TheInfoList

The Vienna Circle (german: Wiener Kreis) of
Logical Empiricism Logical positivism, later called logical empiricism, and both of which together are also known as neopositivism, was a movement in Western philosophy Western philosophy refers to the philosophy, philosophical thought and work of the Western worl ...
was a group of
philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about Metaphysics, existence, reason, Epistemology, knowledge, Ethics, values, Philosophy of mind, mi ...

s and
scientist A scientist is a person who conducts scientific research The scientific method is an Empirical evidence, empirical method of acquiring knowledge that has characterized the development of science since at least the 17th century. It involves ...

s drawn from the
natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and ...

and
social sciences Social science is the branch The branches and leaves of a tree. A branch ( or , ) or tree branch (sometimes referred to in botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biol ...

,
logic Logic is an interdisciplinary field which studies truth and reasoning. Informal logic seeks to characterize Validity (logic), valid arguments informally, for instance by listing varieties of fallacies. Formal logic represents statements and ar ...

and
mathematics Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces in which they are contained (geometry), and quantities and their changes (cal ...
who met regularly from 1924 to 1936 at the
University of Vienna The University of Vienna (german: Universität Wien) is a public university, public research university located in Vienna, Austria. It was founded by Rudolf IV, Duke of Austria, Duke Rudolph IV in 1365 and is the oldest university in the Geograph ...
, chaired by
Moritz Schlick Friedrich Albert Moritz Schlick (; ; 14 April 1882 – 22 June 1936) was a Germany, German philosopher, physicist, and the founding father of logical positivism and the Vienna Circle. Early life and works Schlick was born in Berlin to a wealthy f ...
. The Vienna Circle's influence on
20th-century philosophy 20th-century philosophy saw the development of a number of new philosophical schools—including logical positivism Logical positivism, later called logical empiricism, and both of which together are also known as neopositivism, was a movement in ...
, especially
philosophy of science Philosophy of science is a branch of philosophy concerned with the foundations, methodology, methods, and implications of science. The central questions of this study concern Demarcation problem, what qualifies as science, the reliability of s ...
and
analytic philosophy Analytic philosophy is a branch and tradition of philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about existence Existence is the ability of an entity to interact with physical reality ...
, is immense up to the present day. Among the members of the inner circle were
Moritz Schlick Friedrich Albert Moritz Schlick (; ; 14 April 1882 – 22 June 1936) was a Germany, German philosopher, physicist, and the founding father of logical positivism and the Vienna Circle. Early life and works Schlick was born in Berlin to a wealthy f ...
, Hans Hahn,
Philipp FrankPhilipp Frank (March 20, 1884, Vienna en, Viennese , iso_code = AT-9 , registration_plate = Vehicle registration plates of Austria, W , postal_code_type = Postal code , postal_code ...
,
Otto Neurath Otto Karl Wilhelm Neurath (; 10 December 1882 – 22 December 1945) was an Austria Austria (, ; german: Österreich ), officially the Republic of Austria (german: Republik Österreich, links=no, ), is a landlocked Eastern Alps, East Alp ...

, Olga Hahn-Neurath,
Rudolf Carnap Rudolf Carnap (; ; 18 May 1891 – 14 September 1970) was a German-language philosopher who was active in Europe before 1935 and in the United States thereafter. He was a major member of the Vienna Circle The Vienna Circle (german: Wiener Krei ...
, Herbert Feigl,
Richard von Mises Richard Edler von Mises (; 19 April 1883 – 14 July 1953) was an Austrian Austrian may refer to: * Austrians, someone from Austria or of Austrian descent ** Someone who is considered an Austrian citizen, see Austrian nationality law * Something ...
,
Karl Menger Karl Menger (January 13, 1902 – October 5, 1985) was an Austrian-American mathematician. He was the son of the economist Carl Menger. He is credited with Menger's theorem. He worked on mathematics of algebras, algebra of geometries, curve and ...
,
Kurt Gödel Kurt Friedrich Gödel ( , ; April 28, 1906 – January 14, 1978) was a logician Logic is an interdisciplinary field which studies truth Truth is the property of being in accord with fact or reality.Merriam-Webster's Online Dict ...
,
Friedrich WaismannFriedrich may refer to: Names *Friedrich (surname)Friedrich or Friedrichs is a surname. Notable people with the surname include: Friedrich * Johannes Friedrich, Bishop of the Evangelical Lutheran Church in Bavaria * Ariane Friedrich, German high ...
, Felix Kaufmann, Viktor Kraft and Edgar Zilsel. In addition, the Vienna Circle was occasionally visited by
Alfred Tarski Alfred Tarski (; January 14, 1901 – October 26, 1983), born Alfred Teitelbaum,School of Mathematics and Statistics, University of St Andrews ''School of Mathematics and Statistics, University of St Andrews''. was a Polish-American logician ...
,
Hans Reichenbach Hans Reichenbach (September 26, 1891 – April 9, 1953) was a leading philosopher of science, educator, and proponent of logical empiricism. He was influential in the areas of science, education, and of logical empiricism. He founded the ''Gesell ...
,
Carl Gustav Hempel Carl Gustav "Peter" Hempel (January 8, 1905 – November 9, 1997) was a German writer A writer is a person who uses written words in different styles and techniques to communicate ideas. Writers produce different forms of literary art a ...
,
Willard Van Orman Quine Willard Van Orman Quine (; known to his friends as "Van"; June 25, 1908 – December 25, 2000) was an American philosopher and logician Logic (from Greek: grc, λογική, label=none, lit=possessed of reason Reason is the capacity of ...
,
Ernest Nagel Ernest Nagel (November 16, 1901 – September 20, 1985) was an American philosopher of science. Along with Rudolf Carnap, Hans Reichenbach, and Carl Hempel, he is sometimes seen as one of the major figures of the logical positivism, logical posi ...
,
Alfred Jules Ayer Sir Alfred Jules "Freddie" Ayer (; 29 October 1910 – 27 June 1989), usually cited as A. J. Ayer, was an English philosopher known for his promotion of logical positivism, particularly in his books ''Language, Truth, and Logic'' (1936) and ...

,
Oskar Morgenstern Oskar Morgenstern (January 24, 1902 – July 26, 1977) was a German-American German Americans (german: Deutschamerikaner, ) are Americans Americans are the Citizenship of the United States, citizens and United States nationality law, nation ...
and Frank P. Ramsey.
Ludwig Wittgenstein Ludwig Josef Johann Wittgenstein ( ; ; 26 April 1889 – 29 April 1951) was an Austrian Austrian may refer to: * Austrians, someone from Austria or of Austrian descent ** Someone who is considered an Austrian citizen, see Austrian nationali ...

and
Karl Popper Sir Karl Raimund Popper (28 July 1902 – 17 September 1994) was an Austrian-British philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of general and fundamental questions, such as tho ...

were in close contact with the Vienna Circle, but never participated in the meetings of the Schlick Circle. The philosophical position of the Vienna Circle was called
logical empiricism Logical positivism, later called logical empiricism, and both of which together are also known as neopositivism, was a movement in Western philosophy Western philosophy refers to the philosophy, philosophical thought and work of the Western worl ...
(German: ''logischer Empirismus''),
logical positivism Logical positivism, later called logical empiricism, and both of which together are also known as neopositivism, was a movement in Western philosophy Western philosophy encompasses the philosophical Philosophy (from , ) is the study of ...
or
neopositivism Logical positivism, later called logical empiricism, and both of which together are also known as neopositivism, was a movement in Western philosophy Western philosophy refers to the philosophy, philosophical thought and work of the Western worl ...
. It was influenced by
Ernst Mach Ernst Waldfried Josef Wenzel Mach (; ; 18 February 1838 – 19 February 1916) was an Austrian physicist and philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , t ...

,
David Hilbert David Hilbert (; ; 23 January 1862 – 14 February 1943) was a German mathematician This is a List of German mathematician A mathematician is someone who uses an extensive knowledge of mathematics Mathematics (from Ancient Greek, G ...
, French
conventionalism Conventionalism is the philosophical attitude that fundamental principles of a certain kind are grounded on (explicit or implicit) agreements in society, rather than on external reality. Unspoken rules play a key role in the philosophy's structur ...
(
Henri Poincaré Jules Henri Poincaré ( S: stress final syllable ; 29 April 1854 – 17 July 1912) was a French mathematician A mathematician is someone who uses an extensive knowledge of mathematics Mathematics (from Greek: ) includes the s ...
and
Pierre Duhem Pierre Maurice Marie Duhem (; 9 June 1861 – 14 September 1916) was a French theoretical physicist A physicist is a scientist A scientist is a person who conducts scientific research The scientific method is an Empirical evidence, ...

