Karl Popper

Karl Popper

Overview
Sir Karl Raimund Popper, CH
Order of the Companions of Honour
The Order of the Companions of Honour is an order of the Commonwealth realms. It was founded by King George V in June 1917, as a reward for outstanding achievements in the arts, literature, music, science, politics, industry or religion....

 FRS FBA (28 July 1902 – 17 September 1994) was an Austro-British philosopher and a professor at the London School of Economics
London School of Economics
The London School of Economics and Political Science is a public research university specialised in the social sciences located in London, United Kingdom, and a constituent college of the federal University of London...

. He is regarded as one of the greatest philosophers of science
Philosophy of science
The philosophy of science is concerned with the assumptions, foundations, methods and implications of science. It is also concerned with the use and merit of science and sometimes overlaps metaphysics and epistemology by exploring whether scientific results are actually a study of truth...

 of the 20th century; he also wrote extensively on social and political philosophy.

Popper is known for his attempt to repudiate the classical observationalist / inductivist
Inductivism
In the philosophy of science inductivism exists both in a classical naive version, which has been highly influential, and in various more sophisticated versions...

 form of scientific method
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...

 in favour of empirical falsification
Falsifiability
Falsifiability or refutability of an assertion, hypothesis or theory is the logical possibility that it can be contradicted by an observation or the outcome of a physical experiment...

.
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Quotations

You can choose whatever name you like for the two types of government. I personally call the type of government which can be removed without violence "democracy", and the other "tyranny".

As quoted in Freedom: A New Analysis (1954) by Maurice William Cranston, p. 112

Piecemeal social engineering resembles physical engineering in regarding the ends as beyond the province of technology. (All that technology may say about ends is whether or not they are compatible with each other or realizable.)

The Poverty of Historicism (1957) Ch. 22 The Unholy Alliance with Utopianism

If we are uncritical we shall always find what we want: we shall look for, and find, confirmations, and we shall look away from, and not see, whatever might be dangerous to our pet theories. In this way it is only too easy to obtain what appears to be overwhelming evidence in favor of a theory which, if approached critically, would have been refuted.

The Poverty of Historicism (1957) Ch. 29 The Unity of Method

Whenever a theory appears to you as the only possible one, take this as a sign that you have neither understood the theory nor the problem which it was intended to solve.

Objective Knowledge: An Evolutionary Approach (1972)

There is an almost universal tendency, perhaps an inborn tendency, to suspect the good faith of a man who holds opinions that differ from our own opinions. … It obviously endangers the freedom and the objectivity of our discussion if we attack a person instead of attacking an opinion or, more precisely, a theory.

"The Importance of Critical Discussion" in On the Barricades: Religion and Free Inquiry in Conflict (1989) by Robert Basil

Science may be described as the art of systematic over-simplification — the art of discerning what we may with advantage omit.

The Open Universe : An Argument for Indeterminism (1992), p. 44

I think so badly of philosophy that I don't like to talk about it. ... I do not want to say anything bad about my dear colleagues, but the profession of teacher of philosophy is a ridiculous one. We don't need a thousand of trained, and badly trained, philosophers — it is very silly. Actually most of them have nothing to say.

As quoted in "At 90, and Still Dynamic : Revisiting Sir Karl Popper and Attending His Birthday Party" by Eugene Yue-Ching Ho, in Intellectus 23 (Jul-Sep 1992)
Encyclopedia
Sir Karl Raimund Popper, CH
Order of the Companions of Honour
The Order of the Companions of Honour is an order of the Commonwealth realms. It was founded by King George V in June 1917, as a reward for outstanding achievements in the arts, literature, music, science, politics, industry or religion....

 FRS FBA (28 July 1902 – 17 September 1994) was an Austro-British philosopher and a professor at the London School of Economics
London School of Economics
The London School of Economics and Political Science is a public research university specialised in the social sciences located in London, United Kingdom, and a constituent college of the federal University of London...

. He is regarded as one of the greatest philosophers of science
Philosophy of science
The philosophy of science is concerned with the assumptions, foundations, methods and implications of science. It is also concerned with the use and merit of science and sometimes overlaps metaphysics and epistemology by exploring whether scientific results are actually a study of truth...

 of the 20th century; he also wrote extensively on social and political philosophy.

Popper is known for his attempt to repudiate the classical observationalist / inductivist
Inductivism
In the philosophy of science inductivism exists both in a classical naive version, which has been highly influential, and in various more sophisticated versions...

 form of scientific method
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...

 in favour of empirical falsification
Falsifiability
Falsifiability or refutability of an assertion, hypothesis or theory is the logical possibility that it can be contradicted by an observation or the outcome of a physical experiment...

. He is also known for his opposition to the classical justificationist account of knowledge which he replaced with critical rationalism
Critical rationalism
Critical rationalism is an epistemological philosophy advanced by Karl Popper. Popper wrote about critical rationalism in his works, The Open Society and its Enemies Volume 2, and Conjectures and Refutations.- Criticism, not support :...

, "the first non justificational philosophy of criticism in the history of philosophy". As well, he is known for his vigorous defense of liberal democracy
Liberal democracy
Liberal democracy, also known as constitutional democracy, is a common form of representative democracy. According to the principles of liberal democracy, elections should be free and fair, and the political process should be competitive...

 and the principles of social criticism
Social criticism
The term social criticism locates the reasons for malicious conditions of the society in flawed social structures. People adhering to a social critics aim at practical solutions by specific measures, often consensual reform but sometimes also by powerful revolution.- European roots :Religious...

 that he came to believe made a flourishing "open society
Open society
The open society is a concept originally developed by philosopher Henri Bergson and then by Austrian and British philosopher Karl Popper. In open societies, government is purported to be responsive and tolerant, and political mechanisms are said to be transparent and flexible...

" possible.

Life


Karl Popper was born in Vienna
Vienna
Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...

 (then in Austria-Hungary
Austria-Hungary
Austria-Hungary , more formally known as the Kingdoms and Lands Represented in the Imperial Council and the Lands of the Holy Hungarian Crown of Saint Stephen, was a constitutional monarchic union between the crowns of the Austrian Empire and the Kingdom of Hungary in...

) in 1902, to upper middle-class parents. All of Karl Popper's grandparents were Jewish, but the Popper family converted to Lutheranism
Lutheranism
Lutheranism is a major branch of Western Christianity that identifies with the theology of Martin Luther, a German reformer. Luther's efforts to reform the theology and practice of the church launched the Protestant Reformation...

 before Karl was born. Karl's father Simon Siegmund Carl Popper was a lawyer from Bohemia
Bohemia
Bohemia is a historical region in central Europe, occupying the western two-thirds of the traditional Czech Lands. It is located in the contemporary Czech Republic with its capital in Prague...

, and mother Jenny Schiff was of Silesian
Silesians
Silesians , are the inhabitants of Silesia in Poland, Germany and the Czech Republic. A small diaspora community also exists in Karnes County, Texas in the USA....

 and Hungarian descent. After establishing themselves in Vienna, the Poppers made a rapid social climb in Viennese society: Simon Siegmund Carl became a legal partner of Vienna's liberal mayor Raimond Grübl and, after his death in 1898, took over the firm (Karl received his middle name from the mayor).

Popper received a Lutheran upbringing and was educated at the University of Vienna
University of Vienna
The University of Vienna is a public university located in Vienna, Austria. It was founded by Duke Rudolph IV in 1365 and is the oldest university in the German-speaking world...

. His father 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 both the library and the disposition from him.

In 1919, Popper became attracted by Marxism
Marxism
Marxism is an economic and sociopolitical worldview and method of socioeconomic inquiry that centers upon a materialist interpretation of history, a dialectical view of social change, and an analysis and critique of the development of capitalism. Marxism was pioneered in the early to mid 19th...

 and subsequently joined the Association of Socialist School Students. He also became a member of the Social Democratic Workers' Party of Austria
Social Democratic Party of Austria
The Social Democratic Party of Austria is one of the oldest political parties in Austria. The SPÖ is one of the two major parties in Austria, and has ties to trade unions and the Austrian Chamber of Labour. The SPÖ is among the few mainstream European social-democratic parties that have preserved...

