Everything about Karl Popper totally explained
Sir Karl Raimund Popper (
July 28,
1902 –
September 17,
1994) was an
Austrian and
British philosopher and a 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 known for repudiating the classical observationalist/
inductivist account of
scientific method by advancing empirical
falsification instead; for his opposition to the classical
justificationist account of knowledge which he replaced with
critical rationalism, "the first
non justificational philosophy of criticism in the history of philosophy" and for his vigorous defense of
liberal democracy and the principles of
social criticism which he took to make the flourishing of the "
open society" possible.
Life
Karl Popper was born in
Vienna (then in
Austria-Hungary) in
1902 to
middle-class parents of
Jewish origins, both of whom had converted to
Christianity. Popper received a
Lutheran upbringing and was educated at the
University of Vienna. Popper inherited from him both the library and the disposition.
In
1919 he became attracted by
Marxism and subsequently joined the Association of Socialist School Students and also became a member of the
Social Democratic Party of Austria, which was at that time a party that fully adopted the marxist ideology. He soon became disillusioned by the philosophical restraints imposed by the
historical materialism of Marx, abandoned the ideology and remained a passive supporter of
social liberalism throughout his life.
In
1928 he earned a PhD in Psychology and taught secondary school from 1930 to 1936.
He published his first book,
Logik der Forschung (
The Logic of Scientific Discovery), in
1934. Here, he criticised
psychologism,
naturalism,
inductionism, and
logical positivism, and put forth his theory of potential
falsifiability as the criterion demarcating science from non-science.
In
1937, the rise of
Nazism and the threat of the
Anschluss led Popper to emigrate to
New Zealand, where he became lecturer in philosophy at
Canterbury University College New Zealand (at
Christchurch). In
1946, he moved to
England to
become reader in
logic and
scientific method at the
London School of Economics, where he was appointed professor in
1949. He was president of the
Aristotelian Society from 1958 to 1959. He was
knighted by
Queen Elizabeth II in
1965, and was elected a Fellow of the
Royal Society in
1976. He retired from academic life in
1969, though he remained intellectually active until his death in
1994. He was invested with the Insignia of a
Companion of Honour in
1982. Popper was a member of the
Academy of Humanism and described himself as an
agnostic, showing respect for the moral teachings of Judaism and Christianity.
Popper won many awards and honours in his field, including the Lippincott Award of the
American Political Science Association, the
Sonning Prize, and fellowships in the
Royal Society,
British Academy,
London School of Economics,
King's College London, and
Darwin College Cambridge. Austria awarded him the Grand Decoration of Honour in Gold. He died in 1994. After cremation, Popper's ashes were taken to
Vienna and buried at Lainz cemetery adjacent to the
ORF Centre, where his wife Josefine Anna Henninger - who had died in Austria several years before - had already been buried.
Popper's philosophy
Philosophy of Science
Popper coined the term
critical rationalism to describe his philosophy. The term 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 abstract in nature, and can be tested only indirectly, by reference 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 counterexample 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
falsifiability 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 isn't genuinely scientific: a theory should be considered scientific if and only if it's 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. Popper also wrote extensively against the famous
Copenhagen interpretation of
quantum mechanics. He strongly disagreed with
Niels Bohr's
instrumentalism and supported
Albert Einstein's
realist approach to
scientific theories about the universe. Popper's falsifiability resembles
Charles Peirce's
fallibilism. In
Of Clocks and Clouds (1966), Popper remarked that he wished he'd known of Peirce's work earlier.
In
All Life is Problem Solving, Popper sought to explain the apparent progress of scientific knowledge—how it's 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, can't 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 characterised by his formula:
In response to a given problem situation (
), a number of competing conjectures, or tentative theories (
), are systematically subjected to the most rigorous attempts at falsification possible. This process, error elimination (
), 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 (
). Consequently, just as a species' "biological fit" doesn't 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 (
). For Popper, it's 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.