),
Gottlob Frege Friedrich Ludwig Gottlob Frege (; ; 8 November 1848 – 26 July 1925) was a German philosopher, logician, and mathematician. He worked as a mathematics professor at the University of Jena, and is understood by many to be the father of analy ...
,
Bertrand Russell Bertrand Arthur William Russell, 3rd Earl Russell (18 May 1872 – 2 February 1970) was a British polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose know ...
,
Ludwig Wittgenstein Ludwig Josef Johann Wittgenstein ( ; ; 26 April 1889 – 29 April 1951) was an Austrian Austrian may refer to: * Austrians, someone from Austria or of Austrian descent ** Someone who is considered an Austrian citizen, see Austrian nationali ...

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 physicists of all time. Einstein is known for developing the theory of relativity The theo ...

. The Vienna Circle was pluralistic and committed to the ideals of the
Enlightenment Enlightenment, enlighten or enlightened may refer to: Age of Enlightenment * Age of Enlightenment, period in Western intellectual history from the late 17th to late 18th century, centered in France but also encompassing: ** Midlands Enlightenment ...
. It was unified by the aim of making philosophy scientific with the help of modern
logic Logic is an interdisciplinary field which studies truth and reasoning. Informal logic seeks to characterize Validity (logic), valid arguments informally, for instance by listing varieties of fallacies. Formal logic represents statements and ar ...

. Main topics were foundational debates in the natural and social sciences, logic and mathematics; the modernization of
empiricism In philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about Metaphysics, existence, reason, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, l ...
by modern logic; the search for an empiricist criterion of meaning; the critique of
metaphysics Metaphysics is the branch of philosophy that studies the first principles of being, identity and change, space and time, causality, necessity and possibility. It includes questions about the nature of consciousness and the relationship between ...

and the unification of the sciences in the
unity of science The unity of science is a thesis in philosophy of science Philosophy of science is a branch of philosophy concerned with the foundations, methodology, methods, and implications of science. The central questions of this study concern Demarcatio ...
. The Vienna Circle appeared in public with the publication of various book series – ''Schriften zur wissenschaftlichen Weltauffassung'' (''Monographs on the Scientific World-Conception''), ''Einheitswissenschaft'' (''Unified Science'') and the journal ''
Erkenntnis ''Erkenntnis'' is a journal of philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and P ...
'' – and the organization of international conferences in
Prague Prague ( ; cs, Praha ; german: Prag, ; la, Praga) is the capital and largest city A city is a large human settlement In geography, statistics and archaeology, a settlement, locality or populated place is a community in which people ...

;
Königsberg Königsberg (, , ) was the name for the historic Prussian city that is now Kaliningrad, Russia. Königsberg was founded in 1255 on the site of the ancient Old Prussian settlement ''Twangste'' by the Teutonic Knights during the Northern Crusade ...

(today known as
Kaliningrad Kaliningrad ( ; rus, Калининград, p=kəlʲɪnʲɪnˈɡrat, links=y), until 1946 known as Königsberg (, ), is the largest city and the administrative centreAn administrative centre is a seat of regional administration or local gover ...

);
Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, most populous city of France, with an estimated population of 2,175,601 residents , in an area of more than . Since the 17th century, Paris ha ...

;
Copenhagen Copenhagen ( da, København ) is the capital and most populous city of Denmark. As of 1 January 2021, the city had a population of 799,033 (638,117 in Copenhagen Municipality, 103,677 in Frederiksberg Municipality, 42,670 in Tårnby Municipal ...

;
Cambridge Cambridge ( ) is a university city and the county town In the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' ...

, UK, and
Cambridge, Massachusetts Cambridge ( ) is a city in Middlesex County, Massachusetts, Middlesex County, Massachusetts, and part of the Greater Boston, Boston metropolitan area as a major suburb of Boston. , it was the fifth most populous city in the state, behind Boston, ...
. Its public profile was provided by the ''Ernst Mach Society'' (German: ''Verein Ernst Mach'') through which members of the Vienna Circle sought to popularize their ideas in the context of programmes for popular education in Vienna. During the era of
Austrofascism The Fatherland Front ( de-AT, Vaterländische Front, ''VF'') was the right-wing Right-wing politics embraces the view that certain social orders and Social stratification, hierarchies are inevitable, natural, normal, or desirable, typically ...
and after the annexation of Austria by
Nazi Germany Nazi Germany, (lit. "National Socialist State"), ' (lit. "Nazi State") for short; also ' (lit. "National Socialist Germany") officially known as the German Reich from 1933 until 1943, and the Greater German Reich from 1943 to 1945, was ...

most members of the Vienna Circle were forced to emigrate. The murder of Schlick in 1936 by a former student put an end to the Vienna Circle in Austria.

# History of the Vienna Circle

The history and development of the Vienna Circle shows various stages:

## The "First Vienna Circle" (1907–1912)

The pre-history of the Vienna Circle began with meetings on the
philosophy of science Philosophy of science is a branch of philosophy concerned with the foundations, methodology, methods, and implications of science. The central questions of this study concern Demarcation problem, what qualifies as science, the reliability of s ...
and
epistemology Epistemology (; ) is the Outline of philosophy, branch of philosophy concerned with knowledge. Epistemologists study the nature, origin, and scope of knowledge, epistemic Justification (epistemology), justification, the Reason, rationality o ...

from 1908 on, promoted by
Philipp FrankPhilipp Frank (March 20, 1884, Vienna en, Viennese , iso_code = AT-9 , registration_plate = Vehicle registration plates of Austria, W , postal_code_type = Postal code , postal_code ...
, Hans Hahn and
Otto Neurath Otto Karl Wilhelm Neurath (; 10 December 1882 – 22 December 1945) was an Austria Austria (, ; german: Österreich ), officially the Republic of Austria (german: Republik Österreich, links=no, ), is a landlocked Eastern Alps, East Alp ...

. Hans Hahn, the oldest of the three (1879–1934), was a mathematician. He received his degree in
mathematics Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces in which they are contained (geometry), and quantities and their changes (cal ...
in 1902. Afterwards he studied under the direction of
Ludwig Boltzmann Ludwig Eduard Boltzmann (; 20 February 1844 – 5 September 1906) was an Austria Austria, officially the Republic of Austria, is a landlocked country in the southern part of Central Europe, located on the Eastern Alps. It is compo ...
in Vienna and
David Hilbert David Hilbert (; ; 23 January 1862 – 14 February 1943) was a German mathematician This is a List of German mathematician A mathematician is someone who uses an extensive knowledge of mathematics Mathematics (from Ancient Greek, G ...
,
Felix Klein Christian Felix Klein (; 25 April 1849 – 22 June 1925) was a German mathematician and mathematics educator, known for his work with group theory, complex analysis, non-Euclidean geometry, and on the associations between geometry and group ...
and
Hermann Minkowski Hermann Minkowski (; ; 22 June 1864 – 12 January 1909) was a German mathematician A mathematician is someone who uses an extensive knowledge of mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as ...

in
Göttingen Göttingen (, , ; nds, Chöttingen) is a university city in Lower Saxony Lower Saxony (german: Niedersachsen ; nds, Neddersassen; stq, Läichsaksen) is a German state The Federal Republic of Germany, as a federal state, consist ...
. In 1905 he received the
Habilitation Habilitation is the procedure to achieve the highest university degree in many European countries in which the candidate fulfills certain criteria set by the university which require excellence in research, teaching, and further education. Its qu ...
in mathematics. He taught at
Innsbruck Innsbruck (; bar, Innschbruck, label=Austro-Bavarian Austro-Bavarian (also known as Austrian or Bavarian; or ; german: Bairisch ) is a West Germanic language spoken in parts of Bavaria and most of Austria. Before 1945, Austro-Bavarian was ...

(1905–1906) and
Vienna Vienna ( ; german: Wien ; bar, Wean, label=Bavarian language, Austro-Bavarian ) is the Capital city, national capital, largest city, and one of States of Austria, nine states of Austria. Vienna is Austria's List of cities and towns in Austria, mos ...

(from 1909).
Otto Neurath Otto Karl Wilhelm Neurath (; 10 December 1882 – 22 December 1945) was an Austria Austria (, ; german: Österreich ), officially the Republic of Austria (german: Republik Österreich, links=no, ), is a landlocked Eastern Alps, East Alp ...