, which was at that time a party that fully adopted the Marxist ideology. After the June 15, 1919 street battle in the Hörlgasse, when police shot eight of his unarmed party comrades, he became disillusioned by what he saw to be the pseudo-scientific historical materialism
Historical materialism
Historical materialism is a methodological approach to the study of society, economics, and history, first articulated by Karl Marx as "the materialist conception of history". Historical materialism looks for the causes of developments and changes in human society in the means by which humans...

 of Marx, abandoned the ideology and remained a supporter of social liberalism
Social liberalism
Social liberalism is the belief that liberalism should include social justice. It differs from classical liberalism in that it believes the legitimate role of the state includes addressing economic and social issues such as unemployment, health care, and education while simultaneously expanding...

 throughout his life.

In 1928, he earned a doctorate in Psychology, under the supervision of Karl Bühler. His dissertation was titled "Die Methodenfrage der Denkpsychologie" (The question of method in cognitive psychology). Then, from 1930 to 1936, he taught secondary school. Popper published his first book, Logik der Forschung (The Logic of Scientific Discovery
The Logic of Scientific Discovery
The Logic of Scientific Discovery is a 1934 book by Karl Popper. It was originally written in German and titled Logik der Forschung. Then Popper reformulated his book in English and republished it in 1959. This forms the rare case of a major work to appear in two languages, both written and one...

), in 1934. Here, he criticised psychologism
Psychologism
Psychologism is a generic type of position in philosophy according to which psychology plays a central role in grounding or explaining some other, non-psychological type of fact or law...

, naturalism
Naturalism (philosophy)
Naturalism commonly refers to the philosophical viewpoint that the natural universe and its natural laws and forces operate in the universe, and that nothing exists beyond the natural universe or, if it does, it does not affect the natural universe that we know...

, inductionism
Inductionism
Inductionism is the scientific philosophy where laws are "induced" from sets of data. As an example, one might measure the strength of electrical forces at varying distances from charges and induce the inverse square law of electrostatics....

, and logical positivism
Logical positivism
Logical positivism is a philosophy that combines empiricism—the idea that observational evidence is indispensable for knowledge—with a version of rationalism incorporating mathematical and logico-linguistic constructs and deductions of epistemology.It may be considered as a type of analytic...

, and put forth his theory of potential falsifiability
Falsifiability
Falsifiability or refutability of an assertion, hypothesis or theory is the logical possibility that it can be contradicted by an observation or the outcome of a physical experiment...

 as the criterion demarcating science from non-science.
In 1937, the rise of Nazism
Nazism
Nazism, the common short form name of National Socialism was the ideology and practice of the Nazi Party and of Nazi Germany...

 and the threat of the Anschluss
Anschluss
The Anschluss , also known as the ', was the occupation and annexation of Austria into Nazi Germany in 1938....

 led Popper to emigrate to New Zealand, where he became lecturer in philosophy at Canterbury University College
University of Canterbury
The University of Canterbury , New Zealand's second-oldest university, operates its main campus in the suburb of Ilam in the city of Christchurch, New Zealand...

 New Zealand
University of New Zealand
The University of New Zealand was the New Zealand university from 1870 to 1961. It was the sole New Zealand university, having a federal structure embracing several constituent colleges at various locations around New Zealand...

 (at Christchurch
Christchurch
Christchurch is the largest city in the South Island of New Zealand, and the country's second-largest urban area after Auckland. It lies one third of the way down the South Island's east coast, just north of Banks Peninsula which itself, since 2006, lies within the formal limits of...

). It was here that he wrote his influential work "The Open Society and its Enemies". In 1946, he moved to England to
become reader
Reader (academic rank)
The title of Reader in the United Kingdom and some universities in the Commonwealth nations like Australia and New Zealand denotes an appointment for a senior academic with a distinguished international reputation in research or scholarship...

 in logic
Logic
In philosophy, Logic is the formal systematic study of the principles of valid inference and correct reasoning. Logic is used in most intellectual activities, but is studied primarily in the disciplines of philosophy, mathematics, semantics, and computer science...

 and scientific method
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...

 at the London School of Economics
London School of Economics
The London School of Economics and Political Science is a public research university specialised in the social sciences located in London, United Kingdom, and a constituent college of the federal University of London...

. Three years later, he was appointed as professor of logic and scientific method at the University of London in 1949. Popper was president of the Aristotelian Society
Aristotelian Society
The Aristotelian Society for the Systematic Study of Philosophy was founded at a meeting on 19 April 1880, at 17 Bloomsbury Square which resolved "to constitute a society of about twenty and to include ladies; the society to meet fortnightly, on Mondays at 8 o'clock, at the rooms of the Spelling...

 from 1958 to 1959. He was knighted
British honours system
The British honours system is a means of rewarding individuals' personal bravery, achievement, or service to the United Kingdom and the British Overseas Territories...

 by Queen Elizabeth II
Elizabeth II of the United Kingdom
Elizabeth II is the constitutional monarch of 16 sovereign states known as the Commonwealth realms: the United Kingdom, Canada, Australia, New Zealand, Jamaica, Barbados, the Bahamas, Grenada, Papua New Guinea, the Solomon Islands, Tuvalu, Saint Lucia, Saint Vincent and the Grenadines, Belize,...

 in 1965, and was elected a Fellow of the Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...

 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
Order of the Companions of Honour
The Order of the Companions of Honour is an order of the Commonwealth realms. It was founded by King George V in June 1917, as a reward for outstanding achievements in the arts, literature, music, science, politics, industry or religion....

 in 1982. Popper was a member of the Academy of Humanism and described himself as an agnostic
Agnosticism
Agnosticism is the view that the truth value of certain claims—especially claims about the existence or non-existence of any deity, but also other religious and metaphysical claims—is unknown or unknowable....

, 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
American Political Science Association
The American Political Science Association is a professional association of political science students and scholars in the United States. Founded in 1903, it publishes three academic journals...

, the Sonning Prize
Sonning Prize
The Sonning Prize is awarded biennially for outstanding contributions to European culture. A committee headed by the rector of the University of Copenhagen decides among candidates proposed by European universities. The prize amounts to 1 mio DKK . The prize award ceremony is held on April 19 at...

, and fellowships in the Royal Society, British Academy
British Academy
The British Academy is the United Kingdom's national body for the humanities and the social sciences. Its purpose is to inspire, recognise and support excellence in the humanities and social sciences, throughout the UK and internationally, and to champion their role and value.It receives an annual...

, London School of Economics, King's College London
King's College London
King's College London is a public research university located in London, United Kingdom and a constituent college of the federal University of London. King's has a claim to being the third oldest university in England, having been founded by King George IV and the Duke of Wellington in 1829, and...

, Darwin College
Darwin College, Cambridge
Darwin College is a constituent college of the University of Cambridge.Founded in 1964, Darwin was Cambridge University's first graduate-only college, and also the first to admit both men and women. The college is named after the family of one of the university's most famous graduates, Charles Darwin...

 Cambridge
University of Cambridge
The University of Cambridge is a public research university located in Cambridge, United Kingdom. It is the second-oldest university in both the United Kingdom and the English-speaking world , and the seventh-oldest globally...

, and Charles University, Prague
Charles University in Prague
Charles University in Prague is the oldest and largest university in the Czech Republic. Founded in 1348, it was the first university in Central Europe and is also considered the earliest German university...

. Austria awarded him the Grand Decoration for Services to the Republic of Austria
Decoration for Services to the Republic of Austria
The Decoration of Honour for Services to the Republic of Austria is a state decoration of the Republic of Austria...

 in Gold.

Popper died in Croydon
Croydon
Croydon is a town in South London, England, located within the London Borough of Croydon to which it gives its name. It is situated south of Charing Cross...

, 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
ORF
ORF may refer to:* ORF , the Austrian public service broadcaster.* Open reading frame, a portion of the genome.* The IATA airport code for Norfolk International Airport in Norfolk, Virginia.* ORF format , Olympus raw image file format....

 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
Critical rationalism
Critical rationalism is an epistemological philosophy advanced by Karl Popper. Popper wrote about critical rationalism in his works, The Open Society and its Enemies Volume 2, and Conjectures and Refutations.- Criticism, not support :...

to describe his philosophy. The term indicates his rejection of classical empiricism
Empiricism
Empiricism is a theory of knowledge that asserts that knowledge comes only or primarily via sensory experience. One of several views of epistemology, the study of human knowledge, along with rationalism, idealism and historicism, empiricism emphasizes the role of experience and evidence,...

, and of the classical observationalist-inductivist
Inductivism
In the philosophy of science inductivism exists both in a classical naive version, which has been highly influential, and in various more sophisticated versions...

