K. R. Popper
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Sir Karl Raimund Popper (28 July 1902 – 17 September 1994) was an Austrian-British
philosopher A philosopher is a person who practices or investigates philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , translit=philosophos, meaning 'lover of wisdom'. The coining of the term has been attributed to the Greek th ...
,
academic An academy (Attic Greek: Ἀκαδήμεια; Koine Greek Ἀκαδημία) is an institution of secondary or tertiary higher learning (and generally also research or honorary membership). The name traces back to Plato's school of philosophy, ...
and social commentator. One of the 20th century's most influential
philosophers of science Philosophy of science is a branch of philosophy concerned with the foundations, methods, and implications of science. The central questions of this study concern what qualifies as science, the reliability of scientific theories, and the ultim ...
, Popper is known for his rejection of the classical inductivist views on the
scientific method The scientific method is an empirical method for acquiring knowledge that has characterized the development of science since at least the 17th century (with notable practitioners in previous centuries; see the article history of scientifi ...
in favour of empirical falsification. According to Popper, a theory in the empirical sciences can never be proven, but it can be falsified, meaning that it can (and should) be scrutinised with decisive experiments. Popper was opposed to the classical
justificationist Critical rationalism is an epistemological philosophy advanced by Karl Popper on the basis that, if a statement cannot be logically deduced (from what is known), it might nevertheless be possible to logically falsify it. Following David Hume, Hum ...
account of knowledge, which he replaced with
critical rationalism Critical rationalism is an epistemological philosophy advanced by Karl Popper on the basis that, if a statement cannot be logically deduced (from what is known), it might nevertheless be possible to logically falsify it. Following Hume, Popper ...
, namely "the first non-justificational philosophy of criticism in the history of philosophy". In political discourse, he is known for his vigorous defence of
liberal democracy Liberal democracy is the combination of a liberal political ideology that operates under an indirect democratic form of government. It is characterized by elections between multiple distinct political parties, a separation of powers into ...
and the principles of
social criticism Social criticism is a form of academic or journalistic criticism focusing on social issues in contemporary society, in particular with respect to perceived injustices and power relations in general. Social criticism of the Enlightenment The or ...
that he believed made a flourishing
open society Open society (french: société ouverte) is a term coined by French philosopher Henri Bergson in 1932, and describes a dynamic system inclined to moral universalism.Thomas Mautner (2005), 2nd ed. ''The Penguin Dictionary of Philosophy'' Open s ...
possible. His
political philosophy Political philosophy or political theory is the philosophical study of government, addressing questions about the nature, scope, and legitimacy of public agents and institutions and the relationships between them. Its topics include politics, ...
embraced ideas from major democratic political ideologies, including
socialism Socialism is a left-wing economic philosophy and movement encompassing a range of economic systems characterized by the dominance of social ownership of the means of production as opposed to private ownership. As a term, it describes th ...
/
social democracy Social democracy is a political, social, and economic philosophy within socialism that supports political and economic democracy. As a policy regime, it is described by academics as advocating economic and social interventions to promote s ...
,
libertarianism Libertarianism (from french: libertaire, "libertarian"; from la, libertas, "freedom") is a political philosophy that upholds liberty as a core value. Libertarians seek to maximize autonomy and political freedom, and minimize the state's en ...
/
classical liberalism Classical liberalism is a political tradition and a branch of liberalism that advocates free market and laissez-faire economics; civil liberties under the rule of law with especial emphasis on individual autonomy, limited government, e ...
and
conservatism Conservatism is a cultural, social, and political philosophy that seeks to promote and to preserve traditional institutions, practices, and values. The central tenets of conservatism may vary in relation to the culture and civilizati ...
, and attempted to reconcile them.


Life and career


Family and training

Karl Popper was born in
Vienna en, Viennese , iso_code = AT-9 , registration_plate = W , postal_code_type = Postal code , postal_code = , timezone = CET , utc_offset = +1 , timezone_DST ...
(then in
Austria-Hungary Austria-Hungary, often referred to as the Austro-Hungarian Empire,, the Dual Monarchy, or Austria, was a constitutional monarchy and great power in Central Europe between 1867 and 1918. It was formed with the Austro-Hungarian Compromise of ...
) in 1902 to
upper-middle-class In sociology, the upper middle class is the social group constituted by higher status members of the middle class. This is in contrast to the term ''lower middle class'', which is used for the group at the opposite end of the middle-class strat ...
parents. All of Popper's grandparents were
Jewish Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
, but they were not devout and as part of the
cultural assimilation Cultural assimilation is the process in which a minority group or culture comes to resemble a society's majority group or assume the values, behaviors, and beliefs of another group whether fully or partially. The different types of cultural ass ...
process the Popper family converted to
Lutheranism Lutheranism is one of the largest branches of Protestantism, identifying primarily with the theology of Martin Luther, the 16th-century German monk and Protestant Reformers, reformer whose efforts to reform the theology and practice of the Cathol ...
before he was born Magee, Bryan. ''The Story of Philosophy.'' New York: DK Publishing, 2001. p. 221, and so he received a Lutheran baptism. His father, Simon Siegmund Carl Popper (1856-1932), was a lawyer from
Bohemia Bohemia ( ; cs, Čechy ; ; hsb, Čěska; szl, Czechy) is the westernmost and largest historical region of the Czech Republic. Bohemia can also refer to a wider area consisting of the historical Lands of the Bohemian Crown ruled by the Bohem ...
and a doctor of law at the
Vienna University The University of Vienna (german: Universität Wien) is a public research university located in Vienna, Austria. It was founded by Duke Rudolph IV in 1365 and is the oldest university in the German-speaking world. With its long and rich histor ...
. His mother, Jenny Schiff (1864-1938), was an accomplished pianist, of Silesian and Hungarian descent. Popper's uncle was the Austrian philosopher
Josef Popper-Lynkeus Josef Popper-Lynkeus (21 February 1838 – 22 December 1921) was an Austrian scholar, writer, and inventor. Josef Popper was born in the Jewish quarter in Kolín, Bohemia (now Czech Republic). He was the uncle of Austrian-British philosopher Kar ...
. After establishing themselves in Vienna, the Poppers made a rapid social climb in Viennese society, as Popper's father became a partner in the law firm of Vienna's liberal mayor
Raimund Grübl Raimund Grübl (12 August 1847, Vienna – 12 May 1898, Vienna) was an Austrian lawyer and mayor of Vienna from 1894 to 1895. He is regarded as the last liberal Liberal or liberalism may refer to: Politics * a supporter of liberalism ** Libera ...
, and after Grübl's death in 1898 took over the business. Popper received his middle name after Raimund Grübl.Malachi Haim Hacohen. ''Karl Popper – The Formative Years, 1902–1945: Politics and Philosophy in Interwar Vienna.'' Cambridge: Cambridge University Press, 2001. pp. 10, 23, (In his autobiography, Popper erroneously recalls that Grübl's first name was Carl). His parents were close friends of
Sigmund Freud Sigmund Freud ( , ; born Sigismund Schlomo Freud; 6 May 1856 – 23 September 1939) was an Austrian neurologist and the founder of psychoanalysis, a clinical method for evaluating and treating pathologies explained as originating in conflicts i ...
's sister Rosa Graf. His father was a
bibliophile Bibliophilia or bibliophilism is the love of books. A bibliophile or bookworm is an individual who loves and frequently reads and/or collects books. Profile The classic bibliophile is one who loves to read, admire and collect books, often ama ...
who had 12,000–14,000 volumes in his personal libraryRaphael, F. ''The Great Philosophers'' London: Phoenix, p. 447, and took an interest in philosophy, the classics, and social and political issues. Popper inherited both the library and the disposition from him. Later, he would describe the atmosphere of his upbringing as having been "decidedly bookish". Popper left school at the age of 16 and attended lectures in mathematics, physics, philosophy, psychology and the history of music as a guest student at the University of Vienna. In 1919, Popper became attracted by
Marxism Marxism is a Left-wing politics, left-wing to Far-left politics, far-left method of socioeconomic analysis that uses a Materialism, materialist interpretation of historical development, better known as historical materialism, to understand S ...
and subsequently joined the Association of Socialist School Students. He also became a member of the Social Democratic Workers' Party of Austria, which was at that time a party that fully adopted the Marxist ideology. After the street battle in the Hörlgasse on 15 June 1919, when police shot eight of his unarmed party comrades, he turned away from what he saw as the philosopher
Karl Marx Karl Heinrich Marx (; 5 May 1818 – 14 March 1883) was a German philosopher, economist, historian, sociologist, political theorist, journalist, critic of political economy, and socialist revolutionary. His best-known titles are the 1848 ...
's
historical materialism Historical materialism is the term used to describe Karl Marx's theory of history. Marx locates historical change in the rise of class societies and the way humans labor together to make their livelihoods. For Marx and his lifetime collaborat ...
, abandoned the ideology, and remained a supporter of
social liberalism Social liberalism (german: Sozialliberalismus, es, socioliberalismo, nl, Sociaalliberalisme), also known as new liberalism in the United Kingdom, modern liberalism, or simply liberalism in the contemporary United States, left-liberalism ...
throughout his life. He worked in street construction for a short time but was unable to cope with the heavy labour. Continuing to attend university as a guest student, he started an apprenticeship as a cabinetmaker, which he completed as a journeyman. He was dreaming at that time of starting a daycare facility for children, for which he assumed the ability to make furniture might be useful. After that, he did voluntary service in one of
psychoanalyst PsychoanalysisFrom Greek: + . is a set of theories and therapeutic techniques"What is psychoanalysis? Of course, one is supposed to answer that it is many things — a theory, a research method, a therapy, a body of knowledge. In what might ...
Alfred Adler's clinics for children. In 1922, he did his
matura or its translated terms (''Mature'', ''Matur'', , , , , , ) is a Latin name for the secondary school exit exam or "maturity diploma" in various European countries, including Albania, Austria, Bosnia and Herzegovina, Bulgaria, Croatia, C ...
by way of a second chance education and finally joined the university as an ordinary student. He completed his examination as an elementary teacher in 1924 and started working at an after-school care club for socially endangered children. In 1925, he went to the newly founded ''Pädagogisches Institut'' and continued studying philosophy and psychology. Around that time he started courting Josefine Anna Henninger, who later became his wife. In 1928, Popper earned a doctorate in psychology, under the supervision of
Karl Bühler Karl Ludwig Bühler (27 May 1879 – 24 October 1963) was a German psychologist and linguist. In psychology he is known for his work in gestalt psychology, and he was one of the founders of the Würzburg School of psychology. In linguistics he ...
—with Moritz Schlick being the second chair of the
thesis committee A thesis ( : theses), or dissertation (abbreviated diss.), is a document submitted in support of candidature for an academic degree or professional qualification presenting the author's research and findings.International Standard ISO 7144: ...
. His dissertation was titled ''Zur Methodenfrage der Denkpsychologie'' (''On Questions of Method in the Psychology of Thinking''). In 1929, he obtained an authorisation to teach mathematics and physics in secondary school and began doing so. He married his colleague Josefine Anna Henninger (1906–1985) in 1930. Fearing the rise of
Nazism Nazism ( ; german: Nazismus), the common name in English for National Socialism (german: Nationalsozialismus, ), is the far-right totalitarian political ideology and practices associated with Adolf Hitler and the Nazi Party (NSDAP) i ...
and the threat of the ''
Anschluss The (, or , ), also known as the (, en, Annexation of Austria), was the annexation of the Federal State of Austria into the German Reich on 13 March 1938. The idea of an (a united Austria and Germany that would form a " Greater Germa ...
'', he started to use the evenings and the nights to write his first book ''Die beiden Grundprobleme der Erkenntnistheorie'' (''The Two Fundamental Problems of the Theory of Knowledge''). He needed to publish a book to get an academic position in a country that was safe for people of Jewish descent. In the end, he did not publish the two-volume work; but instead, a condensed version with some new material, as ''Logik der Forschung'' (''
The Logic of Scientific Discovery ''The Logic of Scientific Discovery'' is a 1959 book about the philosophy of science by the philosopher Karl Popper. Popper rewrote his book in English from the 1934 (imprint '1935') German original, titled ''Logik der Forschung. Zur Erkenntnisthe ...
'') in 1934. Here, he criticised psychologism, naturalism,
inductivism Inductivism is the traditional and still commonplace philosophy of scientific method to develop scientific theories.James Ladyman, ''Understanding Philosophy of Science'' (London & New York: Routledge, 2002), p5158 Inductivism aims to neutrally ...
, and
logical positivism Logical positivism, later called logical empiricism, and both of which together are also known as neopositivism, is a movement in Western philosophy whose central thesis was the verification principle (also known as the verifiability criterion o ...
, and put forth his theory of potential
falsifiability Falsifiability is a standard of evaluation of scientific theories and hypotheses that was introduced by the philosopher of science Karl Popper in his book '' The Logic of Scientific Discovery'' (1934). He proposed it as the cornerstone of a s ...
as the criterion demarcating science from non-science. In 1935 and 1936, he took unpaid leave to go to the United Kingdom for a study visit.