(1882–1945) studied
mathematics Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces in which they are contained (geometry), and quantities and their changes (cal ...
,
political economy Political economy is the study of production Production may be: Economics and business * Production (economics) * Production, the act of manufacturing goods * Production, in the outline of industrial organization, the act of making products ( ...
, and
history History (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...

in Vienna and Berlin. From 1907 to 1914 he taught in Vienna at the Neue Wiener Handelsakademie (Viennese Commercial Academy). Neurath married Olga, Hahn's sister, in 1911.
Philipp FrankPhilipp Frank (March 20, 1884, Vienna en, Viennese , iso_code = AT-9 , registration_plate = Vehicle registration plates of Austria, W , postal_code_type = Postal code , postal_code ...
, the youngest of the group (1884–1966), studied
physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. "Physical scie ...

at Göttingen and Vienna with Ludwig Boltzmann, David Hilbert and Felix Klein. From 1912, he held the chair of
theoretical physics Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict List of natural phenomena, natural phenomena. This is in contrast to experimental ph ...
in the German University in Prague. Their meetings were held in Viennese coffeehouses from 1907 onward. Frank remembered: A number of further authors were discussed in the meetings such as Brentano, Meinong,
Helmholtz Hermann Ludwig Ferdinand von Helmholtz (31 August 1821 – 8 September 1894) was a German physicist and physician who made significant contributions in several scientific fields. The largest German association of research institutions, the Hel ...

,
Hertz The hertz (symbol: Hz) is the unit Unit may refer to: Arts and entertainment * UNIT Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' * Unit of action ...

,
Husserl , thesis1_title = Beiträge zur Variationsrechnung (Contributions to the Calculus of Variations) , thesis1_url = https://fedora.phaidra.univie.ac.at/fedora/get/o:58535/bdef:Book/view , thesis1_year = 1883 , thesis2_title ...
,
Freud Sigmund Freud ( , ; born Sigismund Schlomo Freud; 6 May 1856 – 23 September 1939) was an Austrian neurologist Neurology (from el, νεῦρον (neûron), "string, nerve" and the suffix -logia ''-logy'' is a suffix in the English l ...

Lenin Vladimir Ilyich Ulyanov. ( 1870 – 21 January 1924), better known by his alias Lenin,. was a Russian revolutionary, politician, and political theorist. He served as the first and founding Chairman of the Council of People's Commissars of th ...

and
Frege Frege is a surname. Notable people with the surname include: * Carola Frege (born 1965), German scholar *Élodie Frégé, French singer and actress *Gottlob Frege (1848 – 1925), German philosopher, logician, and mathematician. * Livia Fre ...
. Presumably the meetings stopped in 1912, when Frank went to
Prague Prague ( ; cs, Praha ; german: Prag, ; la, Praga) is the capital and largest city A city is a large human settlement In geography, statistics and archaeology, a settlement, locality or populated place is a community in which people ...

, to hold the chair of theoretical physics left vacant by
Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest physicists of all time. Einstein is known for developing the theory of relativity The theo ...

. Hahn left Vienna during
World War I World War I, often abbreviated as WWI or WW1, also known as the First World War or the Great War, was a global war A world war is "a war engaged in by all or most of the principal nations of the world". The term is usually reserved for ...

and returned in 1921.

## The formative years (1918–1924)

The formation of ''the'' Vienna Circle began with Hahn returning to Vienna in 1921. Together with the mathematician
Kurt Reidemeister Kurt Werner Friedrich Reidemeister (13 October 1893 – 8 July 1971) was a mathematician A mathematician is someone who uses an extensive knowledge of mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics ...
he organized seminars on
Ludwig Wittgenstein Ludwig Josef Johann Wittgenstein ( ; ; 26 April 1889 – 29 April 1951) was an Austrian Austrian may refer to: * Austrians, someone from Austria or of Austrian descent ** Someone who is considered an Austrian citizen, see Austrian nationali ...

's ''
Tractatus logico-philosophicus The ''Tractatus Logico-Philosophicus'' (widely abbreviated and cited as TLP) is a book-length philosophical work by the Austrian philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of genera ...
'' and on Whitehead and Russell's ''
Principia Mathematica Image:Principia Mathematica 54-43.png, 500px, ✸54.43: "From this proposition it will follow, when arithmetical addition has been defined, that 1 + 1 = 2." – Volume I, 1st editionp. 379(p. 362 in 2nd edition; p. 360 in abridged v ...
''. With the support of Hahn,
Moritz Schlick Friedrich Albert Moritz Schlick (; ; 14 April 1882 – 22 June 1936) was a Germany, German philosopher, physicist, and the founding father of logical positivism and the Vienna Circle. Early life and works Schlick was born in Berlin to a wealthy f ...
was appointed to the chair of philosophy of the inductive sciences at the University of Vienna in 1922 – the chair formerly held by
Ernst Mach Ernst Waldfried Josef Wenzel Mach (; ; 18 February 1838 – 19 February 1916) was an Austrian physicist and philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , t ...

and partly by
Boltzmann Ludwig Eduard Boltzmann (; 20 February 1844 – 5 September 1906) was an Austria Austria (, ; german: Österreich ), officially the Republic of Austria (german: Republik Österreich, links=no, ), is a landlocked Eastern Alps, East Al ...

. Schlick had already published two important works ''Raum und Zeit in die gegenwärtigen Physik'' (''Space and Time in contemporary Physics'') in 1917 and ''Allgemeine Erkenntnislehre'' (''General Theory of Knowledge'') in 1918. Immediately after Schlick's arrival in Vienna, he organized discussions with the mathematicians around Hahn. In 1924 Schlick's students
Friedrich WaismannFriedrich may refer to: Names *Friedrich (surname)Friedrich or Friedrichs is a surname. Notable people with the surname include: Friedrich * Johannes Friedrich, Bishop of the Evangelical Lutheran Church in Bavaria * Ariane Friedrich, German high ...
and Herbert Feigl suggested to their teacher a sort of regular "evening circle". From winter term 1924 on regular meetings were held at the Institute of Mathematics in Vienna's Boltzmanngasse 5 on personal invitation by Schlick. These discussions can be seen as the beginning of the Vienna Circle.

## The non-public phase of the Vienna Circle – The Schlick Circle (1924–1928)

The group that met from 1924 on was quite diverse and included not only recognized scientists such as Schlick, Hahn, Kraft, Philipp Frank, Neurath, Olga Hahn-Neurath, and
Heinrich GomperzHeinrich Gomperz (January 18, 1873 in Vienna en, Viennese , iso_code = AT-9 , registration_plate = Vehicle registration plates of Austria, W , postal_code_type = Postal code , postal_code ...
, but also younger students and doctoral candidates. In addition, the group invited foreign visitors. In 1926 Schlick and Hahn arranged to bring
Rudolf Carnap Rudolf Carnap (; ; 18 May 1891 – 14 September 1970) was a German-language philosopher who was active in Europe before 1935 and in the United States thereafter. He was a major member of the Vienna Circle The Vienna Circle (german: Wiener Krei ...
to the University of Vienna as a ''Privatdozent'' (private lecturer). Carnap's ''Logical Structure of the World'' was intensely discussed in the Circle. Also Wittgenstein's ''Tractatus logico-philosophicus'' was read out loud and discussed. From 1927 on personal meetings were arranged between Wittgenstein and Schlick, Waismann, Carnap and Feigl.

## The public phase – Schlick Circle and ''Verein Ernst Mach'' (1928–1934)

In 1928 the ''Verein Ernst Mach'' (''Ernst Mach Society'') was founded, with Schlick as its chairman. The aim of the society was the spreading of a "scientific world conception" through public lectures that were in large part held by members of the Vienna Circle. In 1929 the Vienna Circle made its first public appearance under this name – invented by Neurath – with the publication of its manifesto ''Wissenschaftliche Weltauffassung. Der Wiener Kreis'' (''The Scientific Conception of the World. The Vienna Circle'' also known as ''Viewing the World Scientifically: The Vienna Circle''Edmunds, D. and Eidenow, J. ''Wittgenstein's Poker: The Story of a Ten-Minute Argument Between Two Great Philosophers,'' 2001, page 151.) The pamphlet is dedicated to Schlick, and its preface was signed by Hahn, Neurath and Carnap. The manifesto was presented at the ''Tagung für Erkenntnislehre der exakten Wissenschaften'' (''Conference on the Epistemology of the Exact Sciences'') in autumn 1929, organized by the Vienna Circle together with the
Berlin Circle The Berlin Circle (german: die Berliner Gruppe) was a group that maintained logical empiricist Logical positivism, later called logical empiricism, and both of which together are also known as neopositivism, was a movement in Western philosophy wh ...
. This conference was the first international appearance of
logical empiricism Logical positivism, later called logical empiricism, and both of which together are also known as neopositivism, was a movement in Western philosophy Western philosophy refers to the philosophy, philosophical thought and work of the Western worl ...
and the first of a number of conferences:
Königsberg Königsberg (, , ) was the name for the historic Prussian city that is now Kaliningrad, Russia. Königsberg was founded in 1255 on the site of the ancient Old Prussian settlement ''Twangste'' by the Teutonic Knights during the Northern Crusade ...

