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Rudolf Carnap (; ; 18 May 1891 – 14 September 1970) was a German-language philosopher who was active in
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before 1935 and in the
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thereafter. He was a major member of the
Vienna Circle The Vienna Circle () of logical empiricism was a group of elite philosophers and scientists drawn from the natural and social sciences, logic and mathematics who met regularly from 1924 to 1936 at the University of Vienna, chaired by Moritz Sc ...
and an advocate of
logical positivism Logical positivism, also known as logical empiricism or neo-positivism, was a philosophical movement, in the empiricist tradition, that sought to formulate a scientific philosophy in which philosophical discourse would be, in the perception of ...
.


Biography

Carnap's father rose from being a poor ribbon-weaver to be the owner of a ribbon-making factory. His mother came from an academic family; her father was an educational reformer and her oldest brother was the
archaeologist Archaeology or archeology is the study of human activity through the recovery and analysis of material culture. The archaeological record consists of Artifact (archaeology), artifacts, architecture, biofact (archaeology), biofacts or ecofacts, ...
Wilhelm Dörpfeld Wilhelm Dörpfeld (26 December 1853 – 25 April 1940) was a German architect and archaeologist, a pioneer of stratigraphy, stratigraphic excavation and precise graphical documentation of archaeological projects. He is famous for his work on B ...
. As a ten-year-old, Carnap accompanied Wilhelm Dörpfeld on an expedition to Greece. Carnap was raised in a profoundly religious
Protestant Protestantism is a branch of Christianity that emphasizes Justification (theology), justification of sinners Sola fide, through faith alone, the teaching that Salvation in Christianity, salvation comes by unmerited Grace in Christianity, divin ...
family, but later became an atheist. He began his formal education at the
Barmen Barmen is a former industrial metropolis of the region of Bergisches Land, Germany, which merged with four other towns in 1929 to form the city of Wuppertal. Barmen, together with the neighbouring town of Elberfeld founded the first electric ...
Gymnasium and the Gymnasium in
Jena Jena (; ) is a List of cities and towns in Germany, city in Germany and the second largest city in Thuringia. Together with the nearby cities of Erfurt and Weimar, it forms the central metropolitan area of Thuringia with approximately 500,000 in ...
. From 1910 to 1914, he attended the
University of Jena The University of Jena, officially the Friedrich Schiller University Jena (, abbreviated FSU, shortened form ''Uni Jena''), is a public research university located in Jena, Thuringia, Germany. The university was established in 1558 and is cou ...
, intending to write a thesis in
physics Physics is the scientific study of matter, its Elementary particle, 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 whi ...
. He also intently studied
Immanuel Kant Immanuel Kant (born Emanuel Kant; 22 April 1724 – 12 February 1804) was a German Philosophy, philosopher and one of the central Age of Enlightenment, Enlightenment thinkers. Born in Königsberg, Kant's comprehensive and systematic works ...
's ''
Critique of Pure Reason The ''Critique of Pure Reason'' (; 1781; second edition 1787) is a book by the German philosopher Immanuel Kant, in which the author seeks to determine the limits and scope of metaphysics. Also referred to as Kant's "First Critique", it was foll ...
'' during a course taught by Bruno Bauch, and was one of the very few students to attend
Gottlob Frege Friedrich Ludwig Gottlob Frege (; ; 8 November 1848 – 26 July 1925) was a German philosopher, logician, and mathematician. He was a mathematics professor at the University of Jena, and is understood by many to be the father of analytic philos ...
's courses in
mathematical logic Mathematical logic is the study of Logic#Formal logic, formal logic within mathematics. Major subareas include model theory, proof theory, set theory, and recursion theory (also known as computability theory). Research in mathematical logic com ...
. During his university years, he became enthralled with the
German Youth Movement The German Youth Movement () is a collective term for a cultural and educational movement that started in 1896. It consists of numerous associations of young people that focus on outdoor activities. The movement included German Scouting and the ...
. While Carnap held moral and political opposition to
World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
, he felt obligated to serve in the German army. After three years of service, he was given permission to study physics at the
University of Berlin The Humboldt University of Berlin (, abbreviated HU Berlin) is a public research university in the central borough of Mitte in Berlin, Germany. The university was established by Frederick William III on the initiative of Wilhelm von Humbol ...
, 1917–18, where
Albert Einstein Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...
was a newly appointed professor. Carnap then attended the
University of Jena The University of Jena, officially the Friedrich Schiller University Jena (, abbreviated FSU, shortened form ''Uni Jena''), is a public research university located in Jena, Thuringia, Germany. The university was established in 1558 and is cou ...
, where he wrote a thesis defining an
axiomatic theory In mathematics and logic, an axiomatic system is a set of formal statements (i.e. axioms) used to logically derive other statements such as lemmas or theorems. A proof within an axiom system is a sequence of deductive steps that establishes ...
of
space Space is a three-dimensional continuum containing positions and directions. In classical physics, physical space is often conceived in three linear dimensions. Modern physicists usually consider it, with time, to be part of a boundless ...
and
time Time is the continuous progression of existence that occurs in an apparently irreversible process, irreversible succession from the past, through the present, and into the future. It is a component quantity of various measurements used to sequ ...
. The physics department said it was too philosophical, and Bruno Bauch of the philosophy department said it was pure physics. Carnap then wrote another thesis in 1921, under Bauch's supervision, on the theory of space in a more orthodox
Kant Immanuel Kant (born Emanuel Kant; 22 April 1724 – 12 February 1804) was a German philosopher and one of the central Enlightenment thinkers. Born in Königsberg, Kant's comprehensive and systematic works in epistemology, metaphysics, et ...
ian style, published as ''Der Raum'' (''Space'') in a supplemental issue of '' Kant-Studien'' (1922). Frege's course exposed him to