Where does "truth" fit into all this? As early as 1934 Popper wrote of the search for truth as "
one of the strongest motives for scientific discovery." Still, he describes in
Objective Knowledge (1972) early concerns about the much-criticised notion of
truth as correspondence. Then came the
semantic theory of truth formulated by the logician
Alfred Tarski and published in 1933. Popper writes of learning in 1935 of the consequences of Tarski's theory, to his intense joy. The theory met critical objections to
truth as correspondence and thereby rehabilitated it. The theory also seemed to Popper to support
metaphysical realism and the
regulative idea of a search for truth.
According to this theory, the conditions for the truth of a sentence as well as the sentences themselves are part of a
metalanguage. So, for example, the sentence "Snow is white" is true if and only if snow is white. Although many philosophers have interpreted, and continue to interpret, Tarski's theory as a
deflationary theory, Popper refers to it as a theory in which "is true" is replaced with "
corresponds to the facts." He bases this interpretation on the fact that examples such as the one described above refer to two things: assertions and
the facts to which they refer. He identifies Tarski's formulation of the truth conditions of sentences as the introduction of a "metalinguistic predicate" and distinguishes the following cases:
- "John called" is true.
- "It is true that John called."
The first case belongs to the metalanguage whereas the second is more likely to belong to the object language. Hence, "it is true that" possesses the logical status of a redundancy. "Is true", on the other hand, is a predicate necessary for making general observations such as "John was telling the truth about Phillip."
Upon this basis, along with that of the logical content of assertions (where logical content is inversely proportional to probability), Popper went on to develop his important notion of
verisimilitude or "truthlikeness".
The intuitive idea behind verisimilitude is that the assertions or hypotheses of scientific theories can be objectively measured with respect to the amount of truth and falsity that they imply. And, in this way, one theory can be evaluated as more or less true than another on a quantitative basis which, Popper emphasizes forcefully, has nothing to do with "subjective probabilities" or other merely "epistemic" considerations.
The simplest mathematical formulation that Popper gives of this concept can be found in the tenth chapter of
Conjectures and Refutations.. Here he defines it as:
where
is the verisimilitude of
a,
is a measure of the content of truth of
a, and
is a measure of the content of the falsity of
a.
Knowledge, for Popper, was
objective, both in the sense that it's objectively true (or truthlike), and also in the sense that knowledge has an ontological status (for example, 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 physical world, or physical states; 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 (for example–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, as 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. Many contemporary philosophers have not embraced Popper's Three World conjecture, due mostly, it seems, to its resemblance to
Cartesian dualism.
Political philosophy
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'. 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.
Problem of Induction
Among his contributions to philosophy is his attempt to answer the philosophical
problem of induction. The problem, in basic terms, can be understood by example: given that the sun has risen every day for as long as anyone can remember, what is the rational proof that it'll rise tomorrow? How can one rationally prove that past events will continue to repeat in the future, just because they've repeated in the past? Popper's reply is characteristic, and ties in with his criterion of falsifiability. He states that while there's no way to prove that the sun will rise, we can formulate a theory that every day the sun will rise—if it doesn't rise on some particular day, our theory will be disproved, but at present it's confirmed. Since it's a very well-tested theory, we've every right to believe that it accurately represents reality, so far as we know.
This may be a true description of the pragmatic approach to knowledge adopted by the scientific method, but it doesn't in itself address the philosophical problem. As
Stephen Hawking explains, "No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result won't contradict the theory." It may be pragmatically useful to accept a well-tested theory as true until it's falsified, but this doesn't solve the philosophical problem of induction. As
Bertrand Russell put it, "the general principles of science . . . are believed because mankind have found innumerable instances of their truth and no instances of their falsehood. But this affords no evidence for their truth in the future, unless the inductive principle is assumed." In essence, Popper addressed justification for
belief ("
why do you believe") that the sun will rise tomorrow, not justification for the
fact ("
how do you know") that it will, which is the crux of the philosophical problem. Said another way, Popper addressed the psychological
causes of our belief in the validity of induction without trying to provide logical
reasons for it. In this way, he provided a psychological account of the use of induction, but left the philosophical ground of induction as a valid mode of knowledge unaccounted for.