(
1930 Events January * January 6 ** The first diesel engine automobile trip is completed (Indianapolis, Indiana, to New York City) by Clessie Cummins, founder of the company Cummins. ** An early literary character licensing agreement is signed by ...
),
Prague Prague ( ; cs, Praha ; german: Prag, ; la, Praga) is the capital and largest city A city is a large human settlement In geography, statistics and archaeology, a settlement, locality or populated place is a community in which people ...

(1934),
Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, most populous city of France, with an estimated population of 2,175,601 residents , in an area of more than . Since the 17th century, Paris ha ...

(1935), (1936),
Cambridge Cambridge ( ) is a university city and the county town In the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' ...

, UK (1938), Cambridge, Mass. (1939), and
Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive map of Chicago , coordinates = , coordinates_footnotes = , subdivision_type = Country , subdivision_name ...

(1941). While primarily known for its views on the natural sciences and metaphysics, the public phase of the Vienna Circle was explicitly political. Neurath and Schlick were both
socialists Socialism is a political Politics (from , ) is the set of activities that are associated with making decisions In psychology, decision-making (also spelled decision making and decisionmaking) is regarded as the Cognition, cognitive pr ...
and believed the rejection of magic was a necessary component for liberation of the working classes. The manifesto linked
Karl Marx Karl Heinrich Marx (; 5 May 1818 – 14 March 1883) was a German philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, M ...

and
Friedrich Nietzsche Friedrich Wilhelm Nietzsche (; or ; 15 October 1844 – 25 August 1900) was a German philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of general and fundamental questions, such as thos ...

to their political and anti-metaphysical views, indicating a blur between what are now considered two separate schools of contemporary philosophy -
analytic philosophy Analytic philosophy is a branch and tradition of philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about existence Existence is the ability of an entity to interact with physical reality ...
and
continental philosophy Continental philosophy is a set of 19th- and 20th-century philosophical Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, existence, knowledge Knowledge is a familiarity, awarenes ...
. In 1930 the Vienna Circle and the Berlin Society took over the journal ''Annalen der Philosophie'' and made it the main journal of logical empiricism under the title ''
Erkenntnis ''Erkenntnis'' is a journal of philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and P ...
'', edited by Carnap and Reichenbach. In addition, the Vienna Circle published a number of book series: ''Schriften zur wissenschaftlichen Weltauffassung'' (''Monographs on the Scientific World-Conception'', ed. by Schlick und Frank, 1928–1937), ''Einheitswissenschaft'' (''Unified Science'', edited by Neurath, 1933–1939), and later the ''
International Encyclopedia of Unified Science The ''International Encyclopedia of Unified Science'' (''IEUS'') was a series of publications devoted to unified science"Unified Science" can refer to any of three related strands in contemporary thought. * Belief in the unity of science was a cen ...
'' (edited by Neurath, Carnap and Charles W. Morris, 1938–1970).

## Disintegration, emigration, internationalization (1934–1938)

From the beginning of the 1930s first signs of disintegration appeared for political and
racist Racism is the belief that groups of humans possess different behavioral traits corresponding to inherited attributes and can be divided based on the superiority Superior may refer to: *Superior (hierarchy), something which is higher in a hi ...

reasons: Herbert Feigl left Austria in 1930. Carnap was appointed to a chair at
Prague University Charles University, known also as Charles University in Prague ( cs, Univerzita Karlova (UK); la, Universitas Carolina; german: Karls-Universität) or historically as the University of Prague ( la, Universitas Pragensis), is the oldest and larges ...
in 1931 and left for Chicago in 1935. 1934 marks an important break: Hahn died after surgery, Neurath fled to Holland because of the victory of
Austrofascism The Fatherland Front ( de-AT, Vaterländische Front, ''VF'') was the right-wing Right-wing politics embraces the view that certain social orders and Social stratification, hierarchies are inevitable, natural, normal, or desirable, typically ...
in the
Austrian Civil War The Austrian Civil War (german: Österreichischer Bürgerkrieg), also known as the February Uprising (german: Februarkämpfe), is a term sometimes used for a few days of skirmishes between Fascist and Socialist forces between 12 and 16 February 1 ...
following which the ''Ernst Mach Society'' was dissolved for political reasons by the
Schuschnigg Kurt Alois Josef Johann Schuschnigg (; 14 December 1897 – 18 November 1977) was an Austrian Fatherland Front politician who was the Chancellor Chancellor ( la, links=no, cancellarius) is a title of various official positions in the governmen ...
regime. The murder of Moritz Schlick by the former student Hans Nelböck for political and personal reasons in 1936 set an end to the meetings of the Schlick Circle. Some members of the circle such as Kraft, Waismann, Zilsel, Menger and Gomperz continued to meet occasionally. But the annexation of Austria to
Nazi Germany Nazi Germany, (lit. "National Socialist State"), ' (lit. "Nazi State") for short; also ' (lit. "National Socialist Germany") officially known as the German Reich from 1933 until 1943, and the Greater German Reich from 1943 to 1945, was ...

in 1938 meant the definite end of the activities of the Vienna Circle in Austria. With the emigration went along the internationalization of
logical empiricism Logical positivism, later called logical empiricism, and both of which together are also known as neopositivism, was a movement in Western philosophy Western philosophy refers to the philosophy, philosophical thought and work of the Western worl ...
. Many former members of the Vienna Circle and the
Berlin Circle The Berlin Circle (german: die Berliner Gruppe) was a group that maintained logical empiricist Logical positivism, later called logical empiricism, and both of which together are also known as neopositivism, was a movement in Western philosophy wh ...
emigrated to the
English-speaking world Speakers of English English usually refers to: * English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which has eventually become the Wo ...
where they had an immense influence on the development of
philosophy of science Philosophy of science is a branch of philosophy concerned with the foundations, methodology, methods, and implications of science. The central questions of this study concern Demarcation problem, what qualifies as science, the reliability of s ...
. The
unity of science The unity of science is a thesis in philosophy of science Philosophy of science is a branch of philosophy concerned with the foundations, methodology, methods, and implications of science. The central questions of this study concern Demarcatio ...
movement for the construction of an ''International Encyclopedia of Unified Science'', promoted mainly by Neurath, Carnap, and Morris, is symptomatic of the internationalization of logical empiricism, organizing numerous international conferences and the publication of the ''International Encyclopedia of Unified Science''.

## Overview of the members of the Vienna Circle

Apart from the central figures of the Schlick Circle the question of membership in the Vienna Circle is in many cases unsettled. The partition into "members" and "those sympathetic to the Vienna Circle" produced in the manifesto from 1929 is representative only of a specific moment in the development of the Circle. Depending on the criteria used (regular attendance, philosophical affinities etc.) there are different possible distributions in "inner circle" and "periphery". In the following list (in alphabetical order), the "inner circle" is defined using the criterion of regular attendance. The "periphery" comprises occasional visitors, foreign visitors and leading intellectual figures who stood in regular contact with the Circle (such as Wittgenstein and Popper). Inner Circle:
Gustav Bergmann Gustav Bergmann (May 4, 1906 – April 21, 1987) was an Austrian-born American philosopher. He studied at the University of Vienna The University of Vienna (german: link=no, Universität Wien) is a public university A public university or ...
,
Rudolf Carnap Rudolf Carnap (; ; 18 May 1891 – 14 September 1970) was a German-language philosopher who was active in Europe before 1935 and in the United States thereafter. He was a major member of the Vienna Circle The Vienna Circle (german: Wiener Krei ...
, Herbert Feigl,
Philipp FrankPhilipp Frank (March 20, 1884, Vienna en, Viennese , iso_code = AT-9 , registration_plate = Vehicle registration plates of Austria, W , postal_code_type = Postal code , postal_code ...
,
Kurt Gödel Kurt Friedrich Gödel ( , ; April 28, 1906 – January 14, 1978) was a logician Logic is an interdisciplinary field which studies truth Truth is the property of being in accord with fact or reality.Merriam-Webster's Online Dict ...
, Hans Hahn, Olga Hahn-Neurath, Béla Juhos, Felix Kaufmann, Victor Kraft,
Karl Menger Karl Menger (January 13, 1902 – October 5, 1985) was an Austrian-American mathematician. He was the son of the economist Carl Menger. He is credited with Menger's theorem. He worked on mathematics of algebras, algebra of geometries, curve and ...
,
Richard von Mises Richard Edler von Mises (; 19 April 1883 – 14 July 1953) was an Austrian Austrian may refer to: * Austrians, someone from Austria or of Austrian descent ** Someone who is considered an Austrian citizen, see Austrian nationality law * Something ...
,
Otto Neurath Otto Karl Wilhelm Neurath (; 10 December 1882 – 22 December 1945) was an Austria Austria (, ; german: Österreich ), officially the Republic of Austria (german: Republik Österreich, links=no, ), is a landlocked Eastern Alps, East Alp ...