Academic life

In 1937, Popper finally managed to get a position that allowed him to emigrate to New Zealand, where he became lecturer in philosophy at Canterbury University College of the University of New Zealand in
Christchurch Christchurch ( ; mi, Ōtautahi) is the largest city in the South Island of New Zealand and the seat of the Canterbury Region. Christchurch lies on the South Island's east coast, just north of Banks Peninsula on Pegasus Bay. The Avon Rive ...
. It was here that he wrote his influential work ''
The Open Society and Its Enemies ''The Open Society and Its Enemies'' is a work on political philosophy by the philosopher Karl Popper, in which the author presents a "defence of the open society against its enemies", and offers a critique of theories of teleological historicism ...
''. In
Dunedin Dunedin ( ; mi, Ōtepoti) is the second-largest city in the South Island of New Zealand (after Christchurch), and the principal city of the Otago region. Its name comes from , the Scottish Gaelic name for Edinburgh, the capital of Scotland. Th ...
he met the Professor of Physiology John Carew Eccles and formed a lifelong friendship with him. In 1946, after the
Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposi ...
, he moved to the United Kingdom to become a
reader A reader is a person who reads. It may also refer to: Computing and technology * Adobe Reader (now Adobe Acrobat), a PDF reader * Bible Reader for Palm, a discontinued PDA application * A card reader, for extracting data from various forms of ...
in
logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the science of deductively valid inferences or of logical truths. It is a formal science investigating how conclusions follow from prem ...
and
scientific method The scientific method is an empirical method for acquiring knowledge that has characterized the development of science since at least the 17th century (with notable practitioners in previous centuries; see the article history of scientifi ...
at the
London School of Economics , mottoeng = To understand the causes of things , established = , type = Public research university , endowment = £240.8 million (2021) , budget = £391.1 milli ...
(LSE), a constituent School of the
University of London The University of London (UoL; abbreviated as Lond or more rarely Londin in post-nominals) is a federal public research university located in London, England, United Kingdom. The university was established by royal charter in 1836 as a degr ...
, where, three years later, in 1949, he was appointed professor of logic and scientific method. Popper was president of the
Aristotelian Society The Aristotelian Society for the Systematic Study of Philosophy, more generally known as the Aristotelian Society, is a philosophical society in London. History Aristotelian Society was founded at a meeting on 19 April 1880, at 17 Bloomsbury Squa ...
from 1958 to 1959. Popper retired from academic life in 1969, though he remained intellectually active for the rest of his life. In 1985, he returned to Austria so that his wife could have her relatives around her during the last months of her life; she died in November that year. After the
Ludwig Boltzmann Gesellschaft The Ludwig Boltzmann Gesellschaft (LBG) is an Austrian network of specialized research institutes that are not part of a university. It was founded in 1961 and named after physicist Ludwig Boltzmann. In 1999, the Ludwig Boltzmann Gesellschaft com ...
failed to establish him as the director of a newly founded branch researching the philosophy of science, he went back again to the United Kingdom in 1986, settling in
Kenley Kenley is an area within the London Borough of Croydon. Prior to its incorporation into Greater London in 1965 it was in the historic county of Surrey. It is situated south of Purley, east of Coulsdon, north of Caterham and Whyteleafe and w ...
, Surrey.


Death

Popper died of "complications of cancer, pneumonia and kidney failure" in Kenley at the age of 92 on 17 September 1994. He had been working continuously on his philosophy until two weeks before when he suddenly fell terminally ill. After cremation, his ashes were taken to Vienna and buried at Lainzer cemetery adjacent to the ORF Centre, where his wife Josefine Anna Popper (called "Hennie") had already been buried. Popper's estate is managed by his secretary and personal assistant Melitta Mew and her husband Raymond. Popper's manuscripts went to the
Hoover Institution The Hoover Institution (officially The Hoover Institution on War, Revolution, and Peace; abbreviated as Hoover) is an American public policy think tank and research institution that promotes personal and economic liberty, free enterprise, a ...
at
Stanford University Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is conside ...
, partly during his lifetime and partly as supplementary material after his death. Klagenfurt University has Popper's library, including his precious bibliophilia, as well as hard copies of the original Hoover material and microfilms of the supplementary material. The remaining parts of the estate were mostly transferred to The Karl Popper Charitable Trust. In October 2008 Klagenfurt University acquired the copyrights from the estate. Popper and his wife had chosen not to have children because of the circumstances of war in the early years of their marriage. Popper commented that this "was perhaps a cowardly but in a way a right decision".Edward Zerin: Karl Popper On God: The Lost Interview. ''Skeptic'' 6:2 (1998)