Influence
By all accounts, Popper has played a vital role in establishing the
philosophy of science as a vigorous, autonomous discipline within
analytic philosophy, through his own prolific and influential works, and also through his influence on his own contemporaries and students. Popper founded in 1946 the Department of Philosophy, Logic and Scientific Method at the
London School of Economics and there lectured and influenced both
Imre Lakatos and
Paul Feyerabend, two of the foremost philosophers of science in the next generation of philosophy of science. (Lakatos significantly modified Popper's position, and Feyerabend repudiated it entirely, but the work of both is deeply influenced by Popper and engaged with many of the problems that Popper set.)
While there's some dispute as to the matter of influence, Popper had a long-standing and close friendship with economist
Friedrich Hayek, who was also brought to the
London School of Economics from Vienna. Each found support and similarities in each other's work, citing each other often, though not without qualification. In a letter to Hayek in 1944, Popper stated, "I think I've learnt more from you than from any other living thinker, except perhaps
Alfred Tarski." (See Hacohen, 2000). Popper dedicated his
Conjectures and Refutations to Hayek. For his part, Hayek dedicated a collection of papers,
Studies in Philosophy, Politics, and Economics, to Popper, and in 1982 said, "...ever since his
Logik der Forschung first came out in 1934, I've been a complete adherent to his general theory of methodology." (See Weimer and Palermo, 1982).
Popper also had long and mutually influential friendships with art historian
Ernst Gombrich, biologist
Peter Medawar, and neuro-scientist
John Carew Eccles.
Popper's influence, both through his work in philosophy of science and through his political philosophy, has also extended beyond the academy. Among Popper's students and advocates at the
London School of Economics is the multibillionaire investor
George Soros, who says his investment strategies are modelled on Popper's understanding of the advancement of knowledge through
falsification. Among Soros's
philanthropic foundations is the
Open Society Institute, a think-tank named in honour of Popper's
The Open Society and Its Enemies, which Soros founded to advance the Popperian defense of the
open society against
authoritarianism and
totalitarianism.
Popperian philosophy also inspired the creation of
Taking Children Seriously, a movement arguing that children and adults should try to resolve their differences without coercion.
Critics
Criticism of his philosophy of science
Most criticisms of Popper's philosophy are of the falsification, or error elimination, element in his account of problem solving. In interpreting these, it's important to bear in mind the aims of his idea. It is intended as an ideal, practical method of effective human problem solving; as such, the current conclusions of science are stronger than pseudo-sciences or non-sciences, insofar as they've survived this particularly vigorous selection method. He doesn't argue that any such conclusions are therefore true, or that this describes the actual methods of any particular scientist.
Rather, it's a recommended ideal method that, if enacted by a system or community, will over time lead to slow but steady progress of a sort (relative to how well the system or community enacts the method). It has been suggested that Popper's ideas are often mistaken for a hard logical account of truth because of the historical co-incidence of their appearing at the same time as
logical positivism, the followers of which mistook his aims for their own (Brian Magee 1973: Popper (Modern Masters series).
The
Quine-Duhem thesis argues that it's impossible to test a single hypothesis on its own, since each one comes as part of an environment of theories. Thus we can only say that the whole package of relevant theories has been collectively falsified, but can't conclusively say which element of the package must be replaced. An example of this is given by the discovery of the planet
Neptune: when the motion of
Uranus was found not to match the predictions of Newton's laws, the theory "There are seven planets in the solar system" was rejected, and not Newton's laws themselves. Popper discussed this critique of
naïve falsificationism in Chapters 3 & 4 of
The Logic of Scientific Discovery. For Popper, theories are accepted or rejected via a sort of 'natural selection'. Theories that say more about the way things appear are to be preferred over those that do not; the more generally applicable a theory is, the greater its value. Thus Newton’s laws, with their wide general application, are to be preferred over the much more specific “the solar system has seven planets”.