, Rose Rand, Josef Schächter,
Moritz Schlick Friedrich Albert Moritz Schlick (; ; 14 April 1882 – 22 June 1936) was a Germany, German philosopher, physicist, and the founding father of logical positivism and the Vienna Circle. Early life and works Schlick was born in Berlin to a wealthy f ...
,
Friedrich WaismannFriedrich may refer to: Names *Friedrich (surname)Friedrich or Friedrichs is a surname. Notable people with the surname include: Friedrich * Johannes Friedrich, Bishop of the Evangelical Lutheran Church in Bavaria * Ariane Friedrich, German high ...
, Edgar Zilsel. Periphery:
Alfred Jules Ayer Sir Alfred Jules "Freddie" Ayer (; 29 October 1910 – 27 June 1989), usually cited as A. J. Ayer, was an English philosopher known for his promotion of logical positivism, particularly in his books ''Language, Truth, and Logic'' (1936) and ...

, Egon Brunswik, Karl Bühler, Josef Frank (architect), Josef Frank, Else Frenkel-Brunswik,
Heinrich GomperzHeinrich Gomperz (January 18, 1873 in Vienna en, Viennese , iso_code = AT-9 , registration_plate = Vehicle registration plates of Austria, W , postal_code_type = Postal code , postal_code ...
,
Carl Gustav Hempel Carl Gustav "Peter" Hempel (January 8, 1905 – November 9, 1997) was a German writer A writer is a person who uses written words in different styles and techniques to communicate ideas. Writers produce different forms of literary art a ...
, Eino Kaila, Hans Kelsen, Charles W. Morris, Arne Næss, Arne Naess, Karl Raimund Popper,
Willard Van Orman Quine Willard Van Orman Quine (; known to his friends as "Van"; June 25, 1908 – December 25, 2000) was an American philosopher and logician Logic (from Greek: grc, λογική, label=none, lit=possessed of reason Reason is the capacity of ...
, Frank P. Ramsey,
Hans Reichenbach Hans Reichenbach (September 26, 1891 – April 9, 1953) was a leading philosopher of science, educator, and proponent of logical empiricism. He was influential in the areas of science, education, and of logical empiricism. He founded the ''Gesell ...
,
Kurt Reidemeister Kurt Werner Friedrich Reidemeister (13 October 1893 – 8 July 1971) was a mathematician A mathematician is someone who uses an extensive knowledge of mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics ...
,
Alfred Tarski Alfred Tarski (; January 14, 1901 – October 26, 1983), born Alfred Teitelbaum,School of Mathematics and Statistics, University of St Andrews ''School of Mathematics and Statistics, University of St Andrews''. was a Polish-American logician ...
, Olga Taussky-Todd,
Ludwig Wittgenstein Ludwig Josef Johann Wittgenstein ( ; ; 26 April 1889 – 29 April 1951) was an Austrian Austrian may refer to: * Austrians, someone from Austria or of Austrian descent ** Someone who is considered an Austrian citizen, see Austrian nationali ...

.

## Reception in the United States and the United Kingdom

logical positivism Logical positivism, later called logical empiricism, and both of which together are also known as neopositivism, was a movement in Western philosophy Western philosophy encompasses the philosophical Philosophy (from , ) is the study of ...
in the United States occurred throughout the 1920s and 1930s. In 1929 and in 1932, Schlick was a Visiting Professor at Stanford University, Stanford, while Feigl, who immigrated to the United States in 1930, became lecturer (1931) and professor (1933) at the University of Iowa. The definite diffusion of logical positivism in the United States was due to Carl Hempel, Hans Reichenbach, Rudolf Carnap, Philipp Frank, and Herbert Feigl, who emigrated and taught in the United States. Another link to the United States is
Willard Van Orman Quine Willard Van Orman Quine (; known to his friends as "Van"; June 25, 1908 – December 25, 2000) was an American philosopher and logician Logic (from Greek: grc, λογική, label=none, lit=possessed of reason Reason is the capacity of ...
, who traveled in 1932 and 1933 as a Sheldon Traveling Fellow to
Vienna Vienna ( ; german: Wien ; bar, Wean, label=Bavarian language, Austro-Bavarian ) is the Capital city, national capital, largest city, and one of States of Austria, nine states of Austria. Vienna is Austria's List of cities and towns in Austria, mos ...

,
Prague Prague ( ; cs, Praha ; german: Prag, ; la, Praga) is the capital and largest city A city is a large human settlement In geography, statistics and archaeology, a settlement, locality or populated place is a community in which people ...

, and Warsaw. Moreover, American semiotician and philosopher Charles W. Morris helped many German and Austrian philosophers emigrate to the United States, including Rudolf Carnap, in 1936. In the United Kingdom it was
Alfred Jules Ayer Sir Alfred Jules "Freddie" Ayer (; 29 October 1910 – 27 June 1989), usually cited as A. J. Ayer, was an English philosopher known for his promotion of logical positivism, particularly in his books ''Language, Truth, and Logic'' (1936) and ...

who acquainted the British academia with the work of the Vienna Circle with his book ''Language, Truth, and Logic'' (1936).
Karl Popper Sir Karl Raimund Popper (28 July 1902 – 17 September 1994) was an Austrian-British philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of general and fundamental questions, such as tho ...

was also important for the reception and critique of their work, even though he never participated in the meetings of the Vienna Circle.

# Congresses and publications

The Vienna Circle was very active in advertising their new philosophical ideas. Several congresses on
epistemology Epistemology (; ) is the Outline of philosophy, branch of philosophy concerned with knowledge. Epistemologists study the nature, origin, and scope of knowledge, epistemic Justification (epistemology), justification, the Reason, rationality o ...

and philosophy of science were organized, with the help of the
Berlin Circle The Berlin Circle (german: die Berliner Gruppe) was a group that maintained logical empiricist Logical positivism, later called logical empiricism, and both of which together are also known as neopositivism, was a movement in Western philosophy wh ...
. There were some preparatory congresses: Prague (1929),
Königsberg Königsberg (, , ) was the name for the historic Prussian city that is now Kaliningrad, Russia. Königsberg was founded in 1255 on the site of the ancient Old Prussian settlement ''Twangste'' by the Teutonic Knights during the Northern Crusade ...

(1930), Prague (1934) and then the first congress on scientific philosophy held in
Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, most populous city of France, with an estimated population of 2,175,601 residents , in an area of more than . Since the 17th century, Paris ha ...

(1935), followed by congresses in
Copenhagen Copenhagen ( da, København ) is the capital and most populous city of Denmark. As of 1 January 2021, the city had a population of 799,033 (638,117 in Copenhagen Municipality, 103,677 in Frederiksberg Municipality, 42,670 in Tårnby Municipal ...

(1936), Paris (1937),
Cambridge Cambridge ( ) is a university city and the county town In the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' ...