Bertrand Russell Bertrand Arthur William Russell, 3rd Earl Russell, (18 May 1872 – 2 February 1970) was a British philosopher, logician, mathematician, and public intellectual. He had influence on mathematics, logic, set theory, and various areas of analytic ...
's work on logic and philosophy, which gave a sense of direction to his studies. He accepted the effort to surpass traditional philosophy with logical innovations that inform the sciences. He wrote a letter to Russell, who responded by copying by hand long passages from his ''
Principia Mathematica The ''Principia Mathematica'' (often abbreviated ''PM'') is a three-volume work on the foundations of mathematics written by the mathematician–philosophers Alfred North Whitehead and Bertrand Russell and published in 1910, 1912, and 1 ...
'' for Carnap's benefit, as neither Carnap nor his university could afford a copy of this epochal work. In 1924 and 1925, he attended seminars led by
Edmund Husserl Edmund Gustav Albrecht Husserl (; 8 April 1859 – 27 April 1938) was an Austrian-German philosopher and mathematician who established the school of Phenomenology (philosophy), phenomenology. In his early work, he elaborated critiques of histori ...
, the founder of
phenomenology Phenomenology may refer to: Art * Phenomenology (architecture), based on the experience of building materials and their sensory properties Philosophy * Phenomenology (Peirce), a branch of philosophy according to Charles Sanders Peirce (1839� ...
, and continued to write on physics from a
logical positivist Logical positivism, also known as logical empiricism or neo-positivism, was a philosophical movement, in the empiricist tradition, that sought to formulate a scientific philosophy in which philosophical discourse would be, in the perception of ...
perspective. Carnap discovered a kindred spirit when he met
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 ''G ...
at a 1923 conference. Reichenbach introduced Carnap to
Moritz Schlick Friedrich Albert Moritz Schlick (; ; 14 April 1882 – 22 June 1936) was a German philosopher, physicist, and the founding father of logical positivism and the Vienna Circle. He was murdered by a former student, Johann Nelböck, in 1936. Early ...
, a professor at the
University of Vienna The University of Vienna (, ) is a public university, public research university in Vienna, Austria. Founded by Rudolf IV, Duke of Austria, Duke Rudolph IV in 1365, it is the oldest university in the German-speaking world and among the largest ...
who offered Carnap a position in his department, which Carnap accepted in 1926. Carnap thereupon joined an informal group of Viennese intellectuals that came to be known as the
Vienna Circle The Vienna Circle () of logical empiricism was a group of elite philosophers and scientists drawn from the natural and social sciences, logic and mathematics who met regularly from 1924 to 1936 at the University of Vienna, chaired by Moritz Sc ...
, directed largely by Schlick and including Hans Hahn,
Friedrich Waismann Friedrich Waismann (; ; 21 March 18964 November 1959) was an Austrian mathematician, physicist, and philosopher. He is best known for being a member of the Vienna Circle and one of the key theorists in logical positivism. Biography Born to a ...
,
Otto Neurath Otto Karl Wilhelm Neurath (; ; 10 December 1882 – 22 December 1945) was an Austrian-born philosopher of science, sociologist, and political economist. He was also the inventor of the ISOTYPE method of pictorial statistics and an innovator in ...
, and
Herbert Feigl Herbert Feigl (; ; December 14, 1902 – June 1, 1988) was an Austrian- American philosopher and an early member of the Vienna Circle. He coined the term " nomological danglers". Biography The son of a trained weaver who became a textile designer ...
, with occasional visits by Hahn's student
Kurt Gödel Kurt Friedrich Gödel ( ; ; April 28, 1906 – January 14, 1978) was a logician, mathematician, and philosopher. Considered along with Aristotle and Gottlob Frege to be one of the most significant logicians in history, Gödel profoundly ...
. When
Wittgenstein Ludwig Josef Johann Wittgenstein ( ; ; 26 April 1889 – 29 April 1951) was an Austrian philosopher who worked primarily in logic, the philosophy of mathematics, the philosophy of mind, and the philosophy of language. From 1929 to 1947, Witt ...
visited Vienna, Carnap would meet with him. He (with Hahn and Neurath) wrote the 1929 manifesto of the Circle, and (with
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 ''G ...
) initiated the philosophy journal ''
Erkenntnis ''Erkenntnis'' is a journal of philosophy that publishes papers in analytic philosophy. Its name is derived from the German word " Erkenntnis", meaning "knowledge, recognition". The journal was also linked to organisation of conferences, such as th ...
''. In February 1930,
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 ...
lectured in Vienna, and during November 1930, Carnap visited Warsaw. On these occasions, he learned much about Tarski's model-theoretic method of
semantics Semantics is the study of linguistic Meaning (philosophy), meaning. It examines what meaning is, how words get their meaning, and how the meaning of a complex expression depends on its parts. Part of this process involves the distinction betwee ...
. Rose Rand, another philosopher in the Vienna Circle, noted, "Carnap's conception of semantics starts from the basis given in Tarski's work, but a distinction is made between logical and non-logical constants, and between logical and factual truth... At the same time, he worked with the concepts of intension and extension, and took these two concepts as a basis of a new method of semantics." In 1931, Carnap was appointed Professor at the German University of Prague. In 1933,
W. V. Quine Willard Van Orman Quine ( ; known to his friends as "Van"; June 25, 1908 – December 25, 2000) was an American philosopher and logician in the analytic tradition, recognized as "one of the most influential philosophers of the twentieth centur ...
met Carnap in Prague and discussed the latter's work at some length. Thus began the lifelong mutual respect these two men shared, one that survived Quine's eventual forceful disagreements with a number of Carnap's philosophical conclusions. Carnap, whose
socialist Socialism is an economic ideology, economic and political philosophy encompassing diverse Economic system, economic and social systems characterised by social ownership of the means of production, as opposed to private ownership. It describes ...
and
pacifist Pacifism is the opposition to war or violence. The word ''pacifism'' was coined by the French peace campaigner Émile Arnaud and adopted by other peace activists at the tenth Universal Peace Congress in Glasgow in 1901. A related term is ''a ...
beliefs put him at risk in
Nazi Germany Nazi Germany, officially known as the German Reich and later the Greater German Reich, was the German Reich, German state between 1933 and 1945, when Adolf Hitler and the Nazi Party controlled the country, transforming it into a Totalit ...
, emigrated to the United States in 1935 and became a
