1. One of the 20th century's most influential philosophers of science, Popper is known for his rejection of the classical inductivist views on the scientific method in favour of empirical falsification, and for founding the LSE's Department of Philosophy.
Karl Popper was opposed to the classical justificationist account of knowledge, which he replaced with "the first non-justificational philosophy of criticism in the history of philosophy", namely critical rationalism.
Karl Popper's political thought resides within the camp of Enlightenment rationalism and humanism.
Karl Popper was a dogged opponent of totalitarianism, nationalism, fascism, romanticism, collectivism, and other kinds of reactionary and irrational ideas, and identified modern liberal democracies as the best-to-date embodiment of an open society.
Karl Popper was born in Vienna in 1902 to upper-middle-class parents.
All of Karl Popper's grandparents were assimilated Jews; the Karl Popper family converted to Lutheranism before he was born and so he received a Lutheran baptism.
Karl Popper's father, Simon Siegmund Carl Popper, was a lawyer from Bohemia and a doctor of law at the Vienna University.
Karl Popper's mother, Jenny Schiff, was an accomplished pianist of Silesian and Hungarian descent.
Karl Popper's parents were close friends of Sigmund Freud's sister Rosa Graf.
Karl Popper inherited both the library and the disposition from him.
Karl Popper left school at the age of 16 and attended lectures in mathematics, physics, philosophy, psychology and the history of music as a guest student at the University of Vienna.
In 1919, Karl Popper became attracted by Marxism and subsequently joined the Association of Socialist School Students.
Karl Popper became a member of the Social Democratic Workers' Party of Austria, which was at that time a party that fully adopted Marxism.
Karl Popper worked in street construction for a short time but was unable to cope with the heavy labour.
Karl Popper was dreaming at that time of starting a daycare facility for children, for which he assumed the ability to make furniture might be useful.
Karl Popper completed his examination as an elementary teacher in 1924 and started working at an after-school care club for socially endangered children.
Karl Popper commented that this "was perhaps a cowardly but in a way a right decision".
Karl Popper's dissertation was titled Zur Methodenfrage der Denkpsychologie.
Karl Popper married his colleague Josefine Anna Henninger in 1930.
Karl Popper needed to publish a book to get an academic position in a country that was safe for people of Jewish descent.
In 1937, Karl Popper finally managed to get a position that allowed him to emigrate to New Zealand, where he became lecturer in philosophy at Canterbury University College of the University of New Zealand in Christchurch.
Karl Popper was president of the Aristotelian Society from 1958 to 1959.
Karl Popper retired from academic life in 1969, though he remained intellectually active for the rest of his life.
Karl Popper died of "complications of cancer, pneumonia and kidney failure" in Kenley at the age of 92 on 17 September 1994.
Karl Popper had been working continuously on his philosophy until two weeks before when he suddenly fell terminally ill, writing his last letter two weeks before his death as well.
Karl Popper's estate is managed by his secretary and personal assistant Melitta Mew and her husband Raymond.
Karl Popper's manuscripts went to the Hoover Institution at Stanford University, partly during his lifetime and partly as supplementary material after his death.
The Karl Popper Archives was established within the Klagenfurt University Library, holding Popper's library of approximately 6,000 books, including his precious bibliophilia, as well as hard copies of the original Hoover material and microfilms of the incremental material.
Karl Popper won many awards and honours in his field, including the Lippincott Award of the American Political Science Association, the Sonning Prize, the Otto Hahn Peace Medal of the United Nations Association of Germany in Berlin and fellowships in the Royal Society, British Academy, London School of Economics, King's College London, Darwin College, Cambridge, Austrian Academy of Sciences and Charles University, Prague.
Karl Popper was knighted by Queen Elizabeth II in 1965, and was elected a Fellow of the Royal Society in 1976.
Karl Popper was invested with the insignia of a Member of the Order of the Companions of Honour in 1982.
Karl Popper had at one point joined a socialist association, and for a few months in 1919 considered himself a communist.
Karl Popper then took the view that when it came to sacrificing human lives, one was to think and act with extreme prudence.
Karl Popper suffered from the direct consequences of this failure since events after the Anschluss forced him into permanent exile.
Karl Popper's books defended democratic liberalism as a social and political philosophy.
