See studies by P. A. Schilpp, ed. (1963, repr. 1984) and R. Butrick (1970).
(born May 18, 1891, Ronsdorf, Ger.—died Sept. 14, 1970, Santa Monica, Calif., U.S.) German-born U.S. philosopher. He earned a doctorate in physics at the University of Jena in 1921. In 1926 he was invited to join the faculty of the University of Vienna, where he soon became an influential member of a group of philosophers, mathematicians, and scientists known as the Vienna Circle. Out of their discussions developed the basic ideas of logical positivism. Carnap immigrated to the U.S. in 1935 and taught at the University of Chicago (1936–52). After two years at the Institute for Advanced Study at Princeton (1952–54), he joined the faculty of the University of California at Los Angeles, where he remained until his death. Carnap sought to give the basic thesis of empiricism—that all concepts and beliefs about the world ultimately derive from immediate experience—a precise interpretation, construing it as a logical thesis about the evidential grounding of empirical knowledge. For Carnap, empiricism is the doctrine that the terms and sentences that express assertions about the world are “reducible” in a clearly specifiable sense to terms and sentences describing the immediate data of experience. His major works include The Logical Structure of the World (1928), The Logical Syntax of Language (1934), Introduction to Semantics (1942), Meaning and Necessity (1947), and The Logical Foundations of Probability (1950).
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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 who offered Carnap a position in his department, which Carnap took up in 1926. Carnap thereupon joined an informal group of Viennese intellectuals that came to be called the Vienna Circle, led by Moritz Schlick and including Hans Hahn, Friedrich Waismann, Otto Neurath, and Herbert Feigl, with occasional appearances 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) founded the philosophy journal Erkenntnis.
In 1928, Carnap published two important books:
In February 1930 Tarski lectured in Vienna, and in November 1930 Carnap visited Warsaw. On these occasions he learned much about Tarski's model theoretic approach to semantics. In 1931, Carnap was appointed Professor at the German language University of Prague. There he wrote the book that was to make him the most famous logical positivist and member of the Vienna Circle, his Logical Syntax of Language (Carnap 1934). In this work, Carnap advanced his Principle of Tolerance, according to which there is no such thing as a "true" or "correct" logic or language. One is free to adopt whatever form of language is useful for one's purposes. In 1933, Willard 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, under no illusions about what the Third Reich was about to unleash on Europe, and whose socialist and pacifist convictions made him a marked man, emigrated to the United States in 1935 and became a naturalized citizen in 1941. Meanwhile back in Vienna, Moritz Schlick was assassinated in 1936. From 1936 to 1952, Carnap was a professor of philosophy at the University of Chicago. Thanks in part to Quine's good offices, Carnap spent the years 1939-41 at Harvard, 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, Mortimer Adler, Charles Hartshorne, and Manley Thompson.) Carnap's years at Chicago were nonetheless highly productive ones. He wrote books on semantics (Carnap 1942, 1943, 1956), modal logic, coming very close in Carnap (1956) to the now-standard possible worlds semantics for that logic Saul Kripke proposed starting in 1959, and on the philosophical foundations of probability and induction (Carnap 1950, 1952).
After a stint at the Institute for Advanced Study at Princeton, he joined the philosophy department at UCLA in 1954, Hans Reichenbach having died the previous year. He had earlier declined an offer of a similar position at the University of California, because taking up that position required that he sign a McCarthy-era loyalty oath, a practice to which he was opposed on principle. While at UCLA, he wrote on scientific knowledge, the analytic - synthetic dichotomy, and the verification principle. His writings on thermodynamics and on the foundations of probability and induction, were published posthumously as Carnap (1971, 1977, 1980).
Carnap taught himself Esperanto when he was a mere fourteen years of age, and remained very sympathetic to it (Carnap 1963). He later attended the World Congress of Esperanto in 1908 and 1922, and employed the language while traveling.
Carnap had four children by his first marriage, which ended in divorce in 1929. His second wife committed suicide in 1964.
Online bibliography. Under construction, with no entries dated later than 1937. Most of Carnap's publications from 1940 onwards can be tracked via the web-based Philosopher's Index, to which most academic libraries subscribe.