The Life of Rudolf Carnap


based on his intellectual autobiography in [Carnap63]


Rudolf Carnap was a leading member of the Vienna Circle and proponent of the philosophy of Logical Positivism. In 1936 he emigrated to the USA and continued to develop his brand of formally oriented philosophical analysis.
Student Years
Carnap heads for the Philosophy of Science under the influence of Kant and Frege.
Germany (1919-1926)
After a dissertation on the Philosophical Foundations of Geometry Carnap begins his work on what was later to be called logical positivism.
Vienna (1926-1935)
In 1926 Carnap took a position at the University of Vienna, permitting him to become a member of the Vienna Circle.
USA (1936-1970)
In 1936 Carnap goes to Chicago and spends the rest of his life in the USA, becoming a citizen in 1941.

Student Years:

Carnap heads for the Philosophy of Science under the influence of Kant and Frege.
Born in 1891 in Northwest Germany, Carnap was fascinated, watching his mother working on a book on her father's life, by "the magical activity of putting thought onto paper". In 1910 they moved to Jena where he studied at the Universities of Jena and Frieberg/i.B.
Interests and Inspiration
As a student Carnap was interested first mainly in mathematics and philosophy, later in philosophy and physics. He liked the decisiveness of mathematical demonstration by comparison with the endless controversies of philosophy, but his "most fruitful inspiration" came from the lectures of Frege on symbolic logic. He preferred physics to the other empirical sciences because of its ability to make exact numerical predictions.
Kant's Critique
As a student Carnap seems to have been influenced by detailed study of Kant's Critique of Pure Reason, particular by Kant's writings on the geometry of space. His dissertation was to be in this area.
Gottlob Frege
Carnap attended lecture courses given by Frege, two on his Begriffschrift and one on Logik in der Mathematik, though the philosophical signficance of Frege's work was not made clear.
Religion and Morality
During this period Carnap gradually came to disbelieve in God, without being aware of any change in his beliefs on moral questions.
The Great War: socialism, relativity
This period of Carnap's life ends with a period of military conscription during the first world war. During this period he nevertheless found some time for his scientific and philosophical interests, and became interested in socialism and in Einstein's theory of relativity.


After a dissertation on the Philosophical Foundations of Geometry Carnap begins his work on what was later to be called logical positivism.
After the war Carnap returned to his studies. He decided to work in philosophy and theoretical physics, dropping experimental physics, and completed his doctoral dissertation on the philosophical foundations of geometry.
He then continued his work in logic and philosophy under the inspiration of Frege and Russell, working on early versions of his books Abriss der Logistik a logic text based on Principia Mathematica and Der Logische Aufbau der Welt, The Logical Structure of the World.
"The men who had the strongest influence on my philosophical thinking were Frege and Russell."
Frege had the strongest influence on Carnap in the fields of logic and semantics. Carnap studied Die Grundgesetze der Arithmetic in 1920. From Frege he learned carefulness and clarity in the analysis of concepts and expressions, the distinction between syntax and semantics, and between sense and denotation. He also learned that knowledge in mathematics has essentially the same nature as knowledge in logic (which view was later to be made more "radical and precise" chiefly through the influence of Wittgenstein).
In general philosophical thinking Carnap learned most from Bertrand Russell. In 1921 he read Our knowledge of the external world. This made "an especially vivid impression" on him because it formulated clearly a view (on the logico-analytic method of philosophy) which Carnap already implicitly held. He quotes an appeal by Russellquote which he felt "had been directed to me personally". Carnap then undertook intensive study of Russell's books on the theory of knowledge and the methodology of science.
Der Logische Aufbau der Welt
The largest part of the period from 1922-5 was devoted to a first version of
"The logical structure of the world".
analytic method
This work began with attempts to analyse concepts from ordinary language, with the intention of ultimately defining these concepts in terms of sensory phenomena (a color at a position in the visual field). This was guided by psychological facts but intended only as a "rational reconstruction" giving the same results. The logic of relations in Principia Mathematica was considered by Carnap a suitable tool for this kind of task. The influence of Gestalt psychology later caused a shift to a basis in the elements of experience rather than in sense-data.
phenomenal v. physical
Though the concepts in Aufbau were constructed on a phenomenalistic basis (influenced by "some radical empiricist or positivist german philosophers of the end of the 19th century") Carnap also indicated the possibility of using a physicalistic basis
principle of tolerance
In discussing these ideas, both with friends and in the book, Carnap found himself moving with ease between different kinds of language, e.g. realistic, idealistic, nominalistic. Only later did he recognise clearly that his way of thinking was neutral with respect to the "traditional controversies", realism/idealism, nominalism/platonism, materialism/spiritualism This neutral attitude remained with Carnap throughout his life and was formulated by his principle of tolerance in Logical Syntax [Carnap34].
A first version of Der Logische Aufbau der Welt was complete in 1925, but was revised again before publication in 1928 [Carnap28]. Carnap never returned to the program envisaged by the book, partly because he came later to prefer a physicalistic rather than phenomenalistic basis.


