Taken from: Wikipedia - Karl Popper
Introduction
Sir Karl Raimund Popper (28 July 1902 – 17 September 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. His father,
Dr. Simon Siegmund Carl Popper, was a doctor of law at the Vienna University and a bibliophile who had 12,000–14,000 volumes
in his personal library. 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 supporter of social liberalism throughout his life.
In 1928 he earned a doctorate in Philosophy 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 for the rest of
his life. 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, Darwin College Cambridge, and Charles University, Prague. Austria awarded him the Grand Decoration of Honour
in Gold.
Popper died in Croydon, UK at the age of 92 on 17 September, 1994. After cremation, his ashes were taken to Vienna and
buried at Lainzer cemetery adjacent to the ORF Centre, where his wife Josefine Anna Henninger - who had died in Austria
several years before - had already been buried.
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 is not genuinely
scientific: a theory should be considered 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. 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 had known of Peirce's work earlier.
In All Life is Problem Solving, 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 characterised by his formula:
PS1 -> TT1 -> EE1 -> PS2.
In response to a given problem situation (PS1), 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 (PS1). 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 (PS2).
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.
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, in Popper's eyes, 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 Vs(a) is the verisimilitude of a, Ctv(a) is a measure of the content of truth of a, and CTf(a) is a measure of the
content of the falsity of a.
Knowledge, for Popper, was objective, both in the sense that it is objectively true (or truthlike), and also in the sense
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 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 (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, 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.
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