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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 and an advocate of logical positivism. He is considered "one of the giants among twentieth-century philosophers."


Biography

Carnap's father had risen 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 scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, architecture, biofacts or ecofacts, sites, and cultural landsca ...
Wilhelm Dörpfeld. 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 Christian denomination, branch of Christianity that follows the theological tenets of the Reformation, Protestant Reformation, a movement that began seeking to reform the Catholic Church from within in the 16th century agai ...
family, but later became an atheist. He began his formal education at the Barmen Gymnasium and the Gymnasium in
Jena Jena () is a German city 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 inhabitants, while the city itself has a po ...
. From 1910 to 1914, he attended the
University of Jena The University of Jena, officially the Friedrich Schiller University Jena (german: Friedrich-Schiller-Universität Jena, abbreviated FSU, shortened form ''Uni Jena''), is a public research university located in Jena, Thuringia, Germany. The ...
, intending to write a thesis in
physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which ...
. He also intently studied
Immanuel Kant Immanuel 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, ethics, and ...
's '' Critique of Pure Reason'' during a course taught by Bruno Bauch, and was one of 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 p ...
's courses in
mathematical logic Mathematical logic is the study of formal logic within mathematics. Major subareas include model theory, proof theory, set theory, and recursion theory. Research in mathematical logic commonly addresses the mathematical properties of forma ...
. During his university years he became enthralled with the
German Youth Movement The German Youth Movement (german: Die deutsche Jugendbewegung) 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 ...
. While Carnap held moral and political opposition to
World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...
, 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 Humboldt-Universität zu Berlin (german: Humboldt-Universität zu Berlin, abbreviated HU Berlin) is a German public research university in the central borough of Mitte in Berlin. It was established by Frederick William III on the initiative ...
, 1917–18, where
Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theor ...
was a newly appointed professor. Carnap then attended the
University of Jena The University of Jena, officially the Friedrich Schiller University Jena (german: Friedrich-Schiller-Universität Jena, abbreviated FSU, shortened form ''Uni Jena''), is a public research university located in Jena, Thuringia, Germany. The ...
, where he wrote a thesis defining an axiomatic theory of
space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually consi ...
and
time Time is the continued sequence of existence and event (philosophy), events that occurs in an apparently irreversible process, irreversible succession from the past, through the present, into the future. It is a component quantity of various me ...
. 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 Kantian style, and published as ''Der Raum'' (''Space'') in a supplemental issue of ''
Kant-Studien ''Kant-Studien'' ("Kant Studies") is a quarterly journal of philosophy, focusing on Immanuel Kant. The journal was established in 1897. It publishes articles in English and German. See also * List of philosophy journals This is a list of academic ...
'' (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 mathematician, philosopher, logician, and public intellectual. He had a considerable influence on mathematics, logic, set theory, linguistics, a ...
's work on logic and philosophy, which put a sense of the aims 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'' 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 , 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 ...
, the founder of
phenomenology Phenomenology may refer to: Art * Phenomenology (architecture), based on the experience of building materials and their sensory properties Philosophy * Phenomenology (philosophy), a branch of philosophy which studies subjective experiences and a ...
, and continued to write on physics from a logical positivist perspective. Carnap discovered a kindred spirit when he met Hans Reichenbach at a 1923 conference. Reichenbach introduced Carnap to Moritz Schlick, a professor at the
University of Vienna The University of Vienna (german: Universität Wien) is a public research university located in Vienna, Austria. It was founded by Duke Rudolph IV in 1365 and is the oldest university in the German-speaking world. With its long and rich hi ...
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, directed largely by Schlick and including Hans Hahn, Friedrich Waismann, Otto Neurath, and Herbert Feigl, with occasional visits by Hahn's student Kurt Gödel. When Wittgenstein visited Vienna, Carnap would meet with him. He (with Hahn and Neurath) wrote the 1929 manifesto of the Circle, and (with Hans Reichenbach) initiated the philosophy journal '' Erkenntnis''. In February 1930 Alfred Tarski lectured in Vienna, and during November 1930 Carnap visited Warsaw. On these occasions he learned much about Tarski's
model theoretic In mathematical logic, model theory is the study of the relationship between formal theories (a collection of sentences in a formal language expressing statements about a mathematical structure), and their models (those structures in which the st ...
method of
semantics Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference, meaning, or truth. The term can be used to refer to subfields of several distinct disciplines, including philosophy, linguistics and comput ...
.
Rose Rand Rose Rand (June 14, 1903 – July 28, 1980) was an Austrian-American logician and philosopher. She was a member of the Vienna Circle. Life and work Rose (Rozalia) Rand was born in Lemberg in the Austrian crown land of Galicia (today ...
, 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 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 a left-wing economic philosophy and movement encompassing a range of economic systems characterized by the dominance of social ownership of the means of production as opposed to private ownership. As a term, it describes the ...
and pacifist beliefs put him at risk in
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 ...
, emigrated to the United States in 1935 and became a naturalized citizen 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, U of C, or UChi) is a private research university in Chicago, Illinois. Its main campus is located in Chicago's Hyde Park neighborhood. The University of Chicago is consistently ranked among the b ...
. 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 empiricism, a 20th-century movement in the philosophy of science. He is e ...
, 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 Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of highe ...
, 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 McKe ...
, Charles Hartshorne, and Manley Thompson.) Carnap's years at Chicago were nonetheless very productive ones. He wrote books on
semantics Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference, meaning, or truth. The term can be used to refer to subfields of several distinct disciplines, including philosophy, linguistics and comput ...
(Carnap 1942, 1943, 1956),
modal logic Modal logic is a collection of formal systems developed to represent statements about necessity and possibility. It plays a major role in philosophy of language, epistemology, metaphysics, and natural language semantics. Modal logics extend ot ...
, and on the philosophical foundations of
probability Probability is the branch of mathematics concerning numerical descriptions of how likely an event is to occur, or how likely it is that a proposition is true. The probability of an event is a number between 0 and 1, where, roughly speaking, ...
and
inductive logic Inductive reasoning is a method of reasoning in which a general principle is derived from a body of observations. It consists of making broad generalizations based on specific observations. Inductive reasoning is distinct from ''deductive'' rea ...
(Carnap 1950, 1952). After a stint at the
Institute for Advanced Study The Institute for Advanced Study (IAS), located in Princeton, New Jersey, in the United States, is an independent center for theoretical research and intellectual inquiry. It has served as the academic home of internationally preeminent schola ...
in
Princeton Princeton University is a private research university in Princeton, New Jersey. Founded in 1746 in Elizabeth as the College of New Jersey, Princeton is the fourth-oldest institution of higher education in the United States and one of the nin ...
(1952–1954), he joined the UCLA Department of Philosophy in 1954, Hans Reichenbach 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 land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant un ...
, because accepting that position required that he sign a loyalty oath, a practice to which he was opposed on principle. While at UCLA, he wrote on scientific knowledge, the analytic–synthetic distinction, and the
verification principle Verificationism, also known as the verification principle or the verifiability criterion of meaning, is the philosophical doctrine which maintains that only statements that are empirically verifiable (i.e. verifiable through the senses) are cogniti ...
. His writings on
thermodynamics Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws ...
and on the foundations of probability and
inductive logic Inductive reasoning is a method of reasoning in which a general principle is derived from a body of observations. It consists of making broad generalizations based on specific observations. Inductive reasoning is distinct from ''deductive'' rea ...
, were published posthumously as Carnap (1971, 1977, 1980). Carnap taught himself Esperanto when he was 14 years of age, and remained sympathetic to it (Carnap 1963). He later attended the
World Congress of Esperanto The World Esperanto Congress ( eo, Universala Kongreso de Esperanto, UK) is an annual Esperanto convention. It has the longest tradition among international Esperanto conventions, with an almost unbroken run for 113 years. The congresses have be ...
in 1908 and 1922, and employed the language while traveling. 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 (; ), or the theory of knowledge, is the branch of philosophy concerned with knowledge. Epistemology is considered a major subfield of philosophy, along with other major subfields such as ethics, logic, and metaphysics. Epi ...
and philosophy of logic.