naturalized citizen Naturalization (or naturalisation) is the legal act or process by which a non-national of a country acquires the nationality of that country after birth. The definition of naturalization by the International Organization for Migration of the ...
in 1941. Meanwhile, back in Vienna, Schlick was murdered in 1936. From 1936 to 1952, Carnap was a professor of philosophy at the
University of Chicago The University of Chicago (UChicago, Chicago, or UChi) is a Private university, private research university in Chicago, Illinois, United States. Its main campus is in the Hyde Park, Chicago, Hyde Park neighborhood on Chicago's South Side, Chic ...
. During the late 1930s, Carnap offered an assistant position in philosophy to
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 positivism, logical empiricism, a 20th-century movement in the philosophy ...
, who accepted and became one of his most significant intellectual collaborators. Thanks partly to Quine's help, Carnap spent the years 1939–41 at
Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...
, where he was reunited with Tarski. Carnap (1963) later expressed some irritation about his time at Chicago, where he and Charles W. Morris were the only members of the department committed to the primacy of science and logic. (Their Chicago colleagues included
Richard McKeon Richard McKeon (; April 26, 1900 – March 31, 1985) was an American philosopher and longtime professor at the University of Chicago. His ideas formed the basis for the UN's Universal Declaration of Human Rights. Life, times, and influences McKeo ...
,
Charles Hartshorne Charles Hartshorne (; June 5, 1897 – October 9, 2000) was an American philosopher who concentrated primarily on the philosophy of religion and metaphysics, but also contributed to ornithology. He developed the neoclassical idea of God and ...
, and Manley Thompson.) Carnap's years at Chicago were nonetheless very productive ones. He wrote books on
semantics Semantics is the study of linguistic Meaning (philosophy), meaning. It examines what meaning is, how words get their meaning, and how the meaning of a complex expression depends on its parts. Part of this process involves the distinction betwee ...
(Carnap 1942, 1943, 1956),
modal logic Modal logic is a kind of logic used to represent statements about Modality (natural language), necessity and possibility. In philosophy and related fields it is used as a tool for understanding concepts such as knowledge, obligation, and causality ...
, and on the philosophical foundations of
probability Probability is a branch of mathematics and statistics concerning events and numerical descriptions of how likely they are to occur. The probability of an event is a number between 0 and 1; the larger the probability, the more likely an e ...
and
inductive logic Inductive reasoning refers to a variety of methods of reasoning in which the conclusion of an argument is supported not with deductive certainty, but with some degree of probability. Unlike ''deductive'' reasoning (such as mathematical inducti ...
(Carnap 1950, 1952). After a stint at the
Institute for Advanced Study The Institute for Advanced Study (IAS) is an independent center for theoretical research and intellectual inquiry located in Princeton, New Jersey. It has served as the academic home of internationally preeminent scholars, including Albert Ein ...
in Princeton (1952–1954), he joined the
UCLA The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California, United States. Its academic roots were established in 1881 as a normal school then known as the southern branch of the C ...
Department of Philosophy in 1954,
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 ''G ...
having died the previous year. He had earlier refused an offer of a similar job at the
University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...
, because accepting that position required that he sign a
loyalty oath Loyalty is a Fixation (psychology), devotion to a country, philosophy, group, or person. Philosophers disagree on what can be an object of loyalty, as some argue that loyalty is strictly interpersonal and only another human being can be the obj ...
, a practice to which he was opposed on principle. While at UCLA, he wrote on scientific knowledge, the
analytic–synthetic distinction The analytic–synthetic distinction is a semantic distinction used primarily in philosophy to distinguish between propositions (in particular, statements that are affirmative subject– predicate judgments) that are of two types: analytic propos ...
, and the verification principle. His writings on
thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed b ...
and on the foundations of probability and
inductive logic Inductive reasoning refers to a variety of methods of reasoning in which the conclusion of an argument is supported not with deductive certainty, but with some degree of probability. Unlike ''deductive'' reasoning (such as mathematical inducti ...
were published posthumously as Carnap (1971, 1977, 1980). Carnap taught himself
Esperanto Esperanto (, ) is the world's most widely spoken Constructed language, constructed international auxiliary language. Created by L. L. Zamenhof in 1887 to be 'the International Language' (), it is intended to be a universal second language for ...
when he was 14 years of age. He later attended the
World Congress of Esperanto The World Esperanto Congress (, UK) is an annual Esperanto convention. It has the longest tradition among international Esperanto conventions, with an almost unbroken run for 119 years. The congresses have been held since August 5, 1905, every ye ...
in Dresden in 1908. He also attended the 1924 Congress in Vienna, where he met his fellow Esperantist
Otto Neurath Otto Karl Wilhelm Neurath (; ; 10 December 1882 – 22 December 1945) was an Austrian-born philosopher of science, sociologist, and political economist. He was also the inventor of the ISOTYPE method of pictorial statistics and an innovator in ...
for the first time. In the USA, Carnap was somewhat politically involved. Carnap was a signatory of an open appeal distributed by the National Committee to Secure Justice in the Rosenberg Case to appeal for clemency in the case. He was listed as a 'sponsor' for the "National Conference to Appeal the Walter-McCarran Law and Defend Its Victims" organised by the American Committee for the Protection of the Foreign Born, and also for the "Scientific and Cultural Conference for World Peace" organised by the
National Council of Arts, Sciences and Professions The National Council of (the) Arts, Sciences and Professions (NCASP or ASP) was a United States–based socialist organization of the 1950s. Entertainment trade publication ''Box Office'' characterized the ASP as, "an independent organization to su ...
. Carnap had four children by his first marriage to Elizabeth Schöndube, which ended in divorce in 1929. He married his second wife, Elizabeth Ina Stöger, in 1933. Ina committed suicide in 1964.