Honours and awards

Popper won many awards and honours in his field, including the Lippincott Award of the
American Political Science Association The American Political Science Association (APSA) is a professional association of political science students and scholars in the United States. Founded in 1903 in the Tilton Memorial Library (now Tilton Hall) of Tulane University in New Orle ...
, the Sonning Prize, the Otto Hahn Peace Medal of the United Nations Association of Germany in Berlin and fellowships in the Royal Society,
British Academy The British Academy is the United Kingdom's national academy for the humanities and the social sciences. It was established in 1902 and received its royal charter in the same year. It is now a fellowship of more than 1,000 leading scholars s ...
,
London School of Economics , mottoeng = To understand the causes of things , established = , type = Public research university , endowment = £240.8 million (2021) , budget = £391.1 milli ...
,
King's College London King's College London (informally King's or KCL) is a public research university located in London, England. King's was established by royal charter in 1829 under the patronage of King George IV and the Duke of Wellington. In 1836, King's ...
, Darwin College,
Cambridge Cambridge ( ) is a university city and the county town in Cambridgeshire, England. It is located on the River Cam approximately north of London. As of the 2021 United Kingdom census, the population of Cambridge was 145,700. Cambridge bec ...
, Austrian Academy of Sciences and Charles University, Prague. Austria awarded him the
Grand Decoration of Honour in Gold for Services to the Republic of Austria The Decoration of Honour for Services to the Republic of Austria (german: Ehrenzeichen für Verdienste um die Republik Österreich) is a state decoration of the Republic of Austria. It is divided into 15 classes and is the highest award in the A ...
in 1986, and the Federal Republic of Germany its Grand Cross with Star and Sash of the Order of Merit, and the peace class of the Order
Pour le Mérite The ' (; , ) is an order of merit (german: Verdienstorden) established in 1740 by King Frederick II of Prussia. The was awarded as both a military and civil honour and ranked, along with the Order of the Black Eagle, the Order of the Red Eag ...
. He received the Humanist Laureate Award from the International Academy of Humanism. He was
knighted A knight is a person granted an honorary title of knighthood by a head of state (including the Pope) or representative for service to the monarch, the church or the country, especially in a military capacity. Knighthood finds origins in the G ...
by
Queen Elizabeth II Elizabeth II (Elizabeth Alexandra Mary; 21 April 1926 – 8 September 2022) was Queen of the United Kingdom and other Commonwealth realms from 6 February 1952 until her death in 2022. She was queen regnant of 32 sovereign states during ...
in 1965, and was elected a Fellow of the
Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
in 1976. He was invested with the Insignia of a
Companion of Honour The Order of the Companions of Honour is an order of the Commonwealth realms. It was founded on 4 June 1917 by King George V as a reward for outstanding achievements. Founded on the same date as the Order of the British Empire, it is sometimes ...
in 1982. Other awards and recognition for Popper included the City of Vienna Prize for the Humanities (1965), Karl Renner Prize (1978),
Austrian Decoration for Science and Art The Austrian Decoration for Science and Art (german: Österreichisches Ehrenzeichen für Wissenschaft und Kunst) is a state decoration of the Republic of Austria and forms part of the Austrian national honours system. History The "Austrian ...
(1980), Dr. Leopold Lucas Prize of the
University of Tübingen The University of Tübingen, officially the Eberhard Karl University of Tübingen (german: Eberhard Karls Universität Tübingen; la, Universitas Eberhardina Carolina), is a public research university located in the city of Tübingen, Baden-W ...
(1980), Ring of Honour of the City of Vienna (1983) and the Premio Internazionale of the Italian Federico Nietzsche Society (1988). In 1989, he was the first awarded the Prize International Catalonia for "his work to develop cultural, scientific and human values all around the world". In 1992, he was awarded the
Kyoto Prize in Arts and Philosophy The Kyoto Prize in Arts and Philosophy is awarded once a year by the Inamori Foundation for lifetime achievements in the arts and philosophy. The Prize is one of three Kyoto Prize categories; the others are the Kyoto Prize in Advanced Technolog ...
for "symbolising the open spirit of the 20th century" and for his "enormous influence on the formation of the modern intellectual climate".


Philosophy


Background to Popper's ideas

Popper's rejection of
Marxism Marxism is a Left-wing politics, left-wing to Far-left politics, far-left method of socioeconomic analysis that uses a Materialism, materialist interpretation of historical development, better known as historical materialism, to understand S ...
during his teenage years left a profound mark on his thought. He had at one point joined a socialist association, and for a few months in 1919 considered himself a
communist Communism (from Latin la, communis, lit=common, universal, label=none) is a far-left sociopolitical, philosophical, and economic ideology and current within the socialist movement whose goal is the establishment of a communist society, ...
. Although it is known that Popper worked as an office boy at the communist headquarters, whether or not he ever became a member of the Communist Party is unclear. During this time he became familiar with the Marxist view of economics,
class conflict Class conflict, also referred to as class struggle and class warfare, is the political tension and economic antagonism that exists in society because of socio-economic competition among the social classes or between rich and poor. The forms ...
, and history. Although he quickly became disillusioned with the views expounded by Marxists, his flirtation with the ideology led him to distance himself from those who believed that spilling blood for the sake of a revolution was necessary. He then took the view that when it came to sacrificing human lives, one was to think and act with extreme prudence. The failure of democratic parties to prevent fascism from taking over Austrian politics in the 1920s and 1930s traumatised Popper. He suffered from the direct consequences of this failure since events after the ''
Anschluss The (, or , ), also known as the (, en, Annexation of Austria), was the annexation of the Federal State of Austria into the German Reich on 13 March 1938. The idea of an (a united Austria and Germany that would form a " Greater Germa ...
'' (the annexation of
Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...
by the
German Reich German ''Reich'' (lit. German Realm, German Empire, from german: Deutsches Reich, ) was the constitutional name for the German nation state that existed from 1871 to 1945. The ''Reich'' became understood as deriving its authority and sovereignty ...
in 1938) forced him into permanent exile. His most important works in the field of
social science Social science is one of the branches of science, devoted to the study of societies and the relationships among individuals within those societies. The term was formerly used to refer to the field of sociology, the original "science of s ...
—''
The Poverty of Historicism ''The Poverty of Historicism'' is a 1944 book by the philosopher Karl Popper (revised in 1957), in which the author argues that the idea of historicism is dangerous and bankrupt. Publication ''The Poverty of Historicism'' was first written as a ...
'' (1944) and ''
The Open Society and Its Enemies ''The Open Society and Its Enemies'' is a work on political philosophy by the philosopher Karl Popper, in which the author presents a "defence of the open society against its enemies", and offers a critique of theories of teleological historicism ...
'' (1945)—were inspired by his reflection on the events of his time and represented, in a sense, a reaction to the prevalent
totalitarian Totalitarianism is a form of government and a political system that prohibits all opposition parties, outlaws individual and group opposition to the state and its claims, and exercises an extremely high if not complete degree of control and reg ...
ideologies that then dominated Central European politics. His books defended
democratic liberalism Democratic liberalism aims to reach a synthesis of democracy which is the participation of the people in the power and liberalism, a political and/or social philosophy advocating the freedom of the individual. It arose after World War I (with mos ...
as a social and
political philosophy Political philosophy or political theory is the philosophical study of government, addressing questions about the nature, scope, and legitimacy of public agents and institutions and the relationships between them. Its topics include politics, ...
. They also represented extensive critiques of the philosophical presuppositions underpinning all forms of
totalitarianism Totalitarianism is a form of government and a political system that prohibits all opposition parties, outlaws individual and group opposition to the state and its claims, and exercises an extremely high if not complete degree of control and regu ...
. Popper believed that there was a contrast between the theories of
Sigmund Freud Sigmund Freud ( , ; born Sigismund Schlomo Freud; 6 May 1856 – 23 September 1939) was an Austrian neurologist and the founder of psychoanalysis, a clinical method for evaluating and treating pathologies explained as originating in conflicts i ...
and Alfred Adler, which he considered non-scientific, and
Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theor ...
's
theory of relativity The theory of relativity usually encompasses two interrelated theories by Albert Einstein: special relativity and general relativity, proposed and published in 1905 and 1915, respectively. Special relativity applies to all physical phenomena in ...
which set off the revolution in
physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which ...
in the early 20th century. Popper thought that Einstein's theory, as a theory properly grounded in scientific thought and method, was highly "risky", in the sense that it was possible to deduce consequences from it which differed considerably from those of the then-dominant
Newtonian physics Classical mechanics is a physical theory describing the motion of macroscopic objects, from projectiles to parts of machinery, and astronomical objects, such as spacecraft, planets, stars, and galaxies. For objects governed by classical mec ...
; one such prediction, that gravity could deflect light, was verified by Eddington's experiments in 1919. In contrast he thought that nothing could, even in principle, falsify psychoanalytic theories. He thus came to the conclusion that they had more in common with primitive myths than with genuine science. This led Popper to conclude that what was regarded as the remarkable strengths of psychoanalytical theories were actually their weaknesses. Psychoanalytical theories were crafted in a way that made them able to refute any criticism and to give an explanation for every possible form of human behaviour. The nature of such theories made it impossible for any criticism or experiment—even in principle—to show them to be false. When Popper later tackled the
problem of demarcation In philosophy of science and epistemology, the demarcation problem is the question of how to distinguish between science and non-science. It examines the boundaries between science, pseudoscience, and other products of human activity, like art ...
in the philosophy of science, this conclusion led him to posit that the strength of a scientific theory lies in its both being susceptible to falsification, and not actually being falsified by criticism made of it. He considered that if a theory cannot, in principle, be falsified by criticism, it is not a scientific theory.