In 1926 Carnap took a position at the University of Vienna and joined the Vienna Circle.
"For my philosophical work the period in Vienna was one of the most stimulating, enjoyable, and fruitful periods of my life."
Much of the stimulus came from discussions with other philosophers.
The Vienna Circle
A forum for open discussion on the philosophical foundations of science, birthplace of logical positivism. Here the typescript of Der Logische Aufbau was read and discussed. Participants included Schlick, Mach, Boltzmann, Neurath, Waismannn, and Gödel.
A large part of The Tractactus was real aloud and discussed sentence by sentence by the circle, and exerted a strong influence. From summer 1927 meetings began between Schilck, Waismann and Carnap. Though Carnap was excluded from the beginning of 1929, he was still exposed to the continuing development of Wittgenstein's view through the systematic expositions which he attempted for the circle.
Morris and Quine
In 1934 Morris and Quine visited Vienna and also met Carnap in Prague. They later helped to make Logical Positivism known in America and assisted Carnap in moving to America.
The Warsaw Group
First contact with the philosophers at Warsaw came when Tarski was invited to Vienna in February 1930 and lectured on metamathematics, which introduced Carnap to the use of formal metalanguages. Discussions with Tarski and with Gödel helped Carnap towards his theory of logical syntax. He disagreed with Tarski on the analytic/synthetic dichotomy, which Tarski thought a matter of degree. Carnap visited Warsaw in November 1930, giving lectures to the Warsaw Philosophical Society, talking privately to Tarski, Lesniewski and Kortarbinski, who were all involved in work on semantics.
At this time Popper was also in Vienna, but was not a member of the circle. Carnap read the manuscript of Logik der Forschung and had discussions with Popper in the summer of 1932. Though Popper had "similar" attitudes to the circle, Carnap felt that he overemphasised the differences. Popper criticised "the positivists" and antagonised some of the members of the circle.
Some Publications
In his intellectual autobiography Carnap says little about his publications during this period.
Nevertheless, there were plenty, of which the following are a sample.
1928 Der Logische Aufbau der Welt - The Logical Structure of the World - see above. [Carnap28]
1929 Abriss der Logistik - An Introduction to Logic giving special attention to the theory of relations and its applications. [Carnap29]
1932 The Unity of Science - physicalistic language as a universal language for science. [Carnap32]
1934 The Logical Syntax of Language - a purely analytic study of the structure of linguistic expressions. [Carnap34]
1935 Philosophy and Logical Syntax - the text of three lectures given in London in 1934 describing Carnap's Syntactical MethodNotes. [Carnap35]


In 1936 Carnap goes to Chicago and spends the rest of his life in the USA, becoming a citizen in 1941.
Philosophy in the USA
Some observations by Carnap
Good for Logic
Carnap observes that the state of Logic teaching in the USA was much better than in Europe, so the USA was much more fertile ground than Europe for developing scientific philosophy.
Not Enough Logic
But still he found that an insufficient understanding of symbolic logic was an impediment in methodological discussions.
Opposition by Tarski and Quine
And in this mecca of logical knowledge he finds himself at odds with both Tarski and Quine on whether there is a clean distinction between analytic and synthetic judgements or whether this is "just a matter of degree".
Scholasticism Lives on in Chicago
He mentions the very thorough standards of historical research at Chicago, but is dismayed at the acceptance in historical contexts of arguments which modern logic has shown to be fallacious.
"I had the weird feeling that I was sitting among a group of medieval learned men with long beards and solemn robes. [...] I would perhaps dream that one of my colleagues raised the famous question of how many angels could dance on the point of a needle."
Chronology (from 1936)
1936 visits USA for Harvard terncentenary celebration
1936-52 Chicago - teaches winter quarter 1936 and then obtains permanent position
1937-8 research seminar with Hempel and Helner
1939 Russell @ Chicago lecturing on meaning and truth
1941 becomes citizen of USA
1940-41 takes visiting professorship at Harvard where Russell was giving the William James lectures. Participates in Logic group with Russell, Quine, Tarski, Goodman and others. Goodman provides detailed feedback on the Aufbau and later produces his own The Structure of Appearances
1952-4 Institute of Advanced Studies Princeton. Worked with Kemeny on inductive logic. Talks with Von Neumann and Pauli on theoretical physics. Also with Einstein.
Some Publications
1939 Foundations of Logic and Mathematics (International Encyclopaedia of Unified Science, Vol.I No.3) [Carnap39]
1942 Introduction to Semantics first of a series of studies in semantics [Carnap42]
1943 Formalisation of Logic [Carnap43]
1947 Meaning and Necessity - a Study in Semantics and Modal Logic. [Carnap47]
1958 Introduction to Symbolic Logic and Its Applications - translation by Meyer and Wilkinson of Einführung in die symbolische Logik. [Carnap54]
1958 An Introduction to the Philosophy of Science - an approved transcription of Carnap's celebrated lectures at the U. of California (L.A.) in 1958. [Carnap58]
1935 The Philosophy of Rudolf Carnap - Library of Living Philosophers. [Carnap63]

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