Philosophical work

Below is an examination of the main topics in the evolution of the philosophy of Rudolf Carnap. It is not exhaustive, but it outlines Carnap's main works and contributions to modern
epistemology Epistemology is the branch of philosophy that examines the nature, origin, and limits of knowledge. Also called "the theory of knowledge", it explores different types of knowledge, such as propositional knowledge about facts, practical knowle ...
and
philosophy of logic Philosophy of logic is the area of philosophy that studies the scope and nature of logic. It investigates the philosophical problems raised by logic, such as the presuppositions often implicitly at work in theories of logic and in their applicatio ...
.


''Der Raum''

From 1919 to 1921, Carnap worked on a doctoral thesis called ''Der Raum: Ein Beitrag zur Wissenschaftslehre'' (''Space: A Contribution to the Theory of Science'', 1922). In this dissertation on the philosophical foundations of geometry, Carnap tried to provide a logical basis for a theory of space and time in physics. Considering that Carnap was interested in
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 ...
,
natural sciences Natural science or empirical science is one of the branches of science concerned with the description, understanding and prediction of natural phenomena, based on empirical evidence from observation and experimentation. Mechanisms such as peer ...
and philosophy, his dissertation can be seen as an attempt to build a bridge between the different disciplines that are geometry, physics, and philosophy. For Carnap thought that in many instances those disciplines use the same concepts, but with totally different meanings. The main objective of Carnap's dissertation was to show that the inconsistencies between theories concerning space only existed because philosophers, as well as mathematicians and scientists, were talking about different things while using the same "space" word. Hence, Carnap characteristically argued that there had to be three separate notions of space. "Formal" space is space in the sense of mathematics: it is an abstract system of relations. "Intuitive" space is made of certain contents of intuition independent of single experiences. "Physical" space is made of actual spatial facts given in experience. The upshot is that those three kinds of "space" imply three different kinds of knowledge and thus three different kinds of investigations. It is interesting to note that it is in this dissertation that the main themes of Carnap's philosophy appear, most importantly, the idea that many philosophical contradictions appear because of a misuse of language, and a stress on the importance of distinguishing formal and material modes of speech.


''Der Logische Aufbau der Welt''

From 1922 to 1925, Carnap worked on a book which became one of his major works, namely ''Der logische Aufbau der Welt'' (translated as ''The Logical Structure of the World'', 1967), which was accepted in 1926 as his
habilitation Habilitation is the highest university degree, or the procedure by which it is achieved, in Germany, France, Italy, Poland and some other European and non-English-speaking countries. The candidate fulfills a university's set criteria of excelle ...
thesis at the
University of Vienna The University of Vienna (, ) is a public university, public research university in Vienna, Austria. Founded by Rudolf IV, Duke of Austria, Duke Rudolph IV in 1365, it is the oldest university in the German-speaking world and among the largest ...
and published as a book in 1928. That achievement has become a landmark in modern epistemology and can be read as a forceful statement of the philosophical thesis of logical positivism. Indeed, the ''Aufbau'' suggests that epistemology, based on modern
symbolic logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the study of deductively valid inferences or logical truths. It examines how conclusions follow from premises based on the structure o ...
, is concerned with the logical analysis of scientific propositions, while science itself, based on experience, is the only source of knowledge of the external world, i.e. the world outside the realm of human perception. According to Carnap, philosophical propositions are statements about the language of science; they aren't true or false, but merely consist of definitions and conventions about the use of certain concepts. In contrast, scientific propositions are factual statements about the external reality. They are meaningful because they are based on the perceptions of the senses. In other words, the truth or falsity of those propositions can be verified by testing their content with further observations. In the ''Aufbau'', Carnap wants to display the logical and conceptual structure with which all scientific (factual) statements can be organized. Carnap gives the label "constitution theory" to this epistemic-logical project. It is a constructive undertaking that systematizes scientific knowledge according to the notions of symbolic logic. Accordingly, the purpose of this constitutional system is to identify and discern different classes of scientific concepts and to specify the logical relations that link them. In the Aufbau, concepts are taken to denote objects, relations, properties, classes and states. Carnap argues that all concepts must be ranked over a hierarchy. In that hierarchy, all concepts are organized according to a fundamental arrangement where concepts can be reduced and converted to other basic ones. Carnap explains that a concept can be reduced to another when all sentences containing the first concept can be transformed into sentences containing the other. In other words, every scientific sentence should be translatable into another sentence such that the original terms have the same reference as the translated terms. Most significantly, Carnap argues that the basis of this system is psychological. Its content is the "immediately given", which is made of basic elements, namely perceptual experiences. These basic elements consist of conscious psychological states of a single human subject. In the end, Carnap argues that his constitutional project demonstrates the possibility of defining and uniting all scientific concepts in a single conceptual system on the basis of a few fundamental concepts.