, UK (1938),
Cambridge, Massachusetts Cambridge ( ) is a city in Middlesex County, Massachusetts, Middlesex County, Massachusetts, and part of the Greater Boston, Boston metropolitan area as a major suburb of Boston. , it was the fifth most populous city in the state, behind Boston, ...
. (1939). The Second Conference on the Epistemology of the Exact Sciences, Königsberg congress (1930) was very important, for Kurt Gödel announced that he had proven the Gödel's completeness theorem, completeness of first-order logic and the Gödel's incompleteness theorem, incompleteness of formal arithmetic. Another very interesting congress was the one held in Copenhagen (1936), which was dedicated to quantum physics and causality. Between 1928 and 1937, the Vienna Circle published ten books in a collection named ''Schriften zur wissenschaftlichen Weltauffassung'' (''Monographs on the Scientific World-Conception''), edited by Schlick and Frank. Karl Raimund Popper's book ''Logik der Forschung'' was published in this collection. Seven works were published in another collection, called ''Einheitswissenschaft'' (''Unified Science''). In 1930 Rudolf Carnap and Hans Reichenbach undertook the editorship of the journal ''Erkenntnis'', which was published between 1930 and 1940 (from 1939 the editors were Otto Neurath, Rudolf Carnap and Charles Morris). The following is the list of works published in the two collections edited by the Vienna Circle. ''Schriften zur wissenschaftlichen Weltauffassung'' (''Monographs on the Scientific World-Conception''), edited by Schlick and Frank: *
Richard von Mises Richard Edler von Mises (; 19 April 1883 – 14 July 1953) was an Austrian Austrian may refer to: * Austrians, someone from Austria or of Austrian descent ** Someone who is considered an Austrian citizen, see Austrian nationality law * Something ...
, ''Wahrscheinlichkeit, Statistik und Wahrheit'', 1928 (''Probability, Statistics, and Truth'', New York: Macmillan company, 1939) * Rudolf Carnap, ''Abriss der Logistik'', 1929 * Moritz Schlick, ''Fragen der Ethik'', 1930 (''Problems of Ethics'', New York: Prentice-Hall, 1939) * Otto Neurath, ''Empirische Soziologie'', 1931 * Philipp Frank, ''Das Kausalgesetz und seine Grenzen'', 1932 (''The Law of Causality and its Limits'', Dordrecth; Boston: Kluwer, 1997) * Otto Kant, ''Zur Biologie der Ethik'', 1932 * Rudolf Carnap, ''Logische Syntax der Sprache'', 1934 (''The Logical Syntax of Language'', New York: Humanities, 1937) * Karl Raimund Popper, ''Logik der Forschung'', 1934 (''The Logic of Scientific Discovery'', New York: Basic Books, 1959) *Josef Schächter, ''Prolegomena zu einer kritischen Grammatik'', 1935 (''Prolegomena to a Critical Grammar'', Dordrecht; Boston: D. Reidel Pub. Co., 1973) * Victor Kraft, ''Die Grundlagen einer wissenschaftliche Wertlehre'', 1937 (''Foundations for a Scientific Analysis of Value'', Dordrecht; Boston: D. Reidel Pub. Co., 1981) ''Einheitswissenschaft'' (''Unified Science''), edited by Carnap, Frank, Hahn, Neurath, Jørgensen (after Hahn's death), Morris (from 1938): * Hans Hahn, ''Logik, Mathematik und Naturerkennen'', 1933 * Otto Neurath, ''Einheitswissenschaft und Psychologie'', 1933 * Rudolf Carnap, ''Die Aufgabe der Wissenschaftlogik'', 1934 * Philipp Frank, ''Das Ende der mechanistischen Physik'', 1935 * Otto Neurath, ''Was bedeutet rationale Wirtschaftsbetrachtung'', 1935 * Otto Neurath, Egon Brunswik, E. Brunswik, C. Hull, G. Mannoury, J. Woodger, ''Zur Enzyklopädie der Einheitswissenschaft''. Vorträge, 1938 * Richard von Mises, ''Ernst Mach und die empiristische Wissenschaftauffassung'', 1939 These works are translated in ''Unified Science: The Vienna Circle Monograph Series Originally Edited by Otto Neurath'', Kluwer, 1987. Monographs, arranged in chronological order, published in the ''
International Encyclopedia of Unified Science The ''International Encyclopedia of Unified Science'' (''IEUS'') was a series of publications devoted to unified science"Unified Science" can refer to any of three related strands in contemporary thought. * Belief in the unity of science was a cen ...
'': * Otto Neurath, Niels Bohr, John Dewey,
Bertrand Russell Bertrand Arthur William Russell, 3rd Earl Russell (18 May 1872 – 2 February 1970) was a British polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose know ...
, Rudolf Carnap, Charles Morris, ''Encyclopedia and unified science'', 1938, vol.1 n.1 * Charles Morris, ''Foundations of the theory of signs'', 1938, vol.1 n.2 *Victor Lenzen, ''Procedures of empirical sciences'', 1938, vol.1 n.5 * Rudolf Carnap, ''Foundations of logic and mathematics'', 1939, vol.1 n.3 *Leonard Bloomfield, ''Linguistic aspects of science'', 1939, vol.1 n.4 *
Ernest Nagel Ernest Nagel (November 16, 1901 – September 20, 1985) was an American philosopher of science. Along with Rudolf Carnap, Hans Reichenbach, and Carl Hempel, he is sometimes seen as one of the major figures of the logical positivism, logical posi ...
, ''Principles of the theory of probability'', 1939, vol.1 n.6 *John Dewey, ''Theory of valuation'', 1939, vol.2 n.4 *Giorgio de Santillana and Edgar Zilsel, ''The development of rationalism and empiricism'', 1941, vol.2 n.8 * Otto Neurath, ''Foundations of social sciences'', 1944, vol.2 n.1 *Joseph H. Woodger, ''The technique of theory construction'', 1949, vol.2 n.5 * Philipp Frank, ''Foundations of physics'', 1946, vol.1 n.7 *Erwin Finlay-Freundlich, ''Cosmology'', 1951, vol.1 n.8 *Jørgen Jørgensen, ''The development of logical empiricism'', 1951, vol.2 n.9 *Egon Brunswik, ''The conceptual framework of psychology'', 1952, vol.1 n.10 *Carl Hempel, ''Fundamentals of concept formation in empirical science'', 1952, vol.2 n.7 * Felix Mainx, ''Foundations of biology'', 1955, vol.1 n.9 *Abraham Edel, ''Science and the structure of ethics'', 1961, vol.2 n.3 *Thomas S. Kuhn, ''The structure of scientific revolutions'', 1962, vol.2 n.2 *Gerhard Tintner, ''Methodology of mathematical economics and econometrics'', 1968, vol.2 n.6 * Herbert Feigl and Charles Morris, ''Bibliography and index'', 1969, vol.2 n.10

# Topics and debates

The Vienna Circle cannot be assigned ''one'' single philosophy. First, there existed a plurality of philosophical positions within the Circle, and second, members often changed their views fundamentally in the course of time and in reaction to discussions in the Circle. It thus seems more convenient to speak of "the philosophies (in the plural) of the Vienna Circle". However, some central topics and debates can be identified.

## The Manifesto (1929)

This states the scientific world-conception of the Vienna Circle, which is characterized "essentially by two features. First it is empiricism, empiricist and positivist: there is knowledge only from experience. Second, the scientific world-conception is marked by the application of a certain method, namely logic, logical analysis." Logical analysis is the method of clarification of philosophical problems; it makes an extensive use of symbolic logic and distinguishes the Vienna Circle empiricism from earlier versions. The task of philosophy lies in the clarification—through the method of logical analysis—of problems and assertions. Logical analysis shows that there are two different kinds of statements; one kind includes statements reducible to simpler statements about the empirically given; the other kind includes statements which cannot be reduced to statements about experience and thus they are devoid of meaning. Metaphysics, Metaphysical statements belong to this second kind and therefore they are meaningless. Hence many philosophical problems are rejected as pseudo-problems which arise from logical mistakes, while others are re-interpreted as empirical statements and thus become the subject of scientific inquiries. One source of the logical mistakes that are at the origins of metaphysics is the ambiguity of natural language. "Ordinary language for instance uses the same part of speech, the substantive, for object (philosophy), things ('apple') as well as for Quality (philosophy), qualities ('hardness'), relations ('friendship'), and processes ('sleep'); therefore it misleads one into a thing-like conception of functional concepts". Another source of mistakes is "the notion that ''thinking'' can either lead to knowledge out of its own resources without using any empirical material, or at least arrive at new contents by an inference from given states of affair". synthetic proposition, Synthetic knowledge a priori is rejected by the Vienna Circle. Mathematics, which at a first sight seems an example of necessarily valid synthetic knowledge derived from pure reason alone, has instead a Tautology (logic), tautological character, that is its statements are analytic proposition, analytical statements, thus very different from Kantian synthetic statements. The only two kinds of statements accepted by the Vienna Circle are synthetic statements ''Empirical evidence, a posteriori'' (i.e., scientific statements) and analytic statements ''a priori and a posteriori, a priori'' (i.e., logical and mathematical statements). However, the persistence of metaphysics is connected not only with logical mistakes but also with "social and economical struggles".''VC'' p. 339 Metaphysics and theology are allied to traditional social forms, while the group of people who "faces modern times, rejects these views and takes its stand on the ground of empirical sciences". Thus the struggle between metaphysics and science, scientific world-conception is not only a struggle between different kinds of philosophies, but it is also—and perhaps primarily—a struggle between different political, social, and economical attitudes. Of course, as the manifesto itself acknowledged, "not every adherent of the scientific world-conception will be a fighter". Many historians of the Vienna Circle see in the latter sentence an implicit reference to a contrast between the so-called 'left wing' of the Vienna Circle, mainly represented by Neurath and Carnap, and Moritz Schlick. The aim of the left wing was to facilitate the penetration of the scientific world-conception in "the forms of personal and public life, in education, upbringing, architecture, and the shaping of economic and social life". In contrast, Schlick was primarily interested in the theoretical study of science and philosophy. Perhaps the sentence "Some, glad of solitude, will lead a withdrawn existence on the icy slopes of logic" is an ironic reference to Schlick. The manifesto lists Walter Dubislav, Josef Frank (architect), Josef Frank, Kurt Grelling, Hasso Härlen, Eino Kaila, Heinrich Loewy, F. P. Ramsey,
Hans Reichenbach Hans Reichenbach (September 26, 1891 – April 9, 1953) was a leading philosopher of science, educator, and proponent of logical empiricism. He was influential in the areas of science, education, and of logical empiricism. He founded the ''Gesell ...
,
Kurt Reidemeister Kurt Werner Friedrich Reidemeister (13 October 1893 – 8 July 1971) was a mathematician A mathematician is someone who uses an extensive knowledge of mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics ...
, and Edgar Zilsel as people "sympathetic to the Vienna Circle" 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 physicists of all time. Einstein is known for developing the theory of relativity The theo ...

