Rudolph Carnap

Rudolf Carnap (May 18, 1891 – September 14, 1970) was an influential German-born philosopher who was active in Europe before 1935 and in the United States thereafter. He was a leading member of the Vienna Circle and a prominent advocate of logical positivism.

Life and work
Carnap was born to a west German family that had been humble until his parents' generation. He began his formal education at the Barmen Gymnasium in Wuppertal. From 1910 to 1914, he attended the University of Jena, intending to write a thesis in physics. But he also carefully studied Kant's Critique of Pure Reason in a course taught by Bruno Bauch, and was one of very few students to take Frege's courses in mathematical logic. After serving in the German army during World War I for three years, he was given permission to study physics at the University of Berlin, 1917–18, where Albert Einstein was a newly appointed professor. Carnap then attended the University of Jena, where he wrote a thesis setting out an axiomatic theory of space and time. 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, under Bauch's supervision, on the theory of space from a more orthodox Kantian point of view, and published as Der Raum (Space) in a supplemental issue of Kant-Studien (1922). In 1921, Carnap wrote a letter to Bertrand Russell, who responded by copying out by hand long passages from his Principia Mathematica for Carnap's benefit, as neither Carnap nor Freiburg could afford a copy of this epochal work. In 1924 and 1925, he attended seminars led by Edmund Husserl, the founder of phenomenology, 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 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:
 * The Logical Structure of the World (German: "Der logische Aufbau der Welt"), in which he developed a rigorous formal version of empiricism, defining all scientific terms in phenomenalistic terms. The formal system of the Aufbau (as the work is commonly called) was grounded in a single primitive dyadic predicate, which is satisfied if two individuals "resemble" each other. The Aufbau was greatly influenced by Principia Mathematica, and warrants comparison with the mereotopological metaphysics A. N. Whitehead developed over 1916-29. It appears, however, that Carnap soon became somewhat disenchanted with this book. In particular, he did not authorize an English translation until 1967.
 * Pseudoproblems in Philosophy asserted that many philosophical questions were meaningless, i.e., the way they were posed amounted to an abuse of language. An operational implication of this radical stance was taken to be the elimination of metaphysics from responsible human discourse. This is the notorious position for which Carnap was best known for many years.

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 murdered 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 in 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.

Logical Syntax
Carnap's Logical Syntax of Language can be regarded as a response to Wittgenstein 's Tractatus.

Carnap elaborated and extended the concept of logical syntax proposed by Wittgenstein in the Tractatus (Section 3.325).

However, Wittgenstein stated that propositions cannot represent logical form.

Carnap disagreed. Wittgenstein proposed the idea of logical syntax. It is Carnap who designed, formulated and implemented the details of logical syntax in philosophical analysis. Carnap defined logical