 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 historio-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. The term "falsifiable" does not mean something is made false, but rather that, if it is false, it can be shown by observation or experiment. Popper's account of the logical asymmetry between verification
Verification theory
The verification theory is a philosophical theory proposed by the logical positivists of the Vienna Circle. A simplified form of the theory states that a proposition's meaning is determined by the method through which it is empirically verified. In other words, if something cannot be empirically...

 and falsifiability
Falsifiability
Falsifiability or refutability of an assertion, hypothesis or theory is the logical possibility that it can be contradicted by an observation or the outcome of a physical experiment...

 lies at the heart of his philosophy of science. It also inspired him to take falsifiability as his criterion of demarcation
Demarcation problem
The demarcation problem in the philosophy of science is about how and where to draw the lines around science. The boundaries are commonly drawn between science and non-science, between science and pseudoscience, between science and philosophy and between science and religion...

 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
Psychoanalysis
Psychoanalysis is a psychological theory developed in the late 19th and early 20th centuries by Austrian neurologist Sigmund Freud. Psychoanalysis has expanded, been criticized and developed in different directions, mostly by some of Freud's former students, such as Alfred Adler and Carl Gustav...

 and contemporary Marxism
Marxism
Marxism is an economic and sociopolitical worldview and method of socioeconomic inquiry that centers upon a materialist interpretation of history, a dialectical view of social change, and an analysis and critique of the development of capitalism. Marxism was pioneered in the early to mid 19th...

 to scientific status, on the basis that their theories are not falsifiable. Popper also wrote extensively against the famous Copenhagen interpretation
Copenhagen interpretation
The Copenhagen interpretation is one of the earliest and most commonly taught interpretations of quantum mechanics. It holds that quantum mechanics does not yield a description of an objective reality but deals only with probabilities of observing, or measuring, various aspects of energy quanta,...

 of quantum mechanics
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...

. He strongly disagreed with Niels Bohr
Niels Bohr
Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...

's instrumentalism
Instrumentalism
In the philosophy of science, instrumentalism is the view that a scientific theory is a useful instrument in understanding the world. A concept or theory should be evaluated by how effectively it explains and predicts phenomena, as opposed to how accurately it describes objective...

 and supported Albert Einstein
Albert Einstein
Albert Einstein was a German-born theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics and one of the most prolific intellects in human history...

's realist
Scientific realism
Scientific realism is, at the most general level, the view that the world described by science is the real world, as it is, independent of what we might take it to be...

 approach to scientific theories about the universe. Popper's falsifiability resembles Charles Peirce's nineteenth century fallibilism
Fallibilism
Fallibilism is the philosophical principle that human beings could be wrong about their beliefs, expectations, or their understanding of the world...

. 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. Again, in this context the word 'falsified' does not refer to something being 'fake'; rather, that something can be (i.e., is capable of being) shown to be false by observation or experiment. Some things simply do not lend themselves to being shown to be false, and therefore are not falsifiable. 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:


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
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 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 fitness does not ensure 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 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-criticized notion of truth as correspondence
Correspondence theory of truth
The correspondence theory of truth states that the truth or falsity of a statement is determined only by how it relates to the world, and whether it accurately describes that world...

. Then came the semantic theory of truth
Semantic theory of truth
A semantic theory of truth is a theory of truth in the philosophy of language which holds that truth is a property of sentences.-Origin:The semantic conception of truth, which is related in different ways to both the correspondence and deflationary conceptions, is due to work published by Polish...

 formulated by the logician Alfred Tarski
Alfred Tarski
Alfred Tarski was a Polish logician and mathematician. Educated at the University of Warsaw and a member of the Lwow-Warsaw School of Logic and the Warsaw School of Mathematics and philosophy, he emigrated to the USA in 1939, and taught and carried out research in mathematics at the University of...

 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
Truth
Truth has a variety of meanings, such as the state of being in accord with fact or reality. It can also mean having fidelity to an original or to a standard or ideal. In a common usage, it also means constancy or sincerity in action or character...

 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
Metalanguage
Broadly, any metalanguage is language or symbols used when language itself is being discussed or examined. In logic and linguistics, a metalanguage is a language used to make statements about statements in another language...

. 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
Deflationary theory of truth
A deflationary theory of truth is one of a family of theories which all have in common the claim that assertions that predicate truth of a statement do not attribute a property called truth to such a statement.-Redundancy 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:
  1. "John called" is true.
  2. "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
Verisimilitude
Verisimilitude is the quality of realism in something .-Competing ideas:The problem of verisimilitude is the problem of articulating what it takes for one false theory to be closer to the truth than another false theory...

 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
Conjectures and Refutations
Conjectures and Refutations: The Growth of Scientific Knowledge is a book written by philosopher Karl Popper.Published in 1963 by Routledge, this book is a collection of his lectures and papers that summarised his thoughts on the philosophy of science...

. 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 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
Popperian cosmology
Popper's three worlds is a way of looking at reality, described by the Austrian philosopher Karl Popper in a lecture in 1978. The concept involves three interacting worlds, called World 1, World 2 and World 3.-Worlds 1, 2 and 3:...

): 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.

Philosophy of arithmetic


Popper's principle of falsifiability runs into prima facie difficulties when the epistemological status of mathematics is considered. It is difficult to conceive how simple statements of arithmetic, such as 2 + 2 = 4, could ever be shown to be false. If they are not open to falsification they can not be scientific. If they are not scientific, it needs to be explained how they can be informative about real world objects and events.

Popper's solution was an original contribution in the philosophy of mathematics
Philosophy of mathematics
The philosophy of mathematics is the branch of philosophy that studies the philosophical assumptions, foundations, and implications of mathematics. The aim of the philosophy of mathematics is to provide an account of the nature and methodology of mathematics and to understand the place of...

. His idea was that a number statement such as "2 apples + 2 apples = 4 apples" can be taken in two senses. In one sense it is irrefutable and logically true, in the second sense it is factually true and falsifiable. Concisely, the pure mathematics "2 + 2 = 4" is always true, but, when the formula is applied to real world apples, it is open to falsification.

Political philosophy



In The Open Society and Its Enemies
The Open Society and Its Enemies
The Open Society and Its Enemies is an influential two-volume work by Karl Popper written during World War II. Failing to find a publisher in the United States, it was first printed in London by Routledge in 1945...

and The Poverty of Historicism
The Poverty of Historicism
The Poverty of Historicism is a book by twentieth century philosopher Karl Popper which seeks to persuade the reader of both the danger and the bankruptcy of the idea of historicism.-Publication:...

, Popper developed a critique of historicism
Historicism
Historicism is a mode of thinking that assigns a central and basic significance to a specific context, such as historical period, geographical place and local culture. As such it is in contrast to individualist theories of knowledges such as empiricism and rationalism, which neglect the role of...

 and a defence of the 'Open Society'. Popper considered historicism to be the theory that history develops inexorably and necessarily according to knowable general laws towards a determinate end. He argued that this view is the principal theoretical presupposition underpinning most forms of authoritarianism
Authoritarianism
Authoritarianism is a form of social organization characterized by submission to authority. It is usually opposed to individualism and democracy...

 and totalitarianism
Totalitarianism
Totalitarianism is a political system where the state recognizes no limits to its authority and strives to regulate every aspect of public and private life wherever feasible...

. 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. In After The Open Society, which was published posthumously, a large collection of his previously unpublished and uncollected essays on social and political topics was assembled. In this, one can trace his ideas from material that pre-dated The Open Society and Its Enemies to something that was completed just as he died.

In a 1992 lecture, Popper explained the connection between his political philosophy and his philosophy of science. As he stated, he was in his early years impressed by communism and also active in the Austrian Communist party. What had a profound effect on him was an event that happened in 1918: during a riot, caused by the Communists, the police shot several people, including some of Popper's friends. When Popper later told the leaders of the Communist party about this, they responded by stating that this loss of life was necessary in working towards the inevitable workers' revolution. This statement did not convince Popper and he started to think about what kind of reasoning would justify such a statement. He later concluded that there could not be any justification for it, and this was the start of his later criticism of historicism.

In 1947, Popper founded with Friedrich Hayek
Friedrich Hayek
Friedrich August Hayek CH , born in Austria-Hungary as Friedrich August von Hayek, was an economist and philosopher best known for his defense of classical liberalism and free-market capitalism against socialist and collectivist thought...