,
Bertrand Russell Bertrand Arthur William Russell, 3rd Earl Russell (18 May 1872 – 2 February 1970) was a British polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose know ...
, and
Ludwig Wittgenstein Ludwig Josef Johann Wittgenstein ( ; ; 26 April 1889 – 29 April 1951) was an Austrian Austrian may refer to: * Austrians, someone from Austria or of Austrian descent ** Someone who is considered an Austrian citizen, see Austrian nationali ...

## Unified science

The final goal pursued by the Vienna Circle was Unified Science, unified science, that is the construction of a "constitutive system" in which every legitimate statement is reduced to the concepts of lower level which refer directly to the given experience. "The endeavour is to link and harmonise the achievements of individual investigators in their various fields of science". From this aim follows the search for clarity, neatness, and for a symbolic language that eliminates the problems arising from the ambiguity of natural language. The Vienna Circle published a collection, called ''Einheitswissenschaft'' (''Unified Science''), edited by Rudolf Carnap, Philipp Frank, Hans Hahn, Otto Neurath, Jørgen Jørgensen (after Hahn's death) and Charles W. Morris (from 1938), whose aim was to present a unified vision of science. After the publication in Europe of seven monographs from 1933 to 1939, the collection was dismissed, because of the problems arising from the World War II. In 1938 a new series of publications started in the United States. It was the ''
International Encyclopedia of Unified Science The ''International Encyclopedia of Unified Science'' (''IEUS'') was a series of publications devoted to unified science"Unified Science" can refer to any of three related strands in contemporary thought. * Belief in the unity of science was a cen ...
'', an ambitious project never completed devoted to unified science. Only the first section ''Foundations of the Unity of Sciences'' was published; it contains two volumes for a total of twenty monographs published from 1938 to 1969. As remembered by Rudolf Carnap and Charles Morris in the ''Preface'' to the 1969 edition of the International Encyclopedia of Unified Science: Thomas Kuhn's well known work, ''The Structure of Scientific Revolutions'', was published in this Encyclopedia in 1962, as the number two in the second volume.

## Critique of metaphysics

The attitude of Vienna Circle towards metaphysics is well expressed by Carnap in the article 'Überwindung der Metaphysik durch Logische Analyse der Sprache' in ''Erkenntnis'', vol. 2, 1932 (English translation 'The Elimination of Metaphysics Through Logical Analysis of Language' in Sarkar, Sahotra, ed., ''Logical empiricism at its peak: Schlick, Carnap, and Neurath'', New York : Garland Pub., 1996, pp. 10–31). A language—says Carnap—consists of a vocabulary, i.e., a set of meaningful words, and a syntax, i.e., a set of rules governing the formation of sentences from the words of the vocabulary. Pseudo-statements, i.e., sequences of words that at first sight resemble statements but in reality have no meaning, are formed in two ways: either meaningless words occur in them, or they are formed in an invalid syntactical way. According to Carnap, pseudo-statements of both kinds occur in metaphysics. A word ''W'' has a meaning if two conditions are satisfied. First, the mode of the occurrence of ''W'' in its elementary sentence form (i.e., the simplest sentence form in which ''W'' is capable of occurring) must be fixed. Secondly, if ''W'' occurs in an elementary sentence ''S'', it is necessary to give an answer to the following questions (that are—according to Carnap—equivalent formulation of the same question): * What Sentence (linguistics), sentences is ''S'' deducible from, and what sentences are deducible from ''S''? * Under what conditions is ''S'' supposed to be true, and under what conditions false? * How is ''S'' verified? * What is the meaning of ''S''? (Carnap, "The Elimination of Metaphysics Through Logical Analysis of Language" in Sarkar, Sahotra 1996, p. 12) An example offered by Carnap concerns the word 'arthropod'. The sentence form "the thing ''x'' is an arthropod" is an elementary sentence form that is derivable from "''x'' is an animal", "''x'' has a segmented body" and "''x'' has jointed legs". Conversely, these sentences are derivable from "the thing ''x'' is an arthropod". Thus the meaning of the word 'arthropod' is determined. According to Carnap, many words of metaphysics do not fulfill these requirements and thus they are meaningless. As an example, Carnap considers the word 'principle'. This word has a definite meaning, if the sentence "''x'' is the principle of ''y''" is supposed to be equivalent to the sentence "''y'' exists by virtue of ''x''" or "''y'' arises out of ''x''". The latter sentence is perfectly clear: ''y'' arises out of ''x'' when ''x'' is invariably followed by ''y'', and the invariable association between ''x'' and ''y'' is empirically verifiable. But—says Carnap—metaphysicians are not satisfied with this interpretation of the meaning of 'principle'. They assert that no empirical relation between ''x'' and ''y'' can completely explain the meaning of "''x'' is the principle of ''y''", because there is something that cannot be grasped by means of the experience, something for which no empirical criterion can be specified. It is the lacking of any empirical criterion—says Carnap—that deprives of meaning the word 'principle' when it occurs in metaphysics. Therefore, metaphysical pseudo-statements such as "water is the principle of the world" or "the spirit is the principle of the world" are void of meaning because a meaningless word occurs in them. However, there are pseudo-statements in which occur only meaningful words; these pseudo-statements are formed in a counter-syntactical way. An example is the word sequence "Caesar is a prime number"; every word has a definite meaning, but the sequence has no meaning. The problem is that "prime number" is a predicate of numbers, not a predicate of human beings. In the example the nonsense is evident; however, in natural language the rules of grammar do not prohibit the formation of analogous meaningless word sequences that are not so easily detectable. In the grammar of natural languages, every sequence of the kind "''x'' is ''y''", where ''x'' is a noun and ''y'' is a predicate, is acceptable. In fact, in the grammar there is no distinction between predicate which can be affirmed of human beings and predicate which can be affirmed of numbers. So "Caesar is a general" and "Caesar is a prime number" are both well-formed, in contrast for example with "Caesar is and", which is ill-formed. In a logically constructed language—says Carnap—a distinction between the various kinds of predicate is specified, and pseudo-statements as "Caesar is a prime number" are ill-formed. Now, and this is the main point of Carnap's argument, metaphysical statements in which meaningless words do not occur, are indeed meaningless because they are formed in a way which is admissible in natural languages, but not in logically constructed languages. Carnap attempts to indicate the most frequent sources of errors from which metaphysical pseudo-statements can arise. One source of mistakes is the ambiguity of the verb "to be", which is sometimes used as a Copula (linguistics), copula ("I am hungry"), and sometimes to designate existence ("I am"). The latter statement incorrectly suggests a predicative form, and thus it suggests that existence is a predicate. Only modern logic, with the introduction of an explicit sign to designate existence (the sign $\exists \;$), which occurs only in statements such as $\exists \;xP\left(x\right)$, never as a predicate, has shown that existence is not a predicate, and thus has revealed the logical error from which pseudo-statements such as "cogito, ergo sum" has arisen. Another source of mistakes is type confusions, in which a predicate of a kind is used as a predicate of another kind. For example, the pseudo-statements "we know the Nothing" is analogous to "we know the rain", but while the latter is well-formed, the former is ill-formed, at least in a logically constructed language, because "Nothing" is incorrectly used as a noun. In a formal language, "Nothing" only means $\lnot \;\exists \;x$, such as "there is nothing which is outside"—i.e., $\lnot \;\exists \;xO\left(x\right)$, and thus "Nothing" never occurs as a noun or as a predicate. According to Carnap, although metaphysics has no theoretical content, it does have content: metaphysical pseudo-statements express the attitude of a person towards life, and this is the role of metaphysics. He compares it to an art like lyrical poetry; the metaphysician works with the medium of the theoretical; he confuses art with science, attitude towards life with knowledge, and thus produces an unsatisfactory and inadequate work. "Metaphysicians are musicians without musical ability".

