Karl Popper

Sir Karl Raimund Popper (July 28, 1902 – September 17, 1994), was an Austrian-born British philosopher of science and professor at the London School of Economics. He is counted among the most influential philosophers of science of the 20th century, and also wrote extensively on social and political philosophy. Popper is perhaps best known for repudiating the classical observationalist-inductivist account of science; for advancing empirical falsifiability as the criterion for distinguishing scientific theory from non-science; and for his defense of liberal democracy and the principles of social criticism which he took to make the flourishing of the "open society" possible.

Popper's philosophy

Popper coined the term critical rationalism to describe his philosophy. This designation is significant, and indicates his rejection of classical empiricism, and of the observationalist-inductivist account of science that had grown out of it. Popper argued strongly against the latter, holding that scientific theories are universal in nature, and can be tested only indirectly, by references to their implications. He also held that scientific theory, and human knowledge generally, is irreducibly conjectural or hypothetical, and is generated by the creative imagination in order to solve problems that have arisen in specific historico-cultural settings. Logically, no number of positive outcomes at the level of experimental testing can confirm a scientific theory, but a single genuine counter-instance is logically decisive: it shows the theory, from which the implication is derived, to be false. Popper's account of the logical asymmetry between verification and falsification lies at the heart of his philosophy of science. It also inspired him to take falsifiability as his criterion of demarcation between what is and is not genuinely scientific: a theory should be accounted scientific if and only if it is falsifiable. This led him to attack the claims of both psychoanalysis and contemporary Marxism to scientific status, on the basis that the theories enshrined by them are not falsifiable. His scientific work was influenced by his study of Albert Einstein's theory of relativity. Popper's falsificationism resembles Charles Peirce's falliblism. In Of Clocks and Clouds (1966), Popper said he wished he had known of Peirce's work earlier.

Related Topics:
Critical rationalism - Empiricism - Scientific theories - Conjectural - Hypothetical - Imagination - Verification - Falsifiability - Psychoanalysis - Marxism - Albert Einstein - Relativity - Charles Peirce

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In Conjectures and Refutations (1963), Popper sought to explain the apparent progress of scientific knowledge—how it is that our understanding of the universe seems to improve over time. This problem arises from his position that the truth content of our theories, even the best of them, cannot be verified by scientific testing, but can only be falsified. If so, then how is it that the growth of science appears to result in a growth in knowledge? In Popper's view, the advance of scientific knowledge is an evolutionary process characterized by his formula:

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PS_1 ightarrow TT ightarrow EE ightarrow PS_2

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In response to a given problem situation (PS_1), a number of competing conjectures, or tentative theories (TT), are systematically subjected to the most rigorous attempts at falsification possible. This process, error elimination (EE), performs a similar function, for science, that natural selection performs for biological evolution. Theories that better survive the process of refutation are not more true, but rather, more "fit"—in other words, more applicable to the problem situation at hand (PS_1). Consequently, just as a species' "biological fit" does not predict continued survival, neither does rigorous testing protect a scientific theory from refutation in the future. Yet, as it appears that the engine of biological evolution has produced, over time, adaptive traits equipped to deal with more and more complex problems of survival, likewise, the evolution of theories through the scientific method may, in Popper's view, reflect a certain type of progress: toward more and more interesting problems (PS_2). For Popper, it is in the interplay between the tentative theories (conjectures) and error elimination (refutation) that scientific knowledge advances toward greater and greater problems; in a process very much akin to the interplay between genetic variation and natural selection.

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Knowledge, for Popper, was objective, not in the sense that it is objectively true, but rather, that knowledge has an ontological status (i.e.–knowledge as object) independent of the knowing subject (Objective Knowledge: An Evolutionary Approach, 1972). He proposed three worlds (see Popperian cosmology): World One, being the phenomenal world, or the world of direct experience; World Two, being the world of mind, or mental states, ideas, and perceptions; and World Three, being the body of human knowledge expressed in its manifold forms, or the products of the second world made manifest in the materials of the first world (i.e.–books, papers, paintings, symphonies, and all the products of the human mind). World Three, he argued, was the product of individual human beings in exactly the same sense that an animal path is the product of individual animals, and that, as such, has an existence and evolution independent of any individual knowing subjects. The influence of World Three, in his view, on the individual human mind (World Two) is at least as strong as the influence of World One. In other words, the knowledge held by a given individual mind owes at least as much to the total accumulated wealth of human knowledge, made manifest, than to the world of direct experience. As such, the growth of human knowledge could be said to be a function of the independent evolution of World Three. Compare with Memetics. Contemporary philosophers have not embraced Popper's Three World conjecture, due mostly, it seems, to its resemblance to Cartesian dualism.

Related Topics:
Popperian cosmology - Memetics - Cartesian dualism

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In The Open Society and Its Enemies and The Poverty of Historicism, Popper developed a critique of historicism and a defence of the 'Open Society', liberal democracy. Historicism is the theory that history develops inexorably and necessarily according to knowable general laws towards a determinate end. Popper argued that this view is the principal theoretical presupposition underpinning most forms of authoritarianism and totalitarianism. He argued that historicism is founded upon mistaken assumptions regarding the nature of scientific law and prediction. Since the growth of human knowledge is a causal factor in the evolution of human history, and since "no society can predict, scientifically, its own future states of knowledge", it follows, he argued, that there can be no predictive science of human history. For Popper, metaphysical and historical indeterminism go hand in hand.

Related Topics:
The Open Society and Its Enemies - Historicism - Liberal democracy - Authoritarianism - Totalitarianism

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Among his contributions to philosophy is his answer to David Hume's Problem of Induction. Hume stated that just because the sun has risen every day for as long as anyone can remember, doesn't mean that there is any rational reason to believe it will come up tomorrow. There is no rational way to prove that a pattern will continue on just because it has before.

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Popper's reply is characteristic, and ties in with his criterion of falsifiability. He states that while there is no way to prove that the sun will come up, we can theorize that it will. If it does not come up, then it will be disproven, but since right now it seems to be consistent with our theory, the theory is not disproven.

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Thus, Popper's demarcation between science and non-science serves as an answer to an old logical problem as well.

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