Karl Popper believed that there was a contrast between the theories of Sigmund Freud and Alfred Adler, which he considered non-scientific, and Albert Einstein's theory of relativity which set off the revolution in physics in the early 20th century.
Karl Popper thought that Einstein's theory, as a theory properly grounded in scientific thought and method, was highly "risky", in the sense that it was possible to deduce consequences from it which differed considerably from those of the then-dominant Newtonian physics; one such prediction, that gravity could deflect light, was verified by Eddington's experiments in 1919.
Karl Popper thus came to the conclusion that they had more in common with primitive myths than with genuine science.
When Karl Popper later tackled the problem of demarcation in the philosophy of science, this conclusion led him to posit that the strength of a scientific theory lies in its both being susceptible to falsification, and not actually being falsified by criticism made of it.
Karl Popper considered that if a theory cannot, in principle, be falsified by criticism, it is not a scientific theory.
Karl Popper coined the term "critical rationalism" to describe his philosophy.
Karl Popper rejected the empiricist view that basic statements are infallible; rather, according to Karl Popper, they are descriptions in relation to a theoretical framework.
Karl 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.
Karl Popper held that scientific theory, and human knowledge generally, is irreducibly conjectural or hypothetical, and is generated by the creative imagination to solve problems that have arisen in specific historico-cultural settings.
For Karl Popper, it is in the interplay between the tentative theories and error elimination that scientific knowledge advances toward greater and greater problems; in a process very much akin to the interplay between genetic variation and natural selection.
Karl Popper wrote extensively against the famous Copenhagen interpretation of quantum mechanics.
Karl Popper strongly disagreed with Niels Bohr's instrumentalism and supported Albert Einstein's scientific realist approach to scientific theories about the universe.
Karl Popper found that Bohr's interpretation introduced subjectivity into physics, claiming later in his life that:.
Karl Popper was talking all the time, allowing practically only one or two words to you and then at once cutting in.
In Of Clocks and Clouds, Karl Popper remarked that he wished he had known of Peirce's work earlier.
Nor is it rational according to Karl Popper to make instead the more complex assumption that the sun will rise until a given day, but will stop doing so the day after, or similar statements with additional conditions.
Karl Popper held that it is the least likely, or most easily falsifiable, or simplest theory that explains known facts that one should rationally prefer.
Karl Popper agreed with David Hume that there is often a psychological belief that the sun will rise tomorrow and that there is no logical justification for the supposition that it will, simply because it always has in the past.
Karl Popper held that rationality is not restricted to the realm of empirical or scientific theories, but that it is merely a special case of the general method of criticism, the method of finding and eliminating contradictions in knowledge without ad-hoc measures.
Karl Popper thinks that no assumption can ever be or needs ever to be justified, so a lack of justification is not a justification for doubt.
Karl Popper's solution was an original contribution in the philosophy of mathematics.
Karl Popper's idea was that a number statement such as "2 apples + 2 apples = 4 apples" can be taken in two senses.
Karl Popper considered historicism to be the theory that history develops inexorably and necessarily according to knowable general laws towards a determinate end.
Karl Popper argued that this view is the principal theoretical presupposition underpinning most forms of authoritarianism and totalitarianism.
Karl Popper argued that historicism is founded upon mistaken assumptions regarding the nature of scientific law and prediction.
The riot had, in fact, been part of a plan by which leaders of the Communist party with connections to Bela Kun tried to take power by a coup; Karl Popper did not know about this at that time.
Karl Popper began to reject Marxist historicism, which he associated with questionable means, and later socialism, which he associated with placing equality before freedom.
Karl Popper said that he was a socialist for "several years", and maintained an interest in egalitarianism, but abandoned it as a whole because socialism was a "beautiful dream", but, just like egalitarianism, it was incompatible with individual liberty.
Karl Popper initially saw totalitarianism as exclusively right-wing in nature, although as early as 1945 in The Open Society he was describing Communist parties as giving a weak opposition to fascism due to shared historicism with fascism.
Over time, primarily in defence of liberal democracy, Karl Popper began to see Soviet-type communism as a form of totalitarianism, and viewed the main issue of the Cold War as not capitalism versus socialism, but democracy versus totalitarianism.