Overcoming metaphysics

From 1928 to 1934, Carnap published papers (''Scheinprobleme in der Philosophie'', 1928; translated as ''Pseudoproblems in Philosophy'', 1967) in which he appears overtly skeptical of the aims and methods of
metaphysics Metaphysics is the branch of philosophy that examines the basic structure of reality. It is traditionally seen as the study of mind-independent features of the world, but some theorists view it as an inquiry into the conceptual framework of ...
, i.e. the traditional philosophy that finds its roots in mythical and religious thought. Indeed, he discusses how, in many cases, metaphysics is made of meaningless discussions of pseudo-problems. For Carnap, a pseudo-problem is a philosophical question that, on the surface, handles concepts that refer to our world while, in fact, these concepts do not actually denote real and attested objects. In other words, these pseudo-problems concern statements that do not, in any way, have empirical implications. They do not refer to states of affairs and the things they denote cannot be perceived. Consequently, one of Carnap's main aim has been to redefine the purpose and method of philosophy. According to him, philosophy should not aim at producing any knowledge transcending the knowledge of science. In contrast, by analyzing the language and propositions of science, philosophers should define the logical foundations of scientific knowledge. Using
symbolic logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the study of deductively valid inferences or logical truths. It examines how conclusions follow from premises based on the structure o ...
, they should explicate the concepts, methods, and justificatory processes that exist in science. Carnap believed that the difficulty with traditional philosophy lay in the use of concepts that are not useful for science. For Carnap, the scientific legitimacy of these concepts was doubtful because the sentences containing them do not express facts. Indeed, a logical analysis of those sentences proves that they do not convey the meaning of states of affairs. In other words, these sentences are meaningless. Carnap explains that to be meaningful, a sentence should be factual. It can be so, for one thing, by being based on experience, i.e., by being formulated with words relating to direct observations. For another, a sentence is factual if one can clearly state what the observations are that could confirm or disconfirm that sentence. After all, Carnap presupposes a specific criterion of meaning, namely the
Wittgenstein Ludwig Josef Johann Wittgenstein ( ; ; 26 April 1889 – 29 April 1951) was an Austrian philosopher who worked primarily in logic, the philosophy of mathematics, the philosophy of mind, and the philosophy of language. From 1929 to 1947, Witt ...
ian principle of verifiability. Indeed, he requires, as a precondition of meaningfulness, that all sentences be verifiable, which implies that a sentence is meaningful only if there is a way to verify if it is true or false. To verify a sentence, one needs to expound the empirical conditions and circumstances that would establish the truth of the sentence. As a result, it is clear for Carnap that metaphysical sentences are meaningless. They include concepts like "god", "soul", and "the absolute" that transcend experience and cannot be traced back or connected to direct observations. Because those sentences cannot be verified in any way, Carnap suggests that science, as well as philosophy, should neither consider nor contain them.


The logical analysis of language

At that point in his career, Carnap attempted to develop a full theory of the logical structure of scientific language. This theory, exposed in ''Logische Syntax der Sprache'' (1934; translated as ''The Logical Syntax of Language'', 1937) gives the foundations to his idea that scientific language has a specific formal structure and that its signs are governed by the rules of deductive logic. Moreover, the theory of logical syntax expounds a method with which one can talk about a language: it is a formal meta-theory about the pure forms of language. In the end, because Carnap argues that philosophy aims at the logical analysis of the language of science and thus is the logic of science, the theory of the logical syntax can be considered as a definite language and a conceptual framework for philosophy. The logical syntax of language is a formal theory. It is not concerned with the contextualized meaning or the truth-value of sentences. In contrast, it considers the general structure of a given language and explores the different structural relations that connect the elements of that language. Hence, by explaining the different operations that allow specific transformations within the language, the theory is a systematic exposition of the rules that operate within that language. In fact, the basic function of these rules is to provide the principles to safeguard coherence, to avoid contradictions, and to deduce justified conclusions. Carnap sees language as a calculus. This calculus is a systematic arrangement of symbols and relations. The symbols of the language are organized according to the class that they belong to—and it is through their combination that we can form sentences. The relations are different conditions under which a sentence can be said to follow, or to be the consequence, of another sentence. The definitions included in the calculus state the conditions under which a sentence can be considered of a certain type and how those sentences can be transformed. We can see the logical syntax as a method of formal transformation, i.e., a method for calculating and reasoning with symbols. Finally, Carnap introduces his well-known "principle of tolerance." This principle suggests that there is no moral in logic. When it comes to using a language, there is no good or bad, fundamentally true or false. In this perspective, the philosopher's task is not to bring authoritative interdicts prohibiting the use of certain concepts. In contrast, philosophers should seek general agreements over the relevance of certain logical devices. According to Carnap, those agreements are possible only through the detailed presentation of the meaning and use of the expressions of a language. In other words, Carnap believes that every logical language is correct only if this language is supported by exact definitions and not by philosophical presumptions. Carnap embraces a formal conventionalism. That implies that formal languages are constructed and that everyone is free to choose the language they find more suited to their purpose. There should not be any controversy over which language is the correct language; what matters is agreeing over which language best suits a particular purpose. Carnap explains that the choice of a language should be guided according to the security it provides against logical inconsistency. Furthermore, practical elements like simplicity and fruitfulness in certain tasks influence the choice of a language. Clearly enough, the principle of tolerance was a sophisticated device introduced by Carnap to dismiss any form of dogmatism in philosophy.