Philosophy of science


Falsifiability and the problem of demarcation

Popper coined the term "critical rationalism" to describe his philosophy. Popper rejected the empiricist view (following from Kant) that basic statements are infallible; rather, according to Popper, they are descriptions in relation to a theoretical framework. Concerning the method of science, the term "critical rationalism" indicates his rejection of classical
empiricism In philosophy, empiricism is an epistemological theory that holds that knowledge or justification comes only or primarily from sensory experience. It is one of several views within epistemology, along with rationalism and skepticism. Empir ...
, and the classical observationalist-inductivist account of science that had grown out of it. Popper argued strongly against the latter, holding that
scientific theories A scientific theory is an explanation of an aspect of the natural world and universe that has been repeatedly tested and corroborated in accordance with the scientific method, using accepted protocols of observation, measurement, and evaluatio ...
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 to solve problems that have arisen in specific historico-cultural settings. Logically, no number of positive outcomes at the level of experimental testing can confirm a scientific theory, but a single counterexample is logically decisive; it shows the theory, from which the implication is derived, to be false. Popper's account of the logical asymmetry between verification and
falsifiability Falsifiability is a standard of evaluation of scientific theories and hypotheses that was introduced by the philosopher of science Karl Popper in his book '' The Logic of Scientific Discovery'' (1934). He proposed it as the cornerstone of a s ...
lies at the heart of his philosophy of science. It also inspired him to take falsifiability as his criterion of
demarcation Demarcation is the act of creating a boundary around a place or thing. Demarcation may also refer to: *Demarcation line, a temporary border between the countries *Demarcation problem, the question of which practices of doing science permit the re ...
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 PsychoanalysisFrom Greek: + . is a set of theories and therapeutic techniques"What is psychoanalysis? Of course, one is supposed to answer that it is many things — a theory, a research method, a therapy, a body of knowledge. In what might ...
and contemporary
Marxism Marxism is a Left-wing politics, left-wing to Far-left politics, far-left method of socioeconomic analysis that uses a Materialism, materialist interpretation of historical development, better known as historical materialism, to understand S ...
to scientific status, on the basis that their theories are not falsifiable. To say that a given statement (e.g., the statement of a law of some scientific theory)—call it "T"—is "
falsifiable Falsifiability is a standard of evaluation of scientific theories and hypotheses that was introduced by the philosopher of science Karl Popper in his book '' The Logic of Scientific Discovery'' (1934). He proposed it as the cornerstone of a so ...
" does not mean that "T" is false. It means only that the background knowledge about existing technologies, which exists before and independently of the theory, allows the imagination or conceptualization of observations that are in contradiction with the theory. It is only required that these contradictory observations can potentially be observed with existing technologies—the observations must be inter-subjective. This is the material requirement of falsifiability. Alan Chalmers gives "The brick fell upward when released" as an example of an imaginary observation that shows that Newton's law of gravitation is falsifiable. In ''All Life is Problem Solving'', Popper sought to explain the apparent progress of scientific knowledge—that is, 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. With only falsifications being possible logically, how can we explain the
growth of knowledge In Karl Popper's philosophy, the main problem of methodology and philosophy of science is to explain and promote the growth of knowledge. To this purpose, Popper advocated his theory of falsifiability, testability and testing. He wrote in ''The Log ...
? In Popper's view, the advance of scientific knowledge is an ''evolutionary'' process characterised by his formula: \mathrm_1 \rightarrow \mathrm_1 \rightarrow \mathrm_1 \rightarrow \mathrm_2. \, In response to a given problem situation (\mathrm_1), a number of competing conjectures, or tentative theories (\mathrm), are systematically subjected to the most rigorous attempts at falsification possible. This process, error elimination (\mathrm), performs a similar function for science that
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
performs for
biological evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation t ...
. 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 (\mathrm_1). 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, over many generations, produced 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 (\mathrm_2). For Popper, it is in the interplay between the tentative theories (conjectures) and error elimination (refutation) that scientific knowledge advances toward greater and greater problems; in a process very much akin to the interplay between genetic variation and natural selection. Popper also wrote extensively against the famous
Copenhagen interpretation The Copenhagen interpretation is a collection of views about the meaning of quantum mechanics, principally attributed to Niels Bohr and Werner Heisenberg. It is one of the oldest of numerous proposed interpretations of quantum mechanics, as feat ...
of
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
. He strongly disagreed with
Niels Bohr Niels Henrik David Bohr (; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922 ...
's
instrumentalism In philosophy of science and in epistemology, instrumentalism is a methodological view that ideas are useful instruments, and that the worth of an idea is based on how effective it is in explaining and predicting phenomena. According to instrumenta ...
and supported
Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theor ...
's realist approach to scientific theories about the universe. Popper's falsifiability resembles
Charles Peirce Charles Sanders Peirce ( ; September 10, 1839 – April 19, 1914) was an American philosopher, logician, mathematician and scientist who is sometimes known as "the father of pragmatism". Educated as a chemist and employed as a scientist for ...
's nineteenth-century
fallibilism Originally, fallibilism (from Medieval Latin: ''fallibilis'', "liable to err") is the philosophical principle that propositions can be accepted even though they cannot be conclusively proven or justified,Haack, Susan (1979)"Fallibilism and Nece ...
. In ''Of Clocks and Clouds'' (1966), Popper remarked that he wished he had known of Peirce's work earlier.


Falsification and the problem of induction

Among his contributions to philosophy is his claim to have solved the philosophical
problem of induction First formulated by David Hume, the problem of induction questions our reasons for believing that the future will resemble the past, or more broadly it questions predictions about unobserved things based on previous observations. This inferen ...
. 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. Nor is it rational according to Popper to make instead the more complex assumption that the sun will rise until a given day, but will stop doing so the day after, or similar statements with additional conditions. 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 the 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 its falsity can be detected as easily as possible. Popper agreed with
David Hume David Hume (; born David Home; 7 May 1711 NS (26 April 1711 OS) – 25 August 1776) Cranston, Maurice, and Thomas Edmund Jessop. 2020 999br>David Hume" '' Encyclopædia Britannica''. Retrieved 18 May 2020. was a Scottish Enlightenment ph ...
that there is often a psychological belief that the sun will rise tomorrow and that there is no logical justification for the supposition that it will, simply because it always has in the past. Popper writes,


Rationality

Popper held that rationality is not restricted to the realm of empirical or scientific theories, but that it is merely a special case of the general method of criticism, the method of finding and eliminating contradictions in knowledge without ad-hoc measures. According to this view, rational discussion about metaphysical ideas, about moral values and even about purposes is possible. Popper's student W.W. Bartley III tried to radicalise this idea and made the controversial claim that not only can criticism go beyond empirical knowledge but that everything can be rationally criticised. To Popper, who was an anti-
justificationist Critical rationalism is an epistemological philosophy advanced by Karl Popper on the basis that, if a statement cannot be logically deduced (from what is known), it might nevertheless be possible to logically falsify it. Following David Hume, Hum ...
, traditional philosophy is misled by the false principle of sufficient reason. 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 scrutinised. It is not the goal to bless theories with claims of certainty or justification, but to eliminate errors in them. He writes,


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 The philosophy of mathematics is the branch of philosophy that studies the assumptions, foundations, and implications of mathematics. It aims to understand the nature and methods of mathematics, and find out the place of mathematics in people' ...
. His idea was that a number statement such as "2 apples + 2 apples = 4 apples" can be taken in two senses. In its
pure mathematics Pure mathematics is the study of mathematical concepts independently of any application outside mathematics. These concepts may originate in real-world concerns, and the results obtained may later turn out to be useful for practical applications, ...
sense, "2 + 2 = 4" is logically true and cannot be refuted. Contrastingly, in its
applied mathematics Applied mathematics is the application of mathematical methods by different fields such as physics, engineering, medicine, biology, finance, business, computer science, and industry. Thus, applied mathematics is a combination of mathemati ...
sense of it describing the physical behaviour of apples, it can be falsified. This can be done by placing two apples in a container, then proceeding to place another two apples in the same container. If there are five, three, or a number of apples that is not four in said container, the theory that "2 apples + 2 apples = 4 apples" is shown to be false. On the contrary, if there are four apples in the container, the theory of numbers is shown to be applicable to reality.