# Institute Vienna Circle / Vienna Circle Society

In 1991 the Institute Vienna Circle, Institute Vienna Circle (IVC) was established as a society in Vienna. It is dedicated to studying the work and influence of the Vienna Circle. In 2011 it was integrated in the
University of Vienna The University of Vienna (german: Universität Wien) is a public university, public research university located in Vienna, Austria. It was founded by Rudolf IV, Duke of Austria, Duke Rudolph IV in 1365 and is the oldest university in the Geograph ...
as a subunit of the Faculty of Philosophy and Education. Since 2016 the former society continues its activities in close cooperation with the IVC under the changed name Vienna Circle Society (VCS). In 2015 the Institute co-organized an exhibition on the Vienna Circle in the main building of the University of Vienna.

* Formalism (mathematics) * Logical behaviorism * Logicism * List of Austrian intellectual traditions

# Bibliography

## Primary literature

* Carnap, Rudolf. "Überwindung der Metaphysik durch Logische Analyse der Sprache" in ''Erkenntnis'', vol. 2, 1932 (English translation "The Elimination of Metaphysics Through Logical Analysis of Language" in Sarkar, Sahotra, ed., ''Logical empiricism at its peak: Schlick, Carnap, and Neurath'', New York : Garland Pub., 1996, pp. 10–31) * Neurath, Otto and Carnap, Rudolf and Morris, Charles W. ''Foundations of the Unity of Sciences'', vol. 1, Chicago : The University of Chicago Press, 1969. * ''Wissenschaftliche Weltauffassung. Der Wiener Kreis'', 1929. English translation ''The Scientific Conception of the World. The Vienna Circle'' in Sarkar, Sahotra, ed., ''The Emergence of Logical Empiricism: from 1900 to the Vienna Circle'', New York : Garland Publishing, 1996, pp. 321–340 * Stadler, Friedrich and Uebel, Thomas (eds.): ''Wissenschaftliche Weltauffassung. Der Wiener Kreis. Hrsg. vom Verein Ernst Mach (1929).'' Reprint of the first edition. With translations into English, French, Spanish and Italian. Vienna: Springer, 2012. * Stöltzner, Michael and Uebel, Thomas (eds.). ''Wiener Kreis. Texte zur wissenschaftlichen Weltauffassung''. Meiner, Hamburg, 2006, . (Anthology in German)

## Secondary literature

* Arnswald, Ulrich, Friedrich Stadler, Stadler, Friedrich and Weibel, Peter (ed.): ''Der Wiener Kreis – Aktualität in Wissenschaft, Literatur, Architektur und Kunst.'' Wien: LIT Verlag 2019. * Ayer, Alfred Jules. ''Language, Truth and Logic.'' London, Victor Gollancz, 1936. * Ayer, Alfred Jules. ''Logical Positivism''. Glencoe, Ill: Free Press, 1959. * Barone, Francesco. ''Il neopositivismo logico''. Roma Bari: Laterza, 1986. * Gustav Bergmann, Bergmann, Gustav. ''The Metaphysics of Logical Positivism''. New York: Longmans Green, 1954. * Cirera, Ramon. ''Carnap and the Vienna Circle: Empiricism and Logical Syntax''. Atlanta, GA: Rodopi, 1994. * * Philipp Frank, Frank, Philipp: ''Modern Science and its Philosophy''. Cambridge, 1949. * Michael Friedman (philosopher), Friedman, Michael, ''Reconsidering Logical Positivism''. Cambridge, UK: Cambridge University Press, 1999. * Gadol, Eugene T. ''Rationality and Science: A Memorial Volume for Moritz Schlick in Celebration of the Centennial of his Birth''. Wien: Springer, 1982. * Ludovico Geymonat, Geymonat, Ludovico. ''La nuova filosofia della natura in Germania''. Torino, 1934. * Ronald Giere, Giere, Ronald N. and Richardson, Alan W. ''Origins of Logical Empiricism''. Minneapolis: University of Minnesota Press, 1997. * Haller, Rudolf. ''Neopositivismus. Eine historische Einführung in die Philosophie des Wiener Kreises''. Wissenschaftliche Buchgesellschaft, Darmstadt, 1993, . (German) * Jim Holt (philosopher), Holt, Jim. "Positive Thinking" (review of Karl Sigmund, ''Exact Thinking in Demented Times: The Vienna Circle and the Epic Quest for the Foundations of Science'', Basic Books, 449 pp.), ''The New York Review of Books'', vol. LXIV, no. 20 (21 December 2017), pp. 74–76. * Victor Kraft, Kraft, Victor. ''The Vienna Circle: The Origin of Neo-positivism, a Chapter in the History of Recent Philosophy''. New York: Greenwood Press, 1953. * Limbeck, Christoph and Stadler, Friedrich (eds.). ''The Vienna Circle. Texts and Pictures of an Exhibition.'' Münster-Berlin-London 2015. * Brian McGuinness, McGuinness, Brian. ''Wittgenstein and the Vienna Circle: Conversations Recorded by Friedrich Waismann''. Trans. by Joachim Schulte and Brian McGuinness. New York: Barnes & Noble Books, 1979. * Parrini, Paolo; Wesley C. Salmon, Salmon, Wesley C.; Salmon, Merrilee H. (ed.) ''Logical Empiricism – Historical and Contemporary Perspectives'', Pittsburgh: University of Pittsburgh Press, 2003. * Reisch, George. ''How the Cold War Transformed Philosophy of Science : To the Icy Slopes of Logic''. New York: Cambridge University Press, 2005. * Nicholas Rescher, Rescher, Nicholas (ed.). ''The Heritage of Logical Positivism''. University Press of America, 1985. * Richardson, Alan W. "The Scientific World Conception. Logical Positivism", in: T. Baldwin (Hg.), ''The Cambridge History of Philosophy'', 1870–1945, 2003, 391–400. * Richardson, Alan W. and Uebel, Thomas (ed.). ''The Cambridge Companion to Logical Empiricism''. Cambridge, 2007. * Salmon, Wesley and Wolters, Gereon (ed.), ''Logic, Language, and the Structure of Scientific Theories: Proceedings of the Carnap-Reichenbach Centennial, University of Konstanz, 21–24 May 1991'', Pittsburgh: University of Pittsburgh Press, 1994. * Sahotra Sarkar, Sarkar, Sahotra. ''The Emergence of Logical Empiricism: From 1900 to the Vienna Circle''. New York: Garland Publishing, 1996. * Sarkar, Sahotra. ''Logical Empiricism at its Peak: Schlick, Carnap, and Neurath''. New York: Garland Pub., 1996. * Sarkar, Sahotra. ''Logical Empiricism and the Special Sciences: Reichenbach, Feigl, and Nagel''. New York: Garland Pub., 1996. * Sarkar, Sahotra. ''Decline and Obsolescence of Logical Empiricism: Carnap vs. Quine and the Critics''. New York: Garland Pub., 1996. * Sarkar, Sahotra. ''The Legacy of the Vienna Circle: Modern Reappraisals''. New York: Garland Pub., 1996. * Wolfgang Spohn, Spohn, Wolfgang (ed.), ''Erkenntnis Orientated: A Centennial Volume for Rudolf Carnap and Hans Reichenbach'', Boston: Kluwer Academic Publishers, 1991. * Friedrich Stadler, Stadler, Friedrich. ''The Vienna Circle. Studies in the Origins, Development, and Influence of Logical Empiricism.'' New York: Springer, 2001. – 2nd Edition: Dordrecht: Springer, 2015. * Stadler, Friedrich (ed.). ''The Vienna Circle and Logical Empiricism. Re-evaluation and Future Perspectives.'' Dordrecht – Boston London, Kluwer, 2003. * Thomas Uebel, Uebel, Thomas. ''Vernunftkritik und Wissenschaft: Otto Neurath und der erste Wiener Kreis.'' Wien-New York 2000. (German) * Uebel, Thomas, "On the Austrian Roots of Logical Empiricism" in ''Logical Empiricism – Historical and contemporary Perspectives'', ed. Paolo Parrini, Wesley C. Salmon, Merrilee H. Salmon, Pittsburgh : University of Pittsburgh Press, 2003, pp. 76–93.