Inductive logic

After having considered problems in semantics, i.e. the theory of the concepts of meaning and truth (''Foundations of Logic and Mathematics'', 1939; ''Introduction to Semantics'', 1942; ''Formalization of Logic'', 1943), Carnap turned his attention to the subject of probability and
inductive logic Inductive reasoning refers to a variety of methods of reasoning in which the conclusion of an argument is supported not with deductive certainty, but with some degree of probability. Unlike ''deductive'' reasoning (such as mathematical inducti ...
. His views on that subject are, for the most part exposed in ''Logical foundations of probability'' (1950) where Carnap aims to give a sound logical interpretation of probability. Carnap thought that, according to certain conditions, the concept of probability had to be interpreted as a purely logical concept. In this view, probability is a basic concept anchored in all inductive inferences, whereby the conclusion of every inference that holds without deductive necessity is said to be more or less likely to be the case. In fact, Carnap claims that the problem of induction is a matter of finding a precise explanation of the logical relation that holds between a hypothesis and the evidence that supports it. An inductive logic is thus based on the idea that probability is a logical relation between two types of statements: the hypothesis (conclusion) and the premises (evidence). Accordingly, a theory of induction should explain how, by pure logical analysis, we can ascertain that certain evidence establishes a degree of confirmation strong enough to confirm a given hypothesis. Carnap was convinced that there was a logical as well as an empirical dimension in science. He believed that one had to isolate the experiential elements from the logical elements of a given body of knowledge. Hence, the empirical concept of frequency used in statistics to describe the general features of certain phenomena can be distinguished from the analytical concepts of probability logic that merely describe logical relations between sentences. For Carnap, the statistical and the logical concepts must be investigated separately. Having insisted on this distinction, Carnap defines two concepts of probability. The first one is logical and deals with the degree to which a given hypothesis is confirmed by a piece of evidence. It is the ''degree of confirmation''. The second is empirical and relates to the long-run rate of one observable feature of nature relative to another. It is the ''relative frequency.'' Statements belonging to the second concept are about reality and describe states of affairs. They are empirical and, therefore, must be based on experimental procedures and the observation of relevant facts. On the contrary, statements belonging to the first concept do not say anything about facts. Their meaning can be grasped solely with an analysis of the signs they contain. They are analytical sentences, i.e. true by virtue of their logical meaning. Even though these sentences could refer to states of affairs, their meaning is given by the symbols and relations they contain. In other words, the probability of a conclusion is given by the logical relation it has to the evidence. The evaluation of the degree of confirmation of a hypothesis is thus a problem of meaning analysis. Clearly, the probability of a statement about relative frequency can be unknown because it depends on the observation of certain phenomena, and one may not possess the information needed to establish the value of that probability. Consequently, the value of that statement can be confirmed only if it is corroborated by facts. In contrast, the probability of a statement about the degree of confirmation could be unknown, in the sense that one may miss the correct logical method to evaluate its exact value. But, such a statement can always receive a certain logical value, given the fact that this value only depends on the meaning of its symbols.


Primary source materials

The Rudolf Carnap Papers contain thousands of letters, notes and drafts, and diaries. The majority of his papers were purchased from his daughter, Hanna Carnap-Thost in 1974, by the University of Pittsburgh, with subsequent further accessions. Documents that contain financial, medical, and personal information are restricted. These were written over his entire life and career. Carnap used the mail regularly to discuss philosophical problems with hundreds of others. The most notable were: Herbert Feigl, Carl Gustav Hempel, Felix Kaufmann, Otto Neurath, and Moritz Schlick. Photographs are also part of the collection and were taken throughout his life. Family pictures and photographs of his peers and colleagues are also stored in the collection. Some of the correspondence is considered notable and consist of his student notes, his seminars with Frege (describing the ''
Begriffsschrift ''Begriffsschrift'' (German for, roughly, "concept-writing") is a book on logic by Gottlob Frege, published in 1879, and the formal system set out in that book. ''Begriffsschrift'' is usually translated as ''concept writing'' or ''concept notati ...
'' and the logic in mathematics). Carnap's notes from Russell's seminar in Chicago, and notes he took from discussions with Tarski, Heisenberg, Quine, Hempel, Gödel, and Jeffrey are also part of the University of Pittsburgh Library System's Archives and Special Collections. Digitized contents include: *Notes (old), 1958–1966 *More than 1,000 pages of lecture outlines are preserved that cover the courses that Carnap taught in the United States, Prague, and Vienna. Drafts of his published works and unpublished works are part of the collection. Additional Carnap materials can be found throughout th
Archives of Scientific Philosophy
at the University of Pittsburgh. *Manuscript drafts and typescripts both for his published works and for many unpublished papers and books. A partial listing include his first formulations of his ''Aufbau''. Much material is written in an older German shorthand, the Stolze-Schrey system. He employed this writing system extensively beginning in his student days. Some of the content has been digitized and is available through th
finding aid
The University of California also maintains a collection of Rudolf Carnap Papers. Microfilm copies of his papers are maintained by the Philosophical Archives at the University of Konstanz in Germany.


Selected publications

*1922.
Der Raum: Ein Beitrag zur Wissenschaftslehre
', '' Kant-Studien'', ''Ergänzungshefte''. 56 (his 1921
doctoral thesis 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: D ...
, published as a monograph supplement to the ''Kant-Studien'' journal). **''English translation:'
"Space: A Contribution to the Theory of Science"
(2005 draft), published version in: ''The Collected Works of Rudolf Carnap, Volume 1: Early Writings'' (2019) pp. 21–208 *1926.
Physikalische Begriffsbildung
'. Karlsruhe: Braun. **''English translation''
"Physical Concept Formation"
(1992 draft), published version in: ''Collected Works'' (2019) pp. 339–440 *1928. '' Scheinprobleme in der Philosophie'' (''Pseudoproblems in Philosophy''). Berlin: Weltkreis-Verlag. *1928. ''Der Logische Aufbau der Welt'' (his
habilitation thesis Habilitation is the highest university degree, or the procedure by which it is achieved, in Germany, France, Italy, Poland and some other European and non-English-speaking countries. The candidate fulfills a university's set criteria of excellen ...
). Leipzig: Felix Meiner Verlag. **''English translation:'' Rolf A. George, 1967. '' The Logical Structure of the World. Pseudoproblems in Philosophy''. University of California Press. *1929. '' Abriss der Logistik, mit besonderer Berücksichtigung der Relationstheorie und ihrer Anwendungen''. **(''Revised) English translation: Introduction to Symbolic Logic'' (1958) *1931. **''English translation: "'' The Elimination of Metaphysics Through Logical Analysis of Language" Pap, Arthur (trans.) in: Ayer, A.J (ed.) ''
Logical Positivism Logical positivism, also known as logical empiricism or neo-positivism, was a philosophical movement, in the empiricist tradition, that sought to formulate a scientific philosophy in which philosophical discourse would be, in the perception of ...
'' (1965) pp. 60–81 *1934. ''Logische Syntax der Sprache''. **''English translation:'' 1937, '' The Logical Syntax of Language''. Kegan Paul. *1935.
Philosophy and Logical Syntax
'. Bristol UK: Thoemmes