, Milton Friedman
Milton Friedman
Milton Friedman was an American economist, statistician, academic, and author who taught at the University of Chicago for more than three decades...

, Ludwig von Mises
Ludwig von Mises
Ludwig Heinrich Edler von Mises was an Austrian economist, philosopher, and classical liberal who had a significant influence on the modern Libertarian movement and the "Austrian School" of economic thought.-Biography:-Early life:...

 and others the Mont Pelerin Society
Mont Pelerin Society
The Mont Pelerin Society is an international organization composed of economists , philosophers, historians, intellectuals, business leaders, and others who favour classical liberalism...

 to defend classical liberalism
Classical liberalism
Classical liberalism is the philosophy committed to the ideal of limited government, constitutionalism, rule of law, due process, and liberty of individuals including freedom of religion, speech, press, assembly, and free markets....

, in the spirit of the Open Society.

The paradox of tolerance



Although Popper was an advocate of toleration, he opined that intolerance should not be tolerated.

For, if tolerance allowed intolerance to succeed completely, tolerance itself would be threatened. In The Open Society and Its Enemies: The Spell of Plato
The Open Society and Its Enemies
The Open Society and Its Enemies is an influential two-volume work by Karl Popper written during World War II. Failing to find a publisher in the United States, it was first printed in London by Routledge in 1945...

, he argued that:
Unlimited tolerance must lead to the disappearance of tolerance. If we extend unlimited tolerance even to those who are intolerant, if we are not prepared to defend a tolerant society against the onslaught of the intolerant, then the tolerant will be destroyed, and tolerance with them.
The utterance of intolerant philosophies should not always be suppressed, "as long as we can counter them by rational argument and keep them in check by public opinion." However,
we should claim the right to suppress them if necessary even by force; for it may easily turn out that they are not prepared to meet us on the level of rational argument, but begin by denouncing all argument; they may forbid their followers to listen to rational argument, because it is deceptive, and teach them to answer arguments by the use of their fists or pistols.
Furthermore, in support of human rights
Human rights
Human rights are "commonly understood as inalienable fundamental rights to which a person is inherently entitled simply because she or he is a human being." Human rights are thus conceived as universal and egalitarian . These rights may exist as natural rights or as legal rights, in both national...

 legislation in the second half of the 20th century, he stated:

We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant. We should claim that any movement preaching intolerance places itself outside the law, and we should consider incitement to intolerance and persecution as criminal, in the same way as we should consider incitement to murder, or to kidnapping, or to the revival of the slave trade, as criminal.

Problem of induction


Among his contributions to philosophy is his attempt to answer the philosophical problem of induction
Problem of induction
The problem of induction is the philosophical question of whether inductive reasoning leads to knowledge. That is, what is the justification for either:...

 as emphasized strongly by David Hume
David Hume
David Hume was a Scottish philosopher, historian, economist, and essayist, known especially for his philosophical empiricism and skepticism. He was one of the most important figures in the history of Western philosophy and the Scottish Enlightenment...

. 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 will rise tomorrow? How can one rationally prove that past events will continue to repeat in the future, just because they have repeated in the past?

Popper claims to have found a solution to the problem of induction. His 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 rise, it is possible to formulate the theory that every day the sun will rise—if it does not rise on some particular day, the theory will be falsified and will have to be replaced by a different one. Until that day, there is no need to reject the assumption that the theory is true. Neither is it rational according to Popper to instead make 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.

Such a theory would be true with higher probability, because it cannot be attacked so easily: To falsify the first one, it is sufficient to find that sun has stopped rising; to falsify the second one, one additionally needs the assumption that the given day has not yet been reached. Popper held that it is the least likely, or most easily falsifiable, or simplest theory (attributes which he identified as all the same thing) that explains known facts that one should rationally prefer. His opposition to positivism, which held that it is the theory most likely to be true that one should prefer, here becomes very apparent. It is impossible, Popper argues, to ensure a theory to be true; it is more important that their falsity can be detected as easily as possible.

Popper and Hume agreed that there is often a psychological belief that the sun will rise tomorrow, but both denied that there is logical justification for the supposition that it will, simply because it always has in the past. Popper writes:
"I approached the problem of induction through Hume. Hume, I felt, was perfectly right in pointing out that induction cannot be logically justified." (Conjectures and Refutations, p. 55)


To Popper, who was an anti-justificationist, traditional philosophy is misled by the false principle of sufficient reason
Principle of sufficient reason
The principle of sufficient reason states that anything that happens does so for a reason: no state of affairs can obtain, and no statement can be true unless there is sufficient reason why it should not be otherwise...

. He thinks that no assumption can ever be or needs ever to be justified, so a lack of justification is not a justification for doubt. Instead, theories should be tested and scrutinized. It is not the goal to bless theories with claims of certainty or justification, but to eliminate errors in them:
"there are no such things as good positive reasons; nor do we need such things [...] But [philosophers] obviously cannot quite bring [themselves] to believe that this is my opinion, let alone that it is right" (The Philosophy of Karl Popper, p. 1043)

Free will


Popper and John Eccles speculated on the problem of free will
Free will
"To make my own decisions whether I am successful or not due to uncontrollable forces" -Troy MorrisonA pragmatic definition of free willFree will is the ability of agents to make choices free from certain kinds of constraints. The existence of free will and its exact nature and definition have long...

 for many years generally agreeing on an interactionist dualist theory of mind. However, although 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 first Arthur Holly Compton Memorial Lecture in 1955, Popper revisited the idea of quantum indeterminacy
Quantum indeterminacy
Quantum indeterminacy is the apparent necessary incompleteness in the description of a physical system, that has become one of the characteristics of the standard description of quantum physics...

 as a source of human freedom. Eccles had suggested that "critically poised neurons" might be influenced by the mind to assist in a decision. Popper criticized Compton's idea of amplified quantum events affecting the decision. He wrote

"The idea that the only alternative to determinism is just sheer chance was taken over by Schlick
Moritz Schlick
Friedrich Albert Moritz Schlick was a German philosopher, physicist and the founding father of logical positivism and the Vienna Circle.-Early life and works:...

, together with many of his views on the subject, from Hume
David Hume
David Hume was a Scottish philosopher, historian, economist, and essayist, known especially for his philosophical empiricism and skepticism. He was one of the most important figures in the history of Western philosophy and the Scottish Enlightenment...

, who asserted that 'the removal' of what he called 'physical necessity' must always result in

'the same thing with chance. As objects must either be conjoin'd or not, . . . 'tis impossible to admit of any medium betwixt chance and an absolute necessity'.



"I shall later argue against this important doctrine according to which the alternative to determinism is sheer chance. Yet I must admit that the doctrine seems to hold good for the quantum-theoretical models which have been designed to explain, or at least to illustrate, the possibility of human freedom. This seems to be the reason why these models are so very unsatisfactory.


"Hume's and Schlick's ontological thesis that there cannot exist anything intermediate between chance and determinism seems to me not only highly dogmatic (not to say doctrinaire) but clearly absurd; and it is understandable only on the assumption that they believed in a complete determinism in which chance has no status except as a symptom of our ignorance."


Popper called not for something between chance and necessity but for a combination of randomness and control to explain freedom, though not yet explicitly in two stages with random chance before the controlled decision.

"freedom is not just chance but, rather, the result of a subtle interplay between something almost random or haphazard, and something like a restrictive or selective control."


Then in his 1977 book with John Eccles, The Self and its Brain, Popper finally formulates the two-stage model in a temporal sequence. And he compares free will to Darwinian evolution and natural selection,

"New ideas have a striking similarity to genetic mutations. Now, let us look for a moment at genetic mutations. Mutations are, it seems, brought about by quantum theoretical indeterminacy (including radiation effects). Accordingly, they are also probabilistic and not in themselves originally selected or adequate, but on them there subsequently operates natural selection which eliminates inappropriate mutations. Now we could conceive of a similar process with respect to new ideas and to free-will decisions, and similar things.


"That is to say, a range of possibilities is brought about by a probabilistic and quantum mechanically characterized set of proposals, as it were - of possibilities brought forward by the brain. On these there then operates a kind of selective procedure which eliminates those proposals and those possibilities which are not acceptable to the mind."



Other thinkers who have formulated a two-stage model for free will include William James
William James
William James was a pioneering American psychologist and philosopher who was trained as a physician. He wrote influential books on the young science of psychology, educational psychology, psychology of religious experience and mysticism, and on the philosophy of pragmatism...