''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,
natural sciences Natural 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 review and repeat ...
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 thesis at the
University of Vienna The University of Vienna (german: Universität Wien) is a public research university located in Vienna, Austria. It was founded by Duke Rudolph IV in 1365 and is the oldest university in the German-speaking world. With its long and rich hi ...
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 Mathematical logic is the study of formal logic within mathematics. Major subareas include model theory, proof theory, set theory, and recursion theory. Research in mathematical logic commonly addresses the mathematical properties of formal ...
, 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 studies the fundamental nature of reality, the first principles of being, identity and change, space and time, causality, necessity, and possibility. It includes questions about the nature of conscio ...
, 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 which, 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 Mathematical logic is the study of formal logic within mathematics. Major subareas include model theory, proof theory, set theory, and recursion theory. Research in mathematical logic commonly addresses the mathematical properties of formal ...
, 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, theses 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 are the observations that could confirm or disconfirm that sentence. After all, Carnap presupposes a specific criterion of meaning, namely the Wittgensteinian 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 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. It is in the ''logical syntax'' that Carnap introduces his notable 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 it finds more suited to his 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 is a method of reasoning in which a general principle is derived from a body of observations. It consists of making broad generalizations based on specific observations. Inductive reasoning is distinct from ''deductive'' rea ...
. 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 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 concepts 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, 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 with 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 Carnap Papers consist of approximately 10,000 personal letters of correspondence. The papers were donated by his daughter, Hanna Carnap-Thost in 1974. 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-script") 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 nota ...
'' 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 part of the University of Pittsburgh's Archives and 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. *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. Much of the content has been digitized. 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 ''Kant-Studien'' ("Kant Studies") is a quarterly journal of philosophy, focusing on Immanuel Kant. The journal was established in 1897. It publishes articles in English and German. See also * List of philosophy journals This is a list of academic ...
'', Ergänzungshefte, no. 56 ( doctoral thesis). *1926. ''Physikalische Begriffsbildung''. Karlsruhe: Braun. *1928. '' Scheinprobleme in der Philosophie'' (''Pseudoproblems in Philosophy''). Berlin: Weltkreis-Verlag. *1928. ''Der Logische Aufbau der Welt'' (his habilitation thesis). Leipzig: Felix Meiner Verlag. English translation by 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''. Springer. *1931. — ''English translation:'' *1934. ''Logische Syntax der Sprache''. English translation 1937, '' The Logical Syntax of Language''. Kegan Paul. *1996 (1935). ''Philosophy and Logical Syntax''. Bristol UK: Thoemmes
Excerpt.
*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'' in ''Philosophy and Phenomenological Research'', Vol. 5, No. 4, pp. 513–532. *1947. "On the Application of Inductive Logic" in ''
Philosophy and Phenomenological Research ''Philosophy and Phenomenological Research'' (''PPR'') is a bimonthly philosophy journal founded in 1940. Until 1980, it was edited by Marvin Farber, then by Roderick Chisholm and since 1986 by Ernest Sosa. It considers itself open to a variety ...
'', Vol. 8, pp. 133–148. *1956 (1947).
Meaning and Necessity: a Study in Semantics and Modal Logic
'. University of Chicago Press. *1950. '' Logical Foundations of Probability''. University of Chicago Press
pp. 3–15
*1950.