*1939, '' Foundations of Logic and Mathematics'' in ''International Encyclopedia of Unified Science,'' Vol. I, No. 3. University of Chicago Press. *1942. '' Introduction to Semantics''. Harvard Uni. Press. *1943. ''Formalization of Logic''. Harvard Uni. Press. *1945
"On Inductive Logic"
in ''Philosophy of Science'', Vol. 12, pp. 72–97. *1945.
The Two Concepts of Probability"
'' Philosophy and Phenomenological Research'', Vol. 5, No. 4, pp.513–532. *1947
"On the Application of Inductive Logic"
in '' Philosophy and Phenomenological Research'', Vol. 8, pp.133–148. *1947.
Meaning and Necessity: a Study in Semantics and Modal Logic
'. University of Chicago Press. nlarged edition published in 1956*1950, (1962 2nd ed:) '' Logical Foundations of Probability''. University of Chicago Press
pp. 3–15
*1950.

, ''Revue Internationale de Philosophie'' 4: 20–40. reprinted in:
Paul Benacerraf Paul Joseph Salomon Benacerraf (; 26 March 1930 – 13 January 2025) was a French-born American philosopher working in the field of the philosophy of mathematics who taught at Princeton University his entire career, from 1960 until his retirement ...
&
Hilary Putnam Hilary Whitehall Putnam (; July 31, 1926 – March 13, 2016) was an American philosopher, mathematician, computer scientist, and figure in analytic philosophy in the second half of the 20th century. He contributed to the studies of philosophy of ...
(eds.), ''Philosophy of Mathematics: Selected Readings'' (1964) *1952.
The Continuum of Inductive Methods
'. University of Chicago Press. *1958. '' Introduction to Symbolic Logic and its Applications''. trans. W. H. Myer and J. Wilkinson, Dover publications, New York. Abriss der Logistik'' (1929)] *1962. "The Aim of Inductive Logic" in (eds.) Ernest Nagel, Nagel, Suppes, and Tarski, '' Logic, Methodology and Philosophy of Science'' Stanford,, pp 303–318 (revised and expanded in Carnap & Jeffrey 1971). *1963, "Intellectual Autobiography" in Schilpp. Paul A. (ed.) '' The Philosophy of Rudolf Carnap,''
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 (2001–20 ...
V. XI, Open Court p. 3–83 (1963) *1964. "The Logicist Foundations of Mathematics" in
Paul Benacerraf Paul Joseph Salomon Benacerraf (; 26 March 1930 – 13 January 2025) was a French-born American philosopher working in the field of the philosophy of mathematics who taught at Princeton University his entire career, from 1960 until his retirement ...
&
Hilary Putnam Hilary Whitehall Putnam (; July 31, 1926 – March 13, 2016) was an American philosopher, mathematician, computer scientist, and figure in analytic philosophy in the second half of the 20th century. He contributed to the studies of philosophy of ...
(eds.), '' Philosophy of Mathematics: Selected Readings''. Englewood Cliffs, NJ, USA: Cambridge University Press. pp. 41--52 *1966. ''An Introduction to the Philosophy of Science''. Basic Books. *1966. '' Philosophical Foundations of Physics''.
Martin Gardner Martin Gardner (October 21, 1914May 22, 2010) was an American popular mathematics and popular science writer with interests also encompassing magic, scientific skepticism, micromagic, philosophy, religion, and literatureespecially the writin ...
, ed. Basic Books
Online excerpt.
*1971. ''Studies in Inductive Logic and Probability, Vol. 1''. with Jeffrey, R. C, University of California Press. *197
"Notes on probability and induction"
''Synthese'' 25 (3-4):269 - 298, reprinted with slight revision in Hintikka (1975) *1975 “Observation Language and Theoretical Language”, in
Jaakko Hintikka Kaarlo Jaakko Juhani Hintikka (; ; 12 January 1929 – 12 August 2015) was a Finnish philosopher and logician. Hintikka is regarded as the founder of formal epistemic logic and of game semantics for logic. Life and career Hintikka was born in ...
(ed.), '' Rudolf Carnap, logical empiricist: materials and perspectives''. Boston: D. Reidel Pub. Co.. pp. 75--85 [translation o
“Beobachtungssprache und Theoretische Sprache”
''Dialectica'', 12(3–4): 236–248 1958] *1977. ''Two Essays on Entropy''. Abner Shimony, Shimony, Abner, ed. University of California Press. * 1980. "A Basic System of Inductive Logic Part II" in: Richard Jeffrey, Jeffrey, R. C. (ed.) ''Studies in Inductive Logic and Probability, Vol. 2''. . University of California Press. * 2000. ''Untersuchungen zur Allgemeinen Axiomatik''. Edited from unpublished manuscript by T. Bonk and J. Mosterín. Darmstadt: Wissenschaftliche Buchgesellschaft. 167  .. * 2017
“Value Concepts (1958)”
''Synthese'', 194(1): 185–194. * 2019. ''Rudolf Carnap: Early Writings'', A.W. Carus, Michael Friedman, Wolfgang Kienzler, Alan Richardson, and Sven Schlotter (eds.), (The Collected Works of Rudolf Carnap, 1), New York: Oxford University Press. *For a more complete listing see Carnap’s Works in "Linked bibliography''".''