Political philosophy

In ''
The Open Society and Its Enemies ''The Open Society and Its Enemies'' is a work on political philosophy by the philosopher Karl Popper, in which the author presents a "defence of the open society against its enemies", and offers a critique of theories of teleological historicism ...
'' and ''
The Poverty of Historicism ''The Poverty of Historicism'' is a 1944 book by the philosopher Karl Popper (revised in 1957), in which the author argues that the idea of historicism is dangerous and bankrupt. Publication ''The Poverty of Historicism'' was first written as a ...
'', Popper developed a critique of
historicism Historicism is an approach to explaining the existence of phenomena, especially social and cultural practices (including ideas and beliefs), by studying their history, that is, by studying the process by which they came about. The term is widely ...
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 is a political system characterized by the rejection of political plurality, the use of strong central power to preserve the political ''status quo'', and reductions in the rule of law, separation of powers, and democratic voti ...
and
totalitarianism Totalitarianism is a form of government and a political system that prohibits all opposition parties, outlaws individual and group opposition to the state and its claims, and exercises an extremely high if not complete degree of control and regu ...
. 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 his early years Popper was impressed by Marxism, whether of Communists or socialists. An event that happened in 1919 had a profound effect on him: During a riot, caused by the Communists, the police shot several unarmed people, including some of Popper's friends, when they tried to free party comrades from prison. The riot had, in fact, been part of a plan by which leaders of the Communist party with connections to Béla Kun tried to take power by a coup; Popper did not know about this at that time. However, he knew that the riot instigators were swayed by the Marxist doctrine that class struggle would produce vastly more dead men than the inevitable revolution brought about as quickly as possible, and so had no scruples to put the life of the rioters at risk to achieve their selfish goal of becoming the future leaders of the working class. This was the start of his later criticism of historicism. Popper began to reject Marxist historicism, which he associated with questionable means, and later
socialism Socialism is a left-wing economic philosophy and movement encompassing a range of economic systems characterized by the dominance of social ownership of the means of production as opposed to private ownership. As a term, it describes th ...
, which he associated with placing equality before freedom (to the possible disadvantage of equality). Popper said that he was a socialist for "several years", and maintained an interest in egalitarianism, but abandoned it as a whole because socialism was a "beautiful dream", but, just like egalitarianism, it was incompatible with individual liberty. Popper initially saw totalitarianism as exclusively right-wing in nature, although as early as 1945 in ''The Open Society'' he was describing Communist parties as giving a weak opposition to fascism due to shared historicism with fascism. Over time, primarily in defence of liberal democracy, Popper began to see Soviet-type communism as a form of totalitarianism, and viewed the main issue of the
Cold War The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because t ...
as not capitalism versus socialism, but democracy versus totalitarianism. In 1957, Popper would dedicate ''The Poverty of Historicism'' to "memory of the countless men, women and children of all creeds or nations or races who fell victims to the fascist and communist belief in Inexorable Laws of Historical Destiny." In 1947, Popper co-founded the
Mont Pelerin Society The Mont Pelerin Society (MPS) is an international organization composed of economists, philosophers, historians, intellectuals and business leaders.Michael Novak, 'The Moral Imperative of a Free Economy', in '' The 4% Solution: Unleashing the E ...
, with
Friedrich Hayek Friedrich August von Hayek ( , ; 8 May 189923 March 1992), often referred to by his initials F. A. Hayek, was an Austrian–British economist, legal theorist and philosopher who is best known for his defense of classical liberalism. Hayek ...
,
Milton Friedman Milton Friedman (; July 31, 1912 – November 16, 2006) was an American economist and statistician who received the 1976 Nobel Memorial Prize in Economic Sciences for his research on consumption analysis, monetary history and theory and the ...
,
Ludwig von Mises Ludwig Heinrich Edler von Mises (; 29 September 1881 – 10 October 1973) was an Austrian School economist, historian, logician, and sociologist. Mises wrote and lectured extensively on the societal contributions of classical liberalism. He is ...
and others, although he did not fully agree with the think tank's charter and ideology. Specifically, he unsuccessfully recommended that socialists should be invited to participate, and that emphasis should be put on a hierarchy of humanitarian values rather than advocacy of a free market as envisioned by
classical liberalism Classical liberalism is a political tradition and a branch of liberalism that advocates free market and laissez-faire economics; civil liberties under the rule of law with especial emphasis on individual autonomy, limited government, e ...
.


The paradox of tolerance

Although Popper was an advocate of toleration, he also warned against unlimited tolerance. In ''
The Open Society and Its Enemies ''The Open Society and Its Enemies'' is a work on political philosophy by the philosopher Karl Popper, in which the author presents a "defence of the open society against its enemies", and offers a critique of theories of teleological historicism ...
'', he argued:


The "conspiracy theory of society"

Popper criticized what he termed the "conspiracy theory of society," the view that powerful people or groups, godlike in their efficacy, are responsible for purposely bringing about all the ills of society. This view cannot be right, Popper argued, because "nothing ever comes off exactly as intended." According to philosopher David Coady, "Popper has often been cited by critics of conspiracy theories, and his views on the topic continue to constitute an orthodoxy in some circles." However, philosopher Charles Pigden has pointed out that Popper's argument only applies to a very extreme kind of conspiracy theory, not to conspiracy theories generally.


Metaphysics


Truth

As early as 1934, Popper wrote of the search for truth as "one of the strongest motives for scientific discovery." Still, he describes in ''Objective Knowledge'' (1972) early concerns about the much-criticised notion of truth as correspondence. Then came the
semantic theory of truth 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 deflati ...
formulated by the logician
Alfred Tarski Alfred Tarski (, born Alfred Teitelbaum;School of Mathematics and Statistics, University of St Andrews ''School of Mathematics and Statistics, University of St Andrews''. January 14, 1901 – October 26, 1983) was a Polish-American logician a ...
and published in 1933. Popper wrote of learning in 1935 of the consequences of Tarski's theory, to his intense joy. The theory met critical objections to
truth Truth is the property of being in accord with fact or reality.Merriam-Webster's Online Dictionarytruth 2005 In everyday language, truth is typically ascribed to things that aim to represent reality or otherwise correspond to it, such as belief ...
as correspondence and thereby rehabilitated it. The theory also seemed, in Popper's eyes, to support
metaphysical realism Philosophical realism is usually not treated as a position of its own but as a stance towards other subject matters. Realism about a certain kind of thing (like numbers or morality) is the thesis that this kind of thing has ''mind-independent ex ...
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 In logic and linguistics, a metalanguage is a language used to describe another language, often called the ''object language''. Expressions in a metalanguage are often distinguished from those in the object language by the use of italics, quota ...
. So, for example, the sentence "Snow is white" is true if and only if snow is white. Although many philosophers have interpreted, and continue to interpret, Tarski's theory as a deflationary theory, Popper refers to it as a theory in which "is true" is replaced with " corresponds to the facts". He bases this interpretation on the fact that examples such as the one described above refer to two things: assertions and the facts to which they refer. He identifies Tarski's formulation of the truth conditions of sentences as the introduction of a "metalinguistic predicate" and distinguishes the following cases: # "John called" is true. # "It is true that John called." The first case belongs to the metalanguage whereas the second is more likely to belong to the object language. Hence, "it is true that" possesses the logical status of a redundancy. "Is true", on the other hand, is a predicate necessary for making general observations such as "John was telling the truth about Phillip." Upon this basis, along with that of the logical content of assertions (where logical content is inversely proportional to probability), Popper went on to develop his important notion of
verisimilitude In philosophy, verisimilitude (or truthlikeness) is the notion that some propositions are closer to being true than other propositions. The problem of verisimilitude is the problem of articulating what it takes for one false theory to be clo ...
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 emphasises forcefully, has nothing to do with "subjective probabilities" or other merely "epistemic" considerations. The simplest mathematical formulation that Popper gives of this concept can be found in the tenth chapter of ''Conjectures and Refutations''. Here he defines it as: : \mathit(a)=\mathit_v(a)-\mathit_f(a) \, where \mathit(a) is the verisimilitude of ''a'', \mathit_v(a) is a measure of the content of the truth of ''a'', and \mathit_f(a) is a measure of the content of the falsity of ''a''. Popper's original attempt to define not just verisimilitude, but an actual measure of it, turned out to be inadequate. However, it inspired a wealth of new attempts.


Popper's three worlds

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: 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's path is the product of individual animals, and thus has an existence and is evolution independent of any individually known 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, comparably 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, such as
Daniel Dennett Daniel Clement Dennett III (born March 28, 1942) 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 relat ...
, have not embraced Popper's Three World conjecture, mostly due to its resemblance to mind–body dualism.


Origin and evolution of life

The
creation–evolution controversy Recurring cultural, political, and theological rejection of evolution by religious groups (sometimes termed the creation–evolution controversy, the creation vs. evolution debate or the origins debate) exists regarding the origins of the Ea ...
in the United States raises the issue of whether creationistic ideas may be legitimately called science and whether evolution itself may be legitimately called science. In the debate, both sides and even courts in their decisions have frequently invoked Popper's criterion of falsifiability (see
Daubert standard In United States federal law, the ''Daubert'' standard is a rule of evidence regarding the admissibility of expert witness testimony. A party may raise a ''Daubert'' motion, a special motion ''in limine'' raised before or during trial, to exclude ...
). 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 is a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others, stating that all species of organisms arise and develop through the natural selection of small, inherited variations tha ...
is not a testable scientific theory, but a
metaphysical Metaphysics is the branch of philosophy that studies the fundamental nature of reality, the first principles of being, identity and change, space and time, causality, necessity, and possibility. It includes questions about the nature of conscio ...
research program—a possible framework for testable scientific theories." He continued: He also noted that
theism Theism is broadly defined as the belief in the existence of a supreme being or deities. In common parlance, or when contrasted with '' deism'', the term often describes the classical conception of God that is found in monotheism (also referr ...
, presented as explaining adaptation, "was worse than an open admission of failure, for it created the impression that an ultimate explanation had been reached". Popper later said: In 1974, regarding DNA and the
origin of life In biology, abiogenesis (from a- 'not' + Greek bios 'life' + genesis 'origin') or the origin of life is the natural process by which life has arisen from non-living matter, such as simple organic compounds. The prevailing scientific hypothes ...
he said: He explained that the difficulty of testing had led some people to describe natural selection as a tautology, and that he too had in the past described the theory as "almost tautological", and had tried to explain how the theory could be untestable (as is a tautology) and yet of great scientific interest: Popper summarised 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 stresses at the beginning of ''Logic of Scientific Discovery'' that "the last thing I wish to do, however, is to advocate another dogma" and that "what is to be called a 'science' and who is to be called a 'scientist' must always remain a matter of convention or decision." He quotes Menger's dictum that "Definitions are dogmas; only the conclusions drawn from them can afford us any new insight" and notes that different definitions of science can be rationally debated and compared: Popper had his 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 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. He said that evolution of the genotype must, as the creationists say, work in a goal-directed way but disagreed with their view that it must necessarily be the hand of god that imposes these goals onto the stage of life. Instead, he formulated the spearhead model of
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
, a version of genetic pluralism. According to this model, 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 An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudop ...
. This control organ plays a special role in evolution—it is the "spearhead of evolution". The 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 In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (biology), morphology or physical form and structure, its Developmental biology, developmental proc ...
. Popper postulates that such purely behavioural 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 behavioural monster". After behaviour 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" or "active Darwinism" (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). Popper was a key figure encouraging patent lawyer Günter Wächtershäuser to publish his
iron–sulfur world hypothesis The iron–sulfur world hypothesis is a set of proposals for the origin of life and the early evolution of life advanced in a series of articles between 1988 and 1992 by Günter Wächtershäuser, a Munich patent lawyer with a degree in chemistry, ...
on
abiogenesis In biology, abiogenesis (from a- 'not' + Greek bios 'life' + genesis 'origin') or the origin of life is the natural process by which life has arisen from non-living matter, such as simple organic compounds. The prevailing scientific hypothes ...
and his criticism of "soup" theory. About the creation-evolution controversy itself, Popper initially wrote that he considered it with a footnote to the effect that he In his later work, however, when he had developed his own "spearhead model" and "active Darwinism" theories, Popper revised this view and found some validity in the controversy:


Free will

Popper and John Eccles speculated on the problem of
free will Free will is the capacity of agents to choose between different possible courses of action unimpeded. Free will is closely linked to the concepts of moral responsibility, praise, culpability, sin, and other judgements which apply only to ac ...
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 second
Arthur Holly Compton Arthur Holly Compton (September 10, 1892 – March 15, 1962) was an American physicist who won the Nobel Prize in Physics in 1927 for his 1923 discovery of the Compton effect, which demonstrated the particle nature of electromagnetic radi ...
Memorial Lecture in 1965, Popper revisited the idea of quantum indeterminacy 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 criticised Compton's idea of amplified quantum events affecting the decision. He wrote: 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, saying, "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:


Religion and God

In an interview that Popper gave in 1969 with the condition that it should be kept secret until after his death, he summarised his position on God as follows: "I don't know whether God exists or .... Some forms of atheism are arrogant and ignorant and should be rejected, but
agnosticism Agnosticism is the view or belief that the existence of God, of the divine or the supernatural is unknown or unknowable. (page 56 in 1967 edition) Another definition provided is the view that "human reason is incapable of providing sufficien ...
—to admit that we don't know and to search—is all right. ... When I look at what I call the gift of life, I feel a gratitude which is in tune with some religious ideas of God. However, the moment I even speak of it, I am embarrassed that I may do something wrong to God in talking about God." He objected to organised religion, saying "it tends to use the name of God in vain", noting the danger of fanaticism because of religious conflicts: "The whole thing goes back to myths which, though they may have a kernel of truth, are untrue. Why then should the Jewish myth be true and the Indian and Egyptian myths not be true?" In a letter unrelated to the interview, he stressed his tolerant attitude: "Although I am not for religion, I do think that we should show respect for anybody who believes honestly."


Influence

Popper helped to establish the
philosophy of science Philosophy of science is a branch of philosophy concerned with the foundations, methods, and implications of science. The central questions of this study concern what qualifies as science, the reliability of scientific theories, and the ultim ...
as an autonomous discipline within philosophy, both through his own prolific and influential works and through his influence on his contemporaries and students. In 1946, Popper founded the Department of Philosophy, Logic and Scientific Method at the
London School of Economics , mottoeng = To understand the causes of things , established = , type = Public research university , endowment = £240.8 million (2021) , budget = £391.1 milli ...
(LSE) and there lectured and influenced both Imre Lakatos and
Paul Feyerabend Paul Karl Feyerabend (; January 13, 1924 – February 11, 1994) 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 (195 ...
, two of the foremost philosophers of science in the next generation. (Lakatos significantly modified Popper's position,Site on Lakatos/Popper John Kadvany, PhD
/ref> and Feyerabend repudiated it entirely, but the work of both was deeply influenced by Popper and engaged with many of the problems that Popper set.) Although there is some dispute as to the matter of influence, Popper had a longstanding and close friendship with economist
Friedrich Hayek Friedrich August von Hayek ( , ; 8 May 189923 March 1992), often referred to by his initials F. A. Hayek, was an Austrian–British economist, legal theorist and philosopher who is best known for his defense of classical liberalism. Hayek ...
, who was also brought to LSE from Vienna. Each found support and similarities in the 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 (, born Alfred Teitelbaum;School of Mathematics and Statistics, University of St Andrews ''School of Mathematics and Statistics, University of St Andrews''. January 14, 1901 – October 26, 1983) was a Polish-American logician a ...
." Popper dedicated his ''Conjectures and Refutations'' to Hayek. For his part, Hayek dedicated a collection of papers, ''Studies in Philosophy, Politics, and Economics'', to Popper, and in 1982 said, "ever since his ''Logik der Forschung'' first came out in 1934, I have been a complete adherent to his general theory of methodology." Popper also had long and mutually influential friendships with art historian
Ernst Gombrich Sir Ernst Hans Josef Gombrich (; ; 30 March 1909 – 3 November 2001) was an Austrian-born art historian who, after settling in England in 1936, became a naturalised British citizen in 1947 and spent most of his working life in the United Ki ...
, biologist
Peter Medawar Sir Peter Brian Medawar (; 28 February 1915 – 2 October 1987) was a Brazilian-British biologist and writer, whose works on graft rejection and the discovery of acquired immune tolerance have been fundamental to the medical practice of tissu ...
, and neuroscientist John Carew Eccles. The German jurist
Reinhold Zippelius Reinhold Zippelius (born 19 May 1928) is a German jurist and law scholar. Now retired, he was formerly the professor of the Philosophy of law and Public law at the University of Erlangen-Nuremberg. Life and career Reinhold Walter Zippelius was ...
uses Popper's method of "trial and error" in his legal philosophy.
Peter Medawar Sir Peter Brian Medawar (; 28 February 1915 – 2 October 1987) was a Brazilian-British biologist and writer, whose works on graft rejection and the discovery of acquired immune tolerance have been fundamental to the medical practice of tissu ...
called him "incomparably the greatest philosopher of science that has ever been". 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 LSE was
George Soros George Soros ( name written in eastern order), (born György Schwartz, August 12, 1930) is a Hungarian-American businessman and philanthropist. , he had a net worth of US$8.6 billion, Note that this site is updated daily. having donated mo ...
, who later became a billionaire investor and among whose philanthropic foundations is the
Open Society Institute Open Society Foundations (OSF), formerly the Open Society Institute, is a grantmaking network founded and chaired by business magnate George Soros. Open Society Foundations financially supports civil society groups around the world, with a st ...
, a think-tank named in honour of Popper's ''
The Open Society and Its Enemies ''The Open Society and Its Enemies'' is a work on political philosophy by the philosopher Karl Popper, in which the author presents a "defence of the open society against its enemies", and offers a critique of theories of teleological historicism ...
''. Soros revised his own philosophy, differing from some of Popper's
epistemological Epistemology (; ), or the theory of knowledge, is the branch of philosophy concerned with knowledge. Epistemology is considered a major subfield of philosophy, along with other major subfields such as ethics, logic, and metaphysics. Episte ...
assumptions, in a lecture entitled ''Open Society'' given at
Central European University Central European University (CEU) is a private research university accredited in Austria, Hungary, and the United States, with campuses in Vienna and Budapest. The university is known for its highly intensive programs in the social science ...
on 28 October 2009:


Criticism

Most criticisms of Popper's philosophy are of the falsification, or error elimination, element in his account of problem solving. Popper presents falsifiability as both an ideal and as an important principle in a 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 recommended as an essential principle of methodology that, if enacted by a system or community, will 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, later called logical empiricism, and both of which together are also known as neopositivism, is a movement in Western philosophy whose central thesis was the verification principle (also known as the verifiability criterion o ...
, the followers of which mistook his aims for their own. The Quine–Duhem thesis argues that it is 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 is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 time ...
: when the motion of
Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus ( Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of ...
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
naive falsificationism Falsifiability is a standard of evaluation of scientific theories and hypotheses that was introduced by the philosopher of science Karl Popper in his book ''The Logic of Scientific Discovery'' (1934). He proposed it as the cornerstone of a sol ...
in Chapters 3 and 4 of ''
The Logic of Scientific Discovery ''The Logic of Scientific Discovery'' is a 1959 book about the philosophy of science by the philosopher Karl Popper. Popper rewrote his book in English from the 1934 (imprint '1935') German original, titled ''Logik der Forschung. Zur Erkenntnisthe ...
''. The philosopher
Thomas Kuhn Thomas Samuel Kuhn (; July 18, 1922 – June 17, 1996) was an American philosopher of science whose 1962 book '' The Structure of Scientific Revolutions'' was influential in both academic and popular circles, introducing the term ''paradig ...
writes in ''
The Structure of Scientific Revolutions ''The Structure of Scientific Revolutions'' (1962; second edition 1970; third edition 1996; fourth edition 2012) is a book about the history of science by philosopher Thomas S. Kuhn. Its publication was a landmark event in the history, philoso ...
'' (1962) that he places an emphasis on anomalous experiences similar to that which Popper places on falsification. However, he adds that anomalous experiences cannot be identified with falsification, and questions whether theories could be falsified in the manner suggested by Popper. Kuhn argues in ''The Essential Tension'' (1977) that while Popper was correct that
psychoanalysis PsychoanalysisFrom Greek: + . is a set of theories and therapeutic techniques"What is psychoanalysis? Of course, one is supposed to answer that it is many things — a theory, a research method, a therapy, a body of knowledge. In what might ...
cannot be considered a science, there are better reasons for drawing that conclusion than those Popper provided. Popper's student Imre Lakatos attempted to reconcile Kuhn's work with falsificationism by arguing that science progresses by the falsification of ''research programs'' rather than the more specific universal statements of naive falsificationism. Popper claimed to have recognised already in the 1934 version of his ''Logic of Discovery'' a fact later stressed by Kuhn, "that scientists necessarily develop their ideas within a definite theoretical framework", and to that extent to have anticipated Kuhn's central point about "normal science". However, Popper criticised what he saw as Kuhn's relativism. Also, in his collection ''Conjectures and Refutations: The Growth of Scientific Knowledge'' (Harper & Row, 1963), Popper writes, Another objection is that it is not always possible to demonstrate falsehood definitively, especially if one is using
statistical Statistics (from German: '' Statistik'', "description of a state, a country") is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a scientific, industr ...
criteria to evaluate a
null hypothesis In scientific research, the null hypothesis (often denoted ''H''0) is the claim that no difference or relationship exists between two sets of data or variables being analyzed. The null hypothesis is that any experimentally observed difference is ...
. 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, Karl, (1934) ''Logik der Forschung'', Springer. Vienna. Amplified English edition, Popper (1959), In ''Science Versus Crime'', Houck writes that 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 "Peter" Hempel (January 8, 1905 – November 9, 1997) was a German writer, philosopher, logician, and epistemologist. He was a major figure in logical empiricism, a 20th-century movement in the philosophy of science. He is e ...
. 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 is the scientific theory that matter is composed of particles called atoms. Atomic theory traces its origins to an ancient philosophical tradition known as atomism. According to this idea, if one were to take a lump of matter ...
implies that all metals melt at some temperature. An early adversary of Popper's critical rationalism, Karl-Otto Apel 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. The philosopher
Adolf Grünbaum Adolf Grünbaum (; May 15, 1923 – November 15, 2018) was a German-American philosopher of science and a critic of psychoanalysis, as well as Karl Popper's philosophy of science. He was the first Andrew Mellon Professor of Philosophy at the Unive ...
argues in '' The Foundations of Psychoanalysis'' (1984) that Popper's view that psychoanalytic theories, even in principle, cannot be falsified is incorrect. The philosopher
Roger Scruton Sir Roger Vernon Scruton (; 27 February 194412 January 2020) was an English philosopher and writer who specialised in aesthetics and political philosophy, particularly in the furtherance of traditionalist conservative views. Editor from 1982 ...
argues in '' Sexual Desire'' (1986) that Popper was mistaken to claim that Freudian theory implies no testable observation and therefore does not have genuine predictive power. Scruton maintains that Freudian theory has both "theoretical terms" and "empirical content". He points to the example of Freud's theory of repression, which in his view has "strong empirical content" and implies testable consequences. Nevertheless, Scruton also concluded that Freudian theory is not genuinely scientific. The philosopher Charles Taylor accuses Popper of exploiting his worldwide fame as an epistemologist to diminish the importance of philosophers of the 20th-century
continental tradition Continental philosophy is a term used to describe some philosophers and philosophical traditions that do not fall under the umbrella of analytic philosophy. However, there is no academic consensus on the definition of continental philosophy. Prio ...
. 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". The philosopher John Gray argues that Popper's account of scientific method would have prevented the theories of
Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
and
Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theor ...
from being accepted. The philosopher and psychologist Michel ter Hark writes in ''Popper, Otto Selz and the Rise of Evolutionary Epistemology'' (2004) that Popper took some of his ideas from his tutor, the German psychologist
Otto Selz Otto is a masculine German given name and a surname. It originates as an Old High German short form (variants ''Audo'', ''Odo'', ''Udo'') of Germanic names beginning in ''aud-'', an element meaning "wealth, prosperity". The name is recorded fro ...
. Selz never published his ideas, partly because of the rise of
Nazism Nazism ( ; german: Nazismus), the common name in English for National Socialism (german: Nationalsozialismus, ), is the far-right totalitarian political ideology and practices associated with Adolf Hitler and the Nazi Party (NSDAP) i ...
, which forced him to quit his work in 1933 and prohibited any reference to his ideas. Popper, the historian of ideas and his scholarship, is criticised in some academic quarters for his rejection of Plato and Hegel.Levinson, Ronald B. (1970). ''In Defense of Plato''. New York: Russell and Russell. p. 20. "In spite of the high rating one must accord his initial intention of fairness, his hatred for the enemies of the 'open society,' his zeal to destroy whatever seems to him destructive of the welfare of mankind, has led him into the extensive use of what may be called terminological counterpropaganda. ... With a few exceptions in Popper's favor, however, it is noticeable that reviewers possessed of special competence in particular fields—and here Lindsay is again to be included—have objected to Popper's conclusions in those very fields. ... "Social scientists and social philosophers have deplored his radical denial of historical causation, together with his espousal of Hayek's systematic distrust of larger programs of social reform; historical students of philosophy have protested his violent polemical handling of Plato, Aristotle, and particularly Hegel; ethicists have found contradictions in the ethical theory ('critical dualism') upon which his polemic is largely based."


Published works

* ''The Two Fundamental Problems of the Theory of Knowledge'', 1930–1933 (as a typescript circulating as ''Die beiden Grundprobleme der Erkenntnistheorie''; as a German book 1979, as English translation 2008), * ''
The Logic of Scientific Discovery ''The Logic of Scientific Discovery'' is a 1959 book about the philosophy of science by the philosopher Karl Popper. Popper rewrote his book in English from the 1934 (imprint '1935') German original, titled ''Logik der Forschung. Zur Erkenntnisthe ...
'', 1934 (as ''Logik der Forschung'', English translation 1959), * ''
The Poverty of Historicism ''The Poverty of Historicism'' is a 1944 book by the philosopher Karl Popper (revised in 1957), in which the author argues that the idea of historicism is dangerous and bankrupt. Publication ''The Poverty of Historicism'' was first written as a ...
'', 1936 (private reading at a meeting in Brussels, 1944–45 as a series of journal articles in ''Econometrica'', 1957 a book), * ''
The Open Society and Its Enemies ''The Open Society and Its Enemies'' is a work on political philosophy by the philosopher Karl Popper, in which the author presents a "defence of the open society against its enemies", and offers a critique of theories of teleological historicism ...
'', 1945 Vol 1 , Vol 2 * ''Quantum Theory and the Schism in Physics'', 1956–57 (as privately circulated galley proofs; published as a book 1982), * ''The Open Universe: An Argument for Indeterminism'', 1956–57 (as privately circulated galley proofs; published as a book 1982), * ''Realism and the Aim of Science'', 1956–57 (as privately circulated galley proofs; published as a book 1983), * ''Conjectures and Refutations: The Growth of Scientific Knowledge'', 1963, * ''Of Clouds and Clocks: An Approach to the Problem of Rationality and the Freedom of Man'', 1965 * ''Objective Knowledge: An Evolutionary Approach'', 1972, Rev. ed., 1979, * '' Unended Quest: An Intellectual Autobiography'', 2002 976 ) * ''The Self and Its Brain: An Argument for Interactionism'' (with Sir John C. Eccles), 1977, * ''In Search of a Better World'', 1984, * ''Die Zukunft ist offen'' (''The Future is Open'') (with
Konrad Lorenz Konrad Zacharias Lorenz (; 7 November 1903 – 27 February 1989) was an Austrian zoologist, ethologist, and ornithologist. He shared the 1973 Nobel Prize in Physiology or Medicine with Nikolaas Tinbergen and Karl von Frisch. He is often regarde ...
), 1985 (in German), * ''A World of Propensities'', 1990, * ''The Lesson of this Century'', (Interviewer: Giancarlo Bosetti, English translation: Patrick Camiller), 1992, * ''All Life is Problem Solving'', 1994, * '' The Myth of the Framework: In Defence of Science and Rationality'' (edited by Mark Amadeus Notturno) 1994. * ''Knowledge and the Mind-Body Problem: In Defence of Interaction'' (edited by Mark Amadeus Notturno) 1994 * ''The World of Parmenides'', Essays on the Presocratic Enlightenment, 1998, Edited by Arne F. Petersen with the assistance of Jørgen Mejer, * ''After The Open Society'', 2008. (Edited by Jeremy Shearmur and Piers Norris Turner, this volume contains a large number of Popper's previously unpublished or uncollected writings on political and social themes.) * ''Frühe Schriften'', 2006 (Edited by Troels Eggers Hansen, includes Popper's writings and publications from before the ''Logic'', including his previously unpublished thesis, dissertation and journal articles published that relate to the Wiener Schulreform.)