, Henri Poincaré
Henri Poincaré
Jules Henri Poincaré was a French mathematician, theoretical physicist, engineer, and a philosopher of science...

, Arthur Compton
Arthur Compton
Arthur Holly Compton was an American physicist and Nobel laureate in physics for his discovery of the Compton effect. He served as Chancellor of Washington University in St. Louis from 1945 to 1953.-Early years:...

, Henry Margenau
Henry Margenau
Henry Margenau was a German-U.S. physicist, and philosopher of science.-Early life:Born Bielefeld, Germany, Margenau obtained his bachelor's degree from Midland Lutheran College, Nebraska before his M.Sc...

, and Daniel Dennett
Daniel Dennett
Daniel Clement Dennett is an American philosopher, writer and cognitive scientist whose research centers on the philosophy of mind, philosophy of science and philosophy of biology, particularly as those fields relate to evolutionary biology and cognitive science. He is currently the Co-director of...

.

Issue of Darwinism



In the creation–evolution controversy, a political debate that is mainly fought between creationists and naturalists (some methodological naturalists, others ontological naturalists), it is an important issue what can legitimately be called science and what cannot be legitimately called science. This is so because US law says that only science may be taught in public school classes. Thus, said controversy raises the issue whether, on the one hand, creationistic ideas, or at least some of them, or at least in some form, may be legitimately called science, and, on the other hand, whether evolution itself may be legitimately called science. For deciding what may legitimately be called science, both sides of the discussion, and even courts in their decisions, have frequently invoked Popper's criterion of falsifiability, and claimed that it presents the distinctive feature of legitimate science.

In this context, passages written by Popper are frequently quoted in which he speaks about such issues himself. For example, he famously stated "Darwinism
Darwinism
Darwinism is a set of movements and concepts related to ideas of transmutation of species or of evolution, including some ideas with no connection to the work of Charles Darwin....

 is not a testable scientific theory, but a metaphysical
Metaphysics
Metaphysics is a branch of philosophy concerned with explaining the fundamental nature of being and the world, although the term is not easily defined. Traditionally, metaphysics attempts to answer two basic questions in the broadest possible terms:...

 research program." He continued:
He also noted that theism
Theism
Theism, in the broadest sense, is the belief that at least one deity exists.In a more specific sense, theism refers to a doctrine concerning the nature of a monotheistic God and God's relationship to the universe....

, presented as explaining adaptation, "was worse than an open admission of failure, for it created the impression that an ultimate explanation had been reached."
He later said

He explained that the difficulty of testing had led some people to describe natural selection as a tautology
Tautology (logic)
In logic, a tautology is a formula which is true in every possible interpretation. Philosopher Ludwig Wittgenstein first applied the term to redundancies of propositional logic in 1921; it had been used earlier to refer to rhetorical tautologies, and continues to be used in that alternate sense...

, 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 (as is a tautology) and yet of great scientific interest.
Popper summarized his new view as follows:

These frequently quoted passages are only a very small part of what Popper wrote on the issue of evolution, however, and give the wrong impression that he mainly discussed questions of its falsifiability. Popper never invented this criterion to give justifiable use of words like science. In fact, Popper says at the very beginning of his Logic of Scientific Discovery that it is not his plan to define science, and that science can, in fact, be defined quite arbitrarily.

Popper had his very own sophisticated views on evolution that go much beyond what the frequently quoted passages say. In effect, Popper agreed with some of the points of both creationists and naturalists, but, on the other hand, also disagreed with both views on crucial aspects. 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. Still, he accepted the creationistic criticism that an explanation is needed for all the purpose in the world, and that this can hardly be explained by purely naturalistic evolution. He said that evolution must be, as the creationists say, work in a goal-directed way, but he disagreed with their view that it must necessarily be the hand of god that imposes these goals onto the stage of live. Instead, he invented the such-called spearhead theory of evolution, a version of genetic pluralism. This theory says that the living organisms themselves have goals, and act according to these goals, each guided by a central control (in its most sophisticated form, this is the brain of humans, but controls also exist in much less sophisticated ways for species of lower complexity, such as the amoeba
Amoeba
Amoeba is a genus of Protozoa.History=The amoeba was first discovered by August Johann Rösel von Rosenhof in 1757. Early naturalists referred to Amoeba as the Proteus animalcule after the Greek god Proteus, who could change his shape...

). These goals bring the purpose into the world. Mutations in the genes that determine the structure of the control may then cause drastic changes in behaviour, preferences and goals, without having an impact on the organism's phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...

. Popper postulates that such purely behavioral changes are less likely to be lethal for the organism compared to drastic changes of the phenotype. Popper contrasts his views with the notion of the "hopeful monster" that has large phenotype mutations and calls it the "hopeful behavioral monster". After behavior has changed radically, small but quick changes of the phenotype follow to make the organism fitter to its changed goals. This way it looks as if the phenotype were changing guided by some invisible hand, while it is merely natural selection working in combination with the new behaviour. For example, according to this hypothesis, the eating habits of the giraffe must have changed before its elongated neck evolved. Popper contrasted this view as evolution from within (the organism actively trying to discover new ways of life and being on a quest for conquering new ecological niches), with the naturalistic evolution from without (which has the picture of a hostile environment only trying to kill the mostly passive organism, or perhaps segregate some of its groups).

Influence



Popper played a vital role in establishing the philosophy of science
Philosophy of science
The philosophy of science is concerned with the assumptions, foundations, methods and implications of science. It is also concerned with the use and merit of science and sometimes overlaps metaphysics and epistemology by exploring whether scientific results are actually a study of truth...

 as a vigorous, autonomous discipline within analytic philosophy
Analytic philosophy
Analytic philosophy is a generic term for a style of philosophy that came to dominate English-speaking countries in the 20th century...

, 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
London School of Economics
The London School of Economics and Political Science is a public research university specialised in the social sciences located in London, United Kingdom, and a constituent college of the federal University of London...

 and there lectured and influenced both Imre Lakatos
Imre Lakatos
Imre Lakatos was a Hungarian philosopher of mathematics and science, known for his thesis of the fallibility of mathematics and its 'methodology of proofs and refutations' in its pre-axiomatic stages of development, and also for introducing the concept of the 'research programme' in his...

 and Paul Feyerabend
Paul Feyerabend
Paul Karl Feyerabend was an Austrian-born philosopher of science best known for his work as a professor of philosophy at the University of California, Berkeley, where he worked for three decades . He lived a peripatetic life, living at various times in England, the United States, New Zealand,...

, 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 is some dispute as to the matter of influence, Popper had a long-standing and close friendship with economist Friedrich Hayek
Friedrich Hayek
Friedrich August Hayek CH , born in Austria-Hungary as Friedrich August von Hayek, was an economist and philosopher best known for his defense of classical liberalism and free-market capitalism against socialist and collectivist thought...

, 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 have learnt more from you than from any other living thinker, except perhaps Alfred Tarski
Alfred Tarski
Alfred Tarski was a Polish logician and mathematician. Educated at the University of Warsaw and a member of the Lwow-Warsaw School of Logic and the Warsaw School of Mathematics and philosophy, he emigrated to the USA in 1939, and taught and carried out research in mathematics at the University of...

." Popper dedicated his Conjectures and Refutations
Conjectures and Refutations
Conjectures and Refutations: The Growth of Scientific Knowledge is a book written by philosopher Karl Popper.Published in 1963 by Routledge, this book is a collection of his lectures and papers that summarised his thoughts on the philosophy of science...

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 have been a complete adherent to his general theory of methodology."

Popper also had long and mutually influential friendships with art historian Ernst Gombrich
Ernst Gombrich
Sir Ernst Hans Josef Gombrich, OM, CBE was an Austrian-born art historian who became naturalized British citizen in 1947. He spent most of his working life in the United Kingdom...

, biologist Peter Medawar
Peter Medawar
Sir Peter Brian Medawar OM CBE FRS was a British biologist, whose work on graft rejection and the discovery of acquired immune tolerance was fundamental to the practice of tissue and organ transplants...

, and neuro-scientist John Carew Eccles
John Carew Eccles
John Carew Eccles, AC FRS FRACP FRSNZ FAAS was an Australian neurophysiologist who won the 1963 Nobel Prize in Physiology or Medicine for his work on the synapse. He shared the prize with Andrew Huxley and Alan Lloyd Hodgkin....