In 1947, Karl Popper co-founded the Mont Pelerin Society, with Friedrich Hayek, Milton Friedman, Ludwig von Mises and others, although he did not fully agree with the think tank's charter and ideology.
Karl Popper criticized what he termed the "conspiracy theory of society", the view that powerful people or groups, godlike in their efficacy, are responsible for purposely bringing about all the ills of society.
Karl Popper wrote of learning in 1935 of the consequences of Tarski's theory, to his intense joy.
Karl Popper identifies Tarski's formulation of the truth conditions of sentences as the introduction of a "metalinguistic predicate" and distinguishes the following cases:.
And, in this way, one theory can be evaluated as more or less true than another on a quantitative basis which, Karl Popper emphasises forcefully, has nothing to do with "subjective probabilities" or other merely "epistemic" considerations.
The simplest mathematical formulation that Karl Popper gives of this concept can be found in the tenth chapter of Conjectures and Refutations.
Karl Popper noted that theism, presented as explaining adaptation, "was worse than an open admission of failure, for it created the impression that an ultimate explanation had been reached".
Karl Popper explained that the difficulty of testing had led some people to describe natural selection as a tautology, and that he too had in the past described the theory as "almost tautological", and had tried to explain how the theory could be untestable and yet of great scientific interest:.
Karl Popper never invented this criterion to give justifiable use of words like science.
Karl Popper had his own sophisticated views on evolution that go much beyond what the frequently-quoted passages say.
In effect, Karl Popper agreed with some points of both creationists and naturalists, but disagreed with both on crucial aspects.
Karl Popper understood the universe as a creative entity that invents new things, including life, but without the necessity of something like a god, especially not one who is pulling strings from behind the curtain.
Karl Popper said that evolution of the genotype must, as the creationists say, work in a goal-directed way but disagreed with their view that it must necessarily be the hand of god that imposes these goals onto the stage of life.
However, although Karl Popper was a body-mind dualist, he did not think that the mind is a substance separate from the body: he thought that mental or psychological properties or aspects of people are distinct from physical ones.
When he gave the second Arthur Holly Compton Memorial Lecture in 1965, Karl Popper revisited the idea of quantum indeterminacy as a source of human freedom.
Karl Popper criticised Compton's idea of amplified quantum events affecting the decision.
Karl Popper was not a religious man in the formal sense of the word.
Karl Popper neither maintained any link with his Jewish ancestry nor was he an observant Lutheran.
For Karl Popper religion was definitely not science, but "because something isn't science does not mean it is meaningless".
Karl Popper helped to establish the philosophy of science as an autonomous discipline within philosophy, both through his own prolific and influential works and through his influence on his contemporaries and students.
In 1946, Karl Popper founded 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.
Karl Popper had long and mutually influential friendships with art historian Ernst Gombrich, biologist Peter Medawar, and neuroscientist John Carew Eccles.
Karl Popper discussed this critique of naive falsificationism in Chapters 3 and 4 of The Logic of Scientific Discovery.
Kuhn argues in The Essential Tension that while Karl Popper was correct that psychoanalysis cannot be considered a science, there are better reasons for drawing that conclusion than those Karl Popper provided.
Karl Popper claimed to have recognised already in the 1934 version of his Logic of Discovery a fact later stressed by Kuhn, "that scientists necessarily develop their ideas within a definite theoretical framework", and to that extent to have anticipated Kuhn's central point about "normal science".
However, Karl Popper criticised what he saw as Kuhn's relativism, this criticism being at the heart of the Kuhn-Karl Popper debate.
Rather than offering a set of instructions that merely need to be followed diligently to achieve science, Karl 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.
In Science Versus Crime, Houck writes that Karl Popper's falsificationism can be questioned logically: it is not clear how Karl Popper would deal with a statement like "for every metal, there is a temperature at which it will melt".
The simplest response to this is that, because Karl 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.
In Transformation der Philosophie, Apel charged Karl Popper with being guilty of, amongst other things, a pragmatic contradiction.
The philosopher Charles Taylor accuses Karl Popper of exploiting his worldwide fame as an epistemologist to diminish the importance of philosophers of the 20th-century continental tradition.
However, Gray's criticism with regards to Einstein is at odds with the fact that Karl Popper frequently used Einstein's theory of general relativity as a case study of how the principle of falsifiability works in practice.