Filmography

* ''Interview with Rudolf Carnap'', German TV, 1964Online version in three parts
123


See also

*
Definitions of philosophy Definitions of philosophy aim at determining what all forms of philosophy have in common and how to distinguish philosophy from other disciplines. Many different definitions have been proposed but there is very little agreement on which is the rig ...
* Second Conference on the Epistemology of the Exact Sciences * Second Davos Hochschulkurs


References


Sources

* * *
Ivor Grattan-Guinness Ivor Owen Grattan-Guinness (23 June 1941 – 12 December 2014) was a historian of mathematics and logic. Life Grattan-Guinness was born in Bakewell, England; his father was a mathematics teacher and educational administrator. He gained his ...
, 2000. ''In Search of Mathematical Roots''. Princeton Uni. Press. * Thomas Mormann, 2000. ''Rudolf Carnap''. C. H. Beck. *
Willard Quine Willard Van Orman Quine ( ; known to his friends as "Van"; June 25, 1908 – December 25, 2000) was an American philosopher and logician in the analytic tradition, recognized as "one of the most influential philosophers of the twentieth centur ...
**1951, "
Two Dogmas of Empiricism "Two Dogmas of Empiricism" is a canonical essay by analytic philosopher Willard Van Orman Quine published in 1951. According to University of Sydney professor of philosophy Peter Godfrey-Smith, this "paper ssometimes regarded as the most impor ...
." ''The Philosophical Review'' 60: 20–43. Reprinted in his 1953 ''From a Logical Point of View''. Harvard University Press. **1985, ''The Time of My Life: An Autobiography''. MIT Press. *Richardson, Alan W., 1998. ''Carnap's construction of the world: the ''Aufbau'' and the emergence of logical empiricism''. Cambridge Uni. Press. *Schilpp, P. A., ed., 1963. '' The Philosophy of Rudolf Carnap''. LaSalle IL: Open Court. *Spohn, Wolfgang, ed., 1991. ''Erkenntnis Orientated: A Centennial Volume for Rudolf Carnap and Hans Reichenbach''. Kluwer Academic Publishers. *1991. ''Logic, Language, and the Structure of Scientific Theories: Proceedings of the Carnap-Reichenbach Centennial, University of Konstanz, May 21–24, 1991''. University of Pittsburgh Press. *Wagner, Pierre, ed., 2009. ''Carnap's Logical Syntax of Language''. Palgrave Macmillan. *Wagner, Pierre, ed., 2012. ''Carnap's Ideal of Explication and Naturalism''. Palgrave Macmillan.


Further reading

* Sarkar, Sahotrabr>"Rudolf Carnap (1891–1970)"
in Martinich, A. P.; Sosa, David (eds.) ''A Companion to Analytic Philosophy'', Blackwell, (2001'')'' * 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 ''The New York Review of Books'' (or ''NYREV'' or ''NYRB'') is a semi-monthly magazine with articles on literature, culture, economics, science and current affairs. Published in New York City, it is inspired by the idea that the discussion of ...
'', vol. LXIV, no. 20 (21 December 2017), pp. 74–76. * Psillos, Stathis
"Rudolf Carnap's 'Theoretical Concepts in Science'"
''Studies in History and Philosophy of Science Part A'' 31(1) (2000):151–172.


External links

* * *
Rudolf Carnap Webpage and Directory of Internet Resources
* Homepage of th
Collected Works of Rudolf Carnap
– Department of Philosophy,
Carnegie Mellon University Carnegie Mellon University (CMU) is a private research university in Pittsburgh, Pennsylvania, United States. The institution was established in 1900 by Andrew Carnegie as the Carnegie Technical Schools. In 1912, it became the Carnegie Institu ...

Precis
of Carnap's philosophy

Philosophy at RBJones.com * R. Carnap
"Von der Erkenntnistheorie zur Wissenschaftslogik"
''Paris Congress in 1935'', Paris, 1936. * R. Carnap
"Über die Einheitssprache der Wissenschaft"
''Paris Congress in 1935'', Paris, 1936. * R. Carnap
"Wahrheit und Bewährung"
''Paris Congress in 1935'', Paris, 1936.
Rudolf Carnap Papers:
(Rudolf Carnap Papers, 1905–1970, ASP.1974.01, Special Collections Department,
University of Pittsburgh The University of Pittsburgh (Pitt) is a Commonwealth System of Higher Education, state-related research university in Pittsburgh, Pennsylvania, United States. The university is composed of seventeen undergraduate and graduate schools and colle ...
.)
Das Fremdpsychische bei Rudolf Carnap
(German) by Robert Bauer.
FBI file on Rudolph Carnap
*

obituary in ''
The New York Times ''The New York Times'' (''NYT'') is an American daily newspaper based in New York City. ''The New York Times'' covers domestic, national, and international news, and publishes opinion pieces, investigative reports, and reviews. As one of ...
'', 15 September 1970
''Homage to Rudolf Carnap'' (1970)
by Feigl, Hempel, Jeffrey, Quine ''et al''. reprinted in frontmatter of ''RUDOLF CARNAP, LOGICAL EMPIRICIST'' (1975) * udioCarnap lecturing on 'Theoretical Concepts in Science' at the meeting of the
American Philosophical Association The American Philosophical Association (APA) is the main professional organization for philosophers in the United States. Founded in 1900, its mission is to promote the exchange of ideas among philosophers, to encourage creative and scholarl ...
, Pacific Division, at Santa Barbara, California, on 29 December 1959. {{DEFAULTSORT:Carnap, Rudolf 1891 births 1970 deaths 20th-century American male writers 20th-century American philosophers 20th-century atheists 20th-century American essayists 20th-century German male writers 20th-century German non-fiction writers 20th-century German philosophers American atheists American Esperantists American logicians American male essayists American male non-fiction writers American people of German descent American socialists Analytic philosophers Atheist philosophers Corresponding fellows of the British Academy Empiricists Epistemologists German atheists Emigrants from Nazi Germany to the United States German Esperantists German essayists German expatriates in Austria German logicians German male non-fiction writers German socialists Harvard University people Institute for Advanced Study visiting scholars American lecturers German lecturers Ontologists People from the Rhine Province Philosophers of language Philosophers of logic Philosophers of mathematics Philosophers of probability Philosophers of science Philosophers of time Philosophy academics UCLA Department of Philosophy faculty University of California, Los Angeles faculty University of Chicago faculty University of Jena alumni University of Vienna alumni Academic staff of the University of Vienna Vienna Circle Writers from Wuppertal