.

Popper's influence, both through his work in philosophy of science and through his political philosophy, has also extended beyond the academy. One of Popper's students at the London School of Economics was the billionaire investor George Soros
George Soros
George Soros is a Hungarian-American business magnate, investor, philosopher, and philanthropist. He is the chairman of Soros Fund Management. Soros supports progressive-liberal causes...

, among whose philanthropic
Philanthropy
Philanthropy etymologically means "the love of humanity"—love in the sense of caring for, nourishing, developing, or enhancing; humanity in the sense of "what it is to be human," or "human potential." In modern practical terms, it is "private initiatives for public good, focusing on quality of...

 foundations is the Open Society Institute
Open Society Institute
The Open Society Institute , renamed in 2011 to Open Society Foundations, is a private operating and grantmaking foundation started by George Soros, aimed to shape public policy to promote democratic governance, human rights, and economic, legal, and social reform...

, a think-tank named in honor of Popper's The Open Society and Its Enemies
The Open Society and Its Enemies
The Open Society and Its Enemies is an influential two-volume work by Karl Popper written during World War II. Failing to find a publisher in the United States, it was first printed in London by Routledge in 1945...

.

Popperian philosophy also inspired the creation of Taking Children Seriously
Taking Children Seriously
Taking Children Seriously is a parenting movement and educational philosophy whose central idea is that it is possible and desirable to raise and educate children without either doing anything to them against their will, or making them do anything against their will.It was founded in 1994 as an...

, a libertarian movement which noticed that Popper's general theory of knowledge creation does not differentiate between adults and children.

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 is 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 have survived this particularly vigorous selection method. He does not argue that any such conclusions are therefore true, or that this describes the actual methods of any particular scientist.

Rather, it is 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
Logical positivism
Logical positivism is a philosophy that combines empiricism—the idea that observational evidence is indispensable for knowledge—with a version of rationalism incorporating mathematical and logico-linguistic constructs and deductions of epistemology.It may be considered as a type of analytic...

, the followers of which mistook his aims for their own.

The Quine-Duhem thesis
Confirmation holism
Confirmation holism, also called epistemological holism is the claim that a single scientific theory cannot be tested in isolation; a test of one theory always depends on other theories and hypotheses....

 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 cannot conclusively say which element of the package must be replaced. An example of this is given by the discovery of the planet Neptune
Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...

: when the motion of Uranus
Uranus
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...

 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
The Logic of Scientific Discovery
The Logic of Scientific Discovery is a 1934 book by Karl Popper. It was originally written in German and titled Logik der Forschung. Then Popper reformulated his book in English and republished it in 1959. This forms the rare case of a major work to appear in two languages, both written and one...

. For Popper, theories are accepted or rejected via a sort of selection process. 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
Thomas Kuhn
Thomas Samuel Kuhn was an American historian and philosopher of science whose controversial 1962 book The Structure of Scientific Revolutions was deeply influential in both academic and popular circles, introducing the term "paradigm shift," which has since become an English-language staple.Kuhn...

’s influential book The Structure of Scientific Revolutions
The Structure of Scientific Revolutions
The Structure of Scientific Revolutions , by Thomas Kuhn, is an analysis of the history of science. Its publication was a landmark event in the history, philosophy, and sociology of scientific knowledge and it triggered an ongoing worldwide assessment and reaction in — and beyond — those scholarly...

argued that scientists work in a series of paradigm
Paradigm
The word paradigm has been used in science to describe distinct concepts. It comes from Greek "παράδειγμα" , "pattern, example, sample" from the verb "παραδείκνυμι" , "exhibit, represent, expose" and that from "παρά" , "beside, beyond" + "δείκνυμι" , "to show, to point out".The original Greek...

s, and that falsificationist methodologies would make science impossible. Popper's student Imre Lakatos
Imre Lakatos
Imre Lakatos was a Hungarian philosopher of mathematics and science, known for his thesis of the fallibility of mathematics and its 'methodology of proofs and refutations' in its pre-axiomatic stages of development, and also for introducing the concept of the 'research programme' in his...

 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
Universal quantification
In predicate logic, universal quantification formalizes the notion that something is true for everything, or every relevant thing....

 of naïve falsificationism. Another of Popper’s students Paul Feyerabend
Paul Feyerabend
Paul Karl Feyerabend was an Austrian-born philosopher of science best known for his work as a professor of philosophy at the University of California, Berkeley, where he worked for three decades . He lived a peripatetic life, living at various times in England, the United States, New Zealand,...

 ultimately rejected any prescriptive methodology, and argued that the only universal method characterizing scientific progress was anything goes.

Popper claimed to have recognized 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'. (But Popper criticised what he saw as Kuhn's relativism.) Also, in his collection Conjectures and Refutations
Conjectures and Refutations
Conjectures and Refutations: The Growth of Scientific Knowledge is a book written by philosopher Karl Popper.Published in 1963 by Routledge, this book is a collection of his lectures and papers that summarised his thoughts on the philosophy of science...

: 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 is not always possible to demonstrate falsehood definitively, especially if one is using statistical
Statistical significance
In statistics, a result is called statistically significant if it is unlikely to have occurred by chance. The phrase test of significance was coined by Ronald Fisher....

 criteria to evaluate a null hypothesis
Null hypothesis
The practice of science involves formulating and testing hypotheses, assertions that are capable of being proven false using a test of observed data. The null hypothesis typically corresponds to a general or default position...

. More generally it is not always clear, 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 offering 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: it is not clear how Popper would deal with a statement like "for every metal, there is a temperature at which it will melt." The hypothesis cannot be falsified by any possible observation, for there will always be a higher temperature than tested at which the metal may in fact melt, yet it seems to be a valid scientific hypothesis. These examples were pointed out by Carl Gustav Hempel
Carl Gustav Hempel
Carl Gustav "Peter" Hempel was a philosopher of science and a major figure in 20th-century logical empiricism...

. 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
Atomic theory
In chemistry and physics, atomic theory is a theory of the nature of matter, which states that matter is composed of discrete units called atoms, as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity...

 implies that all metals melt at some temperature.

An early adversary of so-called critical rationalism, Karl-Otto Apel
Karl-Otto Apel
Karl-Otto Apel is a German philosopher and Professor Emeritus at the University of Frankfurt am Main. Apel worked in ethics, the philosophy of language and human sciences. He wrote extensively in these fields, publishing mostly in German...

 attempted a comprehensive refutation of Popper's philosophy. In Transformation der Philosophie (1973), Apel charged Popper with being guilty of, amongst other things, a pragmatic contradiction.

Other criticism


It has been argued that Popper's student Imre Lakatos
Imre Lakatos
Imre Lakatos was a Hungarian philosopher of mathematics and science, known for his thesis of the fallibility of mathematics and its 'methodology of proofs and refutations' in its pre-axiomatic stages of development, and also for introducing the concept of the 'research programme' in his...

 transformed Popper's philosophy using historicism and updated Hegelian historiographic ideas.

Ludwig Wittgenstein
Ludwig Wittgenstein
Ludwig Josef Johann Wittgenstein was an Austrian philosopher who worked primarily in logic, the philosophy of mathematics, the philosophy of mind, and the philosophy of language. He was professor in philosophy at the University of Cambridge from 1939 until 1947...

 was accused of brandishing a poker at Popper during a meeting of the Cambridge Moral Sciences Club
Cambridge University Moral Sciences Club
The Cambridge University Moral Sciences Club, founded in October 1878, is a philosophy discussion group that meets weekly at Cambridge during term time. Speakers are invited to give a 30-minute paper, after which discussion is thrown open for several hours....

, when they argued about whether issues in philosophy were real or just linguistic puzzles. Wittgenstein's friends say he was merely handling a poker, but Popper used the situation to make a joke at Wittgenstein's expense.

Charles Taylor
Charles Taylor (philosopher)
Charles Margrave Taylor, is a Canadian philosopher from Montreal, Quebec best known for his contributions in political philosophy, the philosophy of social science, and in the history of philosophy. His contributions to these fields have earned him both the prestigious Kyoto Prize and the...

 accuses Popper of exploiting his worldwide fame as an epistemologist to diminish the importance of philosophers of the 20th century continental tradition
Continental philosophy
Continental philosophy, in contemporary usage, refers to a set of traditions of 19th and 20th century philosophy from mainland Europe. This sense of the term originated among English-speaking philosophers in the second half of the 20th century, who used it to refer to a range of thinkers and...

