems do not exist in well-defined states until some measurement is made upon them.

In The Open Society and Its Enemies (1945), Popper defended democracy and advanced objections to the totalitarian implications of the political theories of Plato and Karl Marx. He argued that the central question of political philosophy is not “Who should rule?”, but rather “How can we get rid of unsatisfactory rulers?”. He defended democracy as the best answer to the second question, not the first. If we are to get rid of unsatisfactory rulers through democratic processes, we need to be able to criticize them freely and that requires the institution of an open rather than a closed society. As for Plato and Marx, he criticized their “historicist” view that discoverable laws of the development of history render its future course inevitable and thus predictable. In The Poverty of Historicism (1957), Popper presented the following refutation of historicism: the future course of human history is strongly influenced by the growth of human knowledge; we cannot predict the growth of knowledge (we cannot anticipate today what we shall know only tomorrow); therefore, we cannot predict the future course of human history.