, ''Revue Internationale de Philosophie'' 4: 20–40. *1952. ''The Continuum of Inductive Methods''. University of Chicago Press. *1958. '' Introduction to Symbolic Logic and its Applications''. Dover publications, New York. *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 (2001–2013 ...
V. XI,
Open Court Open or OPEN may refer to: Music * Open (band), Australian pop/rock band * The Open (band), English indie rock band * ''Open'' (Blues Image album), 1969 * ''Open'' (Gotthard album), 1999 * ''Open'' (Cowboy Junkies album), 2001 * ''Open'' (YF ...
p. 3–83 (1963) *1966. ''An Introduction to the Philosophy of Science''. Basic Books. *1966. '' Philosophical Foundations of Physics''. Martin Gardner, ed. Basic Books
Online excerpt.
*1971. '' Studies in Inductive Logic and Probability, Vol. 1''. University of California Press. *1977. '' Two Essays on Entropy''. Shimony, Abner, ed. University of California Press. *1980. ''Studies in Inductive Logic and Probability, Vol. 2''. Jeffrey, R. C., ed. University of California Press. *2000. ''Untersuchungen zur Allgemeinen Axiomatik''. Edited from unpublished manuscript by T. Bonk and J. Mosterín. Darmstadt: Wissenschaftliche Buchgesellschaft. 167 pp. .
Online bibliography
is under construction and has no entries dated later than 1937.


Filmography

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


See also

* Definitions of philosophy * 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 b ...
, 2000. ''In Search of Mathematical Roots''. Princeton Uni. Press. *
Thomas Mormann Thomas Mormann (born 1951) is Professor of Philosophy at the University of the Basque Country in Donostia-San Sebastian, Spain. He obtained his PhD in Mathematics from the University of Dortmund (1978). He obtained his Habilitation from the Univ ...
, 2000. ''Rudolf Carnap''. C. H. Beck. * Willard Quine **1951, '' Two Dogmas of Empiricism''. ''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

* Holt, Jim
"Positive Thinking"
(review of
Karl Sigmund Karl Sigmund (born July 26, 1945) is a Professor of Mathematics at the University of Vienna and one of the pioneers of evolutionary game theory. Career Sigmund was schooled in the Lycée Francais de Vienne. From 1963 to 1968 he studied at the In ...
, ''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 i ...
'', 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
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 public state-related research university in Pittsburgh, Pennsylvania. The university is composed of 17 undergraduate and graduate schools and colleges at its urban Pittsburgh campus, home to the univers ...
.)
Das Fremdpsychische bei Rudolf Carnap
(German) by Robert Bauer.
FBI file on Rudolph Carnap
*

obituary in ''
The New York Times ''The New York Times'' (''the Times'', ''NYT'', or the Gray Lady) is a daily newspaper based in New York City with a worldwide readership reported in 2020 to comprise a declining 840,000 paid print subscribers, and a growing 6 million paid ...
'', 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, 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 non-fiction writers 20th-century American philosophers 20th-century atheists 20th-century 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 German emigrants to the United States German Esperantists German essayists German expatriates in Austria German logicians German male non-fiction writers German philosophers German socialists Harvard University people Institute for Advanced Study visiting scholars Lecturers Ontologists People from the Rhine Province Philosophers of language Philosophers of logic Philosophers of mathematics Philosophers of science Philosophers of time Philosophy academics Philosophy writers UCLA Philosophy University of California, Los Angeles faculty University of Chicago faculty University of Jena alumni University of Vienna alumni Academics of the University of Vienna Vienna Circle Writers from Wuppertal