. According to Taylor, Popper's criticisms are completely baseless, but they are received with an attention and respect that Popper's "intrinsic worth hardly merits". William W. Bartley defended Popper against such allegations: "Sir Karl Popper is not really a participant in the contemporary professional philosophical dialogue; quite the contrary, he has ruined that dialogue. If he is 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
Psychologist
Psychologist is a professional or academic title used by individuals who are either:* Clinical professionals who work with patients in a variety of therapeutic contexts .* Scientists conducting psychological research or teaching psychology in a college...

 Michel ter Hark (Groningen, The Netherlands) published a book, called Popper, Otto Selz and the rise of evolutionary epistemology, ISBN 0-521-83074-5, in which he claimed that Popper took some of his ideas from his tutor, the German psychologist Otto Selz
Otto Selz
Otto Selz was a German psychologist from Munich, Bavaria, who formulated the first nonassociationist theory of thinking, in 1913. Selz used the method of introspection, but unlike his predecessors, his theory developed without the use of images and associations...

. Selz himself never published his ideas, partly because of the rise of Nazism
Nazism
Nazism, the common short form name of National Socialism was the ideology and practice of the Nazi Party and of Nazi Germany...

 which forced him to quit his work in 1933, and the prohibition of referring to Selz' work. Popper, the historian of ideas and his scholarship, is criticized in some academic quarters, for his rejection of Plato, Hegel and Marx.

According to John N. Gray, Popper held that "a theory is scientific only in so far as it is falsifiable, and should be given up as soon as it is falsified." By applying Popper's account of scientific method, Gray's Straw Dogs states that this would have "killed the theories of Darwin and Einstein at birth." When they were first advanced, Gray claims, each of them was "at odds with some available evidence; only later did evidence become available that gave them crucial support." Against this, Gray seeks to establish the irrationalist thesis that "the progress of science comes from acting against reason."

Gray does not, however, give any indication of what available evidence these theories were at odds with, and his appeal to "crucial support" illustrates the very inductivist approach to science that Popper sought to show was logically illegitimate. For, according to Popper, Einstein's theory was at least equally as well corroborated as Newton's upon its initial conception; they both equally well accounted for all the hitherto available evidence. Moreover, since Einstein also explained the empirical refutations of Newton's theory, general relativity was immediately deemed suitable for tentative acceptance on the Popperian account. Indeed, Popper wrote, several decades before Gray's criticism, in reply to a critical essay by Imre Lakatos
Imre Lakatos
Imre Lakatos was a Hungarian philosopher of mathematics and science, known for his thesis of the fallibility of mathematics and its 'methodology of proofs and refutations' in its pre-axiomatic stages of development, and also for introducing the concept of the 'research programme' in his...

:

"It is true that I have used the terms "elimination", and even "rejection" when discussing "refutation". But it is clear from my main discussion that these terms mean, when applied to a scientific theory, that it is eliminated as a contender for the truth- that is, refuted, but not necessarily abandoned. Moreover, I have often pointed out that any such refutation is fallible. It is a typical matter of conjecture and of risk-taking whether or not we accept a refutation and, furthermore, of whether we "abandon" a theory or, say, only modify it, or even stick to it, and try to find some alternative, and methodologically acceptable, way round the problem involved. That I do not conflate even admitted falsity with the need to abandon a theory may be seen from the fact that I have frequently pointed out, that Einstein regarded general relativity as false, yet as a better approximation to the truth than Newton's gravitational theory. He certainly did not "abandon" it. But he worked to the end of his life in an attempt to improve upon it by way of a further generalization."


See also

  • Calculus of predispositions
    Calculus of predispositions
    Calculus of predispositions is a basic part of predispositioning theory and belongs to the indeterministic procedures.-Introduction:“The key component of any indeterministic procedure is the evaluation of a position...

  • Contributions to liberal theory
    Contributions to liberal theory
    Individual contributors to classical liberalism and political liberalism are associated with philosophers of the Enlightenment. Liberalism as a specifically named ideology begins in the late 18th century as a movement towards self-government and away from aristocracy...

  • Evolutionary epistemology
    Evolutionary epistemology
    Evolutionary epistemology refers to two distinct topics - on the one hand, the biological evolution of cognitive mechanisms in animals and humans, and on the other hand, a theory in that knowledge itself evolves by natural selection....

  • Liberalism
    Liberalism
    Liberalism is the belief in the importance of liberty and equal rights. Liberals espouse a wide array of views depending on their understanding of these principles, but generally, liberals support ideas such as constitutionalism, liberal democracy, free and fair elections, human rights,...

  • Liberalism in Austria
    Liberalism in Austria
    This article gives an overview of liberalism in Austria. It is limited to liberal parties with substantial support, mainly proved by having had a representation in parliament. The sign ⇒ denotes another party in that scheme...

  • Popper's experiment
    Popper's experiment
    Popper's experiment is an experiment proposed by the 20th century philosopher of science Karl Popper, an advocate of an objective interpretation of quantum mechanics. He wanted to test the Copenhagen interpretation, a popular subjectivist interpretation of quantum mechanics...

     (quantum mechanics)
  • Popperian cosmology
    Popperian cosmology
    Popper's three worlds is a way of looking at reality, described by the Austrian philosopher Karl Popper in a lecture in 1978. The concept involves three interacting worlds, called World 1, World 2 and World 3.-Worlds 1, 2 and 3:...

  • Predispositioning Theory
    Predispositioning Theory
    Predispositioning theory in the field of decision theory and systems theory is a theory, that focused on the intermediate stage between a complete order and a complete disorder....


Further reading


  • [Comprehensive bibliography:] Lube, Manfred: Karl R. Popper. Bibliographie 1925–2004. Wissenschaftstheorie, Sozialphilosophie, Logik, Wahrscheinlichkeitstheorie, Naturwissenschaften. Frankfurt/Main etc.: Peter Lang, 2005. 576 pp. (Schriftenreihe der Karl Popper Foundation Klagenfurt.3.)- Current edition
  • Stefano Gattei. Karl Popper's Philosophy of Science. 2009.
  • David Miller
    David Miller (philosopher)
    David W. Miller is a philosopher and prominent exponent of critical rationalism. He taught in the Department of Philosophy at the University of Warwick in Coventry, UK....

    . Critical Rationalism: A Restatement and Defence. 1994.
  • David Miller (Ed.). Popper Selections.
  • John W. N. Watkins
    John W. N. Watkins
    John William Nevill Watkins was an English philosopher, a professor at the London School of Economics from 1966 until his retirement in 1989 and a prominent proponent of Critical rationalism....

    . Science and Skepticism. 1984.
  • Bailey, Richard, Education in the Open Society: Karl Popper and Schooling. Aldershot, UK: Ashgate 2000. The only book-length examination of Popper's relevance to education.
  • Bartley, William Warren III. Unfathomed Knowledge, Unmeasured Wealth. La Salle, IL: Open Court Press 1990. A look at Popper and his influence by one of his students.
  • Berkson, William K., and Wettersten, John. Learning from Error: Karl Popper's Psychology of Learning. La Salle, IL: Open Court 1984
  • Edmonds, D., Eidinow, J. Wittgenstein's Poker. New York: Ecco 2001. A review of the origin of the conflict between Popper and Ludwig Wittgenstein
    Ludwig Wittgenstein
    Ludwig Josef Johann Wittgenstein was an Austrian philosopher who worked primarily in logic, the philosophy of mathematics, the philosophy of mind, and the philosophy of language. He was professor in philosophy at the University of Cambridge from 1939 until 1947...