Filmography

* ''Interview Karl Popper'', Open Universiteit, 1988.


See also

*
Calculus of predispositions Calculus of predispositions is a basic part of predispositioning theory and belongs to the indeterministic procedures. Overview "The key component of any indeterministic procedure is the evaluation of a position. Since it is impossible to devise ...
*
Contributions to liberal theory Contribution or Contribute may refer to: * ''Contribution'' (album), by Mica Paris (1990) ** "Contribution" (song), title song from the album *Contribution (law), an agreement between defendants in a suit to apportion liability *Contributions, a ...
*
Evolutionary epistemology Evolutionary epistemology refers to three distinct topics: (1) the biological evolution of cognitive mechanisms in animals and humans, (2) a theory that knowledge itself evolves by natural selection, and (3) the study of the historical discovery ...
* Liberalism in Austria *
List of refugees This is a list of prominent people who fled their native country, went into exile and found refuge in another country. The list follows the current legal concept of refugee only loosely. It also includes children of people who have fled. The peopl ...
* Poper Scientific Stand up * Popper's experiment *
Popper legend Positivism is an empiricist philosophical theory that holds that all genuine knowledge is either true by definition or positive—meaning ''a posteriori'' facts derived by reason and logic from sensory experience.John J. Macionis, Linda M. Ger ...
*
Positivism dispute The positivism dispute (german: Positivismusstreit, links=no) was a political-philosophical dispute between the critical rationalists (Karl Popper, Hans Albert) and the Frankfurt School (Theodor Adorno, Jürgen Habermas) in 1961, about the method ...
* Predispositioning theory * Karl Popper - Wikiquote


Notes


References

* * * * * * * * * * * * * * * * * * * * *


Further reading

* 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
* Gattei, Stefano. ''Karl Popper's Philosophy of Science''. 2009. * Miller, David. ''Critical Rationalism: A Restatement and Defence''. 1994. * David Miller (ed.). ''Popper Selections''. * Watkins, John W. N. ''Science and Scepticism.'
Preface

Contents.
Princeton 1984 (Princeton University Press). * Jarvie, Ian Charles, Karl Milford, David W. Miller, ed. (2006). ''Karl Popper: A Centenary Assessment''. Aldershot, Hants, England; Burlington, VT: Ashgate. ::Volume I: ''Life and Times, and Values in a World of Facts''
Description

Contents.
::Volume II: ''Metaphysics and Epistemology'


Contents.
::Volume III: ''Science''


Contents.
* 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 * Cornforth, Maurice. (1968): ''The Open Philosophy and the Open Society: A Reply to Dr Karl Popper's Refutations of Marxism''. London: Lawrence & Wishart; New York: International Publishers.. * Edmonds, D., Eidinow, J. ''
Wittgenstein's Poker ''Wittgenstein's Poker: The Story of a Ten-Minute Argument Between Two Great Philosophers'' is a 2001 book by BBC journalists David Edmonds and John Eidinow about events in the history of philosophy involving Sir Karl Popper and Ludwig Wittge ...
''. New York: Ecco 2001. A review of the origin of the conflict between Popper and
Ludwig Wittgenstein Ludwig Josef Johann Wittgenstein ( ; ; 26 April 1889 – 29 April 1951) was an Austrian- British philosopher who worked primarily in logic, the philosophy of mathematics, the philosophy of mind, and the philosophy of language. He is consi ...
, 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 * Jones, Daniel Stedman. ''Masters of the Universe: Hayek, Friedman, and the Birth of Neoliberal Politics'' (2012) pp. 32–48
excerpt
* Kadvany, John ''Imre Lakatos and the Guises of Reason''. Durham and London: Duke University Press, 2001. . 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). * Levinson, Paul, 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. With forewords by
Isaac Asimov yi, יצחק אזימאװ , birth_date = , birth_place = Petrovichi, Russian SFSR , spouse = , relatives = , children = 2 , death_date = , death_place = Manhattan, New York City, U.S. , nationality = Russian (1920–1922)Soviet (192 ...
and
Helmut Schmidt Helmut Heinrich Waldemar Schmidt (; 23 December 1918 – 10 November 2015) was a German politician and member of the Social Democratic Party of Germany (SPD), who served as the chancellor of West Germany from 1974 to 1982. Before becoming Ch ...
. Includes an interview with Sir
Ernst Gombrich Sir Ernst Hans Josef Gombrich (; ; 30 March 1909 – 3 November 2001) was an Austrian-born art historian who, after settling in England in 1936, became a naturalised British citizen in 1947 and spent most of his working life in the United Ki ...
. * * 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. * Maxwell, Nicholas,
Karl Popper, Science and Enlightenment
', London, UCL Press, 2017. An exposition and development of Popper's philosophy of science and social philosophy, available free online. * Munz, Peter. ''Beyond Wittgenstein's Poker: New Light on Popper and Wittgenstein'' Aldershot, Hampshire, UK: Ashgate, 2004. . 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. ''Lexikon des Kritischen Rationalismus'', (Encyclopaedia of Critical Raionalism), Tübingen (Mohr Siebeck) 2004, . 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, . * 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. * Parusniková, Zuzana & Robert S. Cohen (2009). ''Rethinking Popper''
Description
an
contents.
Springer. * Radnitzky, Gerard, Bartley, W. W. III eds. ''Evolutionary Epistemology, Rationality, and the Sociology of Knowledge''. LaSalle, IL: Open Court Press 1987. . 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. . * 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., ed. ''The Philosophy of Karl Popper''.
Description
an

Chicago, IL: Open Court Press, 1974. One of the better contributions to the
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 has since been edited by Lewis Edwin Hahn (1981–2001), Randall Auxier (2001–2013 ...
series. Contains Popper's intellectual autobiography (v. I, pp. 2–184, also as a 1976 book), a comprehensive range of critical essays, and Popper's responses to them. (vol.I). (Vol II) * Schroeder-Heister, P. "Popper, Karl Raimund (1902–94)," '' International Encyclopedia of the Social & Behavioral Sciences'', 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., '' Popper and After: 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 The ''Stanford Encyclopedia of Philosophy'' (''SEP'') combines an online encyclopedia of philosophy with peer-reviewed publication of original papers in philosophy, freely accessible to Internet users. It is maintained by Stanford University. E ...
,'' 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". * Zippelius, Reinhold, ''Die experimentierende Methode im Recht'', Akademie der Wissenschaften Mainz. Stuttgart: Franz Steiner, 1991,


External links

* *
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* Popper, K. R.

', 1977.
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Synopsis and background of ''The poverty of historicism''


by Martin Gardner
"A Sceptical Look at 'A Skeptical Look at Karl Popper'"
by J C Lester. *
The Liberalism of Karl Popper
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John N. Gray John Nicholas Gray (born 17 April 1948) is an English political philosopher and author with interests in analytic philosophy, the history of ideas, and philosophical pessimism. He retired in 2008 as School Professor of European Thought at the ...

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''History of Twentieth-Century Philosophy of Science'', BOOK V: Karl Popper
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A science and technology hypotheses database following Karl Popper's refutability principle

Popper
BBC Radio 4 discussion with John Worrall, Anthony O'Hear & Nancy Cartwright (''In Our Time'', 8 February 2007) {{DEFAULTSORT:Popper, Karl Raimund 1902 births 1994 deaths 20th-century Austrian philosophers 20th-century British philosophers 20th-century essayists Academics of the London School of Economics Aristotelian philosophers Austrian agnostics Austrian essayists Austrian logicians Jewish emigrants from Austria to the United Kingdom after the Anschluss Austrian political philosophers Austrian social liberals British agnostics British cultural critics British ethicists British logicians British male essayists British male non-fiction writers British people of Austrian-Jewish descent British political philosophers British social commentators British social liberals Cambridge University Moral Sciences Club British consciousness researchers and theorists Critical rationalists Critics of dialectical materialism Critics of Marxism Critics of religions Epistemologists Fellows of Darwin College, Cambridge Fellows of the British Academy Fellows of the Royal Society (Statute 12) Foreign associates of the National Academy of Sciences Grand Crosses with Star and Sash of the Order of Merit of the Federal Republic of Germany Historians of philosophy Jewish agnostics Jewish ethicists Jewish philosophers Knights Bachelor Kyoto laureates in Arts and Philosophy Logicians Members of the Order of the Companions of Honour Metaphysicians Metaphysics writers Moral philosophers Naturalised citizens of the United Kingdom Ontologists Philosophers of culture Philosophers of economics Philosophers of education Philosophers of ethics and morality Philosophers of history Philosophers of logic Philosophers of mathematics Philosophers of mind Philosophers of religion Philosophers of science Philosophers of technology Political philosophers Presidents of the Aristotelian Society Rationalists Rationality theorists Recipients of the Austrian Decoration for Science and Art Recipients of the Grand Decoration for Services to the Republic of Austria Recipients of the Pour le Mérite (civil class) Social critics Social philosophers Theorists on Western civilization University of Canterbury faculty University of Vienna alumni Writers about activism and social change Writers about globalization Writers about religion and science Writers from Vienna Member of the Mont Pelerin Society