Thomas Kuhn’s influential book
The Structure of Scientific Revolutions argued that scientists work in a series of
paradigms, and found little evidence of scientists actually following a falsificationist methodology. Popper's student
Imre Lakatos attempted to reconcile Kuhn’s work with
falsificationism by arguing that science progresses by the falsification of
research programs rather than the more specific
universal statements of naïve falsificationism. Another of Popper’s students
Paul Feyerabend ultimately rejected any prescriptive methodology, and argued that the only universal method characterizing scientific progress was
anything goes.
Popper seems to have anticipated Kuhn's observations. In his collection
Conjectures and Refutations: The Growth of Scientific Knowledge (Harper & Row, 1963), Popper writes, "Science must begin with myths, and with the criticism of myths; neither with the collection of observations, nor with the invention of experiments, but with the critical discussion of myths, and of magical techniques and practices. The scientific tradition is distinguished from the pre-scientific tradition in having two layers. Like the latter, it passes on its theories; but it also passes on a critical attitude towards them. The theories are passed on, not as dogmas, but rather with the challenge to discuss them and improve upon them."
Another objection is that it isn't always possible to demonstrate falsehood definitively, especially if one is using
statistical criteria to evaluate a
null hypothesis. More generally, it isn't always clear that if evidence contradicts a hypothesis that this is a sign of flaws in the hypothesis rather than of flaws in the evidence. However, this is a misunderstanding of what Popper's philosophy of science sets out to do. Rather than proffering a set of instructions that merely need to be followed diligently to achieve science, Popper makes it clear in
The Logic of Scientific Discovery that his belief is that the resolution of conflicts between hypotheses and observations can only be a matter of the collective judgment of scientists, in each individual case.
Popper's falsificationism can be questioned logically, by asking about statements such as "There are
black holes", which can't be falsified by any possible observation, yet which seems to be a legitimately scientific claim. Similarly, it's not clear how Popper would deal with a statement like "for every metal, there's a temperature at which it'll melt", which can neither be confirmed nor falsified by any possible observation, yet which seems to be a valid scientific hypothesis. These examples were pointed out by
Carl Gustav Hempel. Hempel came to acknowledge that Logical Positivism's verificationism was untenable, but argued that falsificationism was equally untenable on logical grounds alone. The simplest response to this is that, because Popper describes how theories attain, maintain and lose scientific status, individual consequences of currently accepted scientific theories are scientific in the sense of being part of tentative scientific knowledge, and both of Hempel's examples fall under this category. For instance,
atomic theory implies that all metals melt at some temperature.
Other criticisms
Other critics seek to vindicate the claims of
historicism or
holism to intellectual respectability, or
psychoanalysis or
Marxism to scientific status. It has been argued that Popper's student
Imre Lakatos, for example, transformed Popper's philosophy using historicist and updated Hegelian historiographic ideas.
Charles Taylor accuses Popper of exploiting his worldwide fame as an epistemologist to diminish the importance of philosophers of the 20th century
continental tradition. According to Taylor, Popper's criticisms are completely baseless, but they're received with an attention and respect that Popper's "intrinsic worth hardly merits". William W. Bartley defended Popper against such allegations: "Sir Karl Popper isn't really a participant in the contemporary professional philosophical dialogue; quite the contrary, he's ruined that dialogue. If he's on the right track, then the majority of professional philosophers the world over has wasted or is wasting their intellectual careers. The gulf between Popper's way of doing philosophy and that of the bulk of professional philosophers is as great as that between astronomy and astrology."
In
2004 philosopher and
psychologist Michel ter Hark (
Groningen,
The Netherlands) published a book, called
Popper, Otto Selz and the rise of evolutionary epistemology, ISBN 0521830745, in which he claimed that Popper took some of his ideas from his tutor, the German-Jewish psychologist
Otto Selz. Selz himself never published his ideas, partly because of the rise of
Nazism which forced him to quit his work in
1933, and the prohibition of referring to Selz' work.
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