    , focused on events leading up to their volatile first encounter at 1946 Cambridge meeting.
  • Feyerabend, Paul Against Method. London: New Left Books, 1975. A polemical, iconoclastic book by a former colleague of Popper's. Vigorously critical of Popper's rationalist view of science.
  • Hacohen, M. Karl Popper: The Formative Years, 1902–1945. Cambridge: Cambridge University Press, 2000.
  • Hickey, J. Thomas. History of the Twentieth-Century Philosophy of Science Book V, Karl Popper And Falsificationist Criticism. www.philsci.com . 1995* Kadvany, John Imre Lakatos and the Guises of Reason. Durham and London: Duke University Press, 2001. ISBN 0-8223-2659-0. Explains how Imre Lakatos developed Popper's philosophy into a historicist and critical theory of scientific method.
  • Keuth, Herbert. The Philosophy of Karl Popper. Cambridge: Cambridge University Press, 2004. An accurate scholarly overview of Popper's philosophy, ideal for students.
  • Kuhn, Thomas S. The Structure of Scientific Revolutions. Chicago: University of Chicago Press, 1962. Central to contemporary philosophy of science is the debate between the followers of Kuhn and Popper on the nature of scientific enquiry. This is the book in which Kuhn's views received their classical statement.
  • Lakatos, I & Musgrave, A (eds.) (1970), Criticism and the Growth of Knowledge, Cambridge (Cambridge University Press). ISBN 0-521-07826-1
  • Levinson, Paul
    Paul Levinson
    Paul Levinson is an American author and professor of communications and media studies at Fordham University in New York City. Levinson's novels, short fiction, and non-fiction works have been translated into twelve languages....

    , ed. In Pursuit of Truth: Essays on the Philosophy of Karl Popper on the Occasion of his 80th Birthday. Atlantic Highlands, NJ: Humanities Press, 1982. A collection of essays on Popper's thought and legacy by a wide range of his followers. Includes an interview with Sir Ernst Gombrich
    Ernst Gombrich
    Sir Ernst Hans Josef Gombrich, OM, CBE was an Austrian-born art historian who became naturalized British citizen in 1947. He spent most of his working life in the United Kingdom...

    .
  • Magee, Bryan. Popper. London: Fontana, 1977. An elegant introductory text. Very readable, albeit rather uncritical of its subject, by a former Member of Parliament.
  • Magee, Bryan. Confessions of a Philosopher, Weidenfeld and Nicolson, 1997. Magee's philosophical autobiography, with a chapter on his relations with Popper. More critical of Popper than in the previous reference.
  • Munz, Peter. Beyond Wittgenstein's Poker: New Light on Popper and Wittgenstein Aldershot, Hampshire, UK: Ashgate, 2004. ISBN 0-7546-4016-7. Written by the only living student of both Wittgenstein and Popper, an eyewitness to the famous "poker" incident described above (Edmunds & Eidinow). Attempts to synthesize and reconcile the differences between these two philosophers.
  • Niemann, Hans-Joachim
    Hans-Joachim Niemann
    Hans Joachim Niemann, born in 1941 in Kiel , is a German philosopher who has developed the methods of critical rationalism for applying them in the fields of metaphysics and ethics.-Biography:...

    . Lexikon des Kritischen Rationalismus, (Encyclopaedia of Critical Raionalism), Tübingen (Mohr Siebeck) 2004, ISBN 3-16-148395-2. More than a thousand headwords about critical rationalism, the most important arguments of K.R. Popper and H. Albert, quotations of the original wording. Edition for students in 2006, ISBN 3-16-149158-0.
  • Notturno, Mark Amadeus. "Objectivity, Rationality, and the Third Realm: Justification and the Grounds of Psychologism". Boston: Martinus Nijhoff, 1985.
  • Notturno, Mark Amadeus. On Popper. Wadsworth Philosophers Series. 2003. A very comprehensive book on Popper’s philosophy by an accomplished Popperian.
  • Notturno, Mark Amadeus. "Science and the Open Society". New York: CEU Press, 2000.
  • O'Hear, Anthony. Karl Popper. London: Routledge, 1980. A critical account of Popper's thought, viewed from the perspective of contemporary analytic philosophy.
  • Radnitzky, Gerard, Bartley, W. W., III eds. Evolutionary Epistemology, Rationality, and the Sociology of Knowledge. La Salle, IL: Open Court Press 1987. ISBN 0-8126-9039-7. A strong collection of essays by Popper, Campbell, Munz, Flew, et al., on Popper's epistemology and critical rationalism. Includes a particularly vigorous answer to Rorty's criticisms.
  • Richmond, Sheldon. Aesthetic Criteria: Gombrich and the Philosophies of Science of Popper and Polanyi. Rodopi, Amsterdam/Atlanta, 1994, 152 pp. ISBN 90-5183-618-X.
  • Rowbottom, Darrell P. Popper's Critical Rationalism: A Philosophical Investigation. London: Routledge, 2010. A research monograph on Popper's philosophy of science and epistemology. It critiques and develops critical rationalism in light of more recent advances in mainstream philosophy.
  • Schilpp, Paul A.
    Paul Arthur Schilpp
    Paul Arthur Schilpp was an American educator.He was born in Germany and immigrated to the United States prior to World War I...

    , ed. The Philosophy of Karl Popper, 2 vols. La Salle, IL: Open Court Press, 1974. One of the better contributions to the Library of Living Philosophers
    Library of Living Philosophers
    The Library of Living Philosophers is a series of books conceived of and started by Paul Arthur Schilpp in 1939; Schilpp remained editor until 1981. The series was edited by Lewis Edwin Hahn from 1981 until 2001, and is currently edited by Randall Auxier...

     series. Contains Popper's intellectual autobiography, a comprehensive range of critical essays, and Popper's responses to them. ISBN 0-87548-141-8 (vol.I). ISBN 0-87548-142-6 (Vol II)
  • Schroeder-Heister, P. "Popper, Karl Raimund (1902–94)," International Encyclopedia of the Social & Behavioral Sciences
    International Encyclopedia of the Social & Behavioral Sciences
    The International Encyclopedia of the Social & Behavioral Sciences , edited by Neil J. Smelser andPaul B. Baltes, is a 26-volume work. It has some 4,000 signed articles, commissioned by around 50 subject editors, and includes biographical entries, 122,400 entries, and an extensivehierarchical...

    , 2001, pp. 11727–11733.Abstract.
  • Shearmur, Jeremy. The Political Thought of Karl Popper. London and New York: Routledge, 1996. Study of Popper's political thought by a former assistant of Popper's. Makes use of archive sources and studies the development of Popper's political thought and its inter-connections with his epistemology.
  • Stokes, G. Popper: Philosophy, Politics and Scientific Method. Cambridge: Polity Press, 1998. A very comprehensive, balanced study, which focuses largely on the social and political side of Popper's thought.
  • Stove, D.C.
    David Stove
    David Charles Stove , was an Australian philosopher of science.His work in philosophy of science included detailed criticisms of David Hume's inductive skepticism, as well as what he regarded as the irrationalism of his disciplinary contemporaries Karl Popper, Thomas Kuhn, Imre Lakatos, and Paul...

    , Popper and After
    Popper and After
    Popper and After is a book by David Charles Stove first published by Pergamon Press in 1982. It was subtitled Four Modern Irrationalists...

    : Four Modern Irrationalists
    . Oxford: Pergamon. 1982. A vigorous attack, especially on Popper's restricting himself to deductive logic.
  • Thornton, Stephen. "Karl Popper," Stanford Encyclopedia of Philosophy
    Stanford Encyclopedia of Philosophy
    The Stanford Encyclopedia of Philosophy is a freely-accessible online encyclopedia of philosophy maintained by Stanford University. Each entry is written and maintained by an expert in the field, including professors from over 65 academic institutions worldwide...

    ,
    2006.
  • Weimer, W., Palermo, D., eds. Cognition and the Symbolic Processes. Hillsdale, NJ: Lawrence Erlbaum Associates. 1982. See Hayek's essay, "The Sensory Order after 25 Years", and "Discussion".


External links



, 8 February 2007. Discussion with John Worrall, Professor of Philosophy of Science at the London School of Economics
London School of Economics
The London School of Economics and Political Science is a public research university specialised in the social sciences located in London, United Kingdom, and a constituent college of the federal University of London...

, Anthony O'Hear, Weston Professor of Philosophy at Buckingham University
University of Buckingham
The University of Buckingham is an independent, non-sectarian, research and teaching university located in Buckingham, Buckinghamshire, England, on the banks of the River Great Ouse. It was originally founded as Buckingham University College in the 1970s and received its Royal Charter from the...

, Nancy Cartwright, Professor of Philosophy at the LSE and the University of California
University of California
The University of California is a public university system in the U.S. state of California. Under the California Master Plan for Higher Education, the University of California is a part of the state's three-tier public higher education system, which also includes the California State University...

, hosted by Melvyn Bragg
Melvyn Bragg
Melvyn Bragg, Baron Bragg FRSL FRTS FBA, FRS FRSA is an English broadcaster and author best known for his work with the BBC and for presenting the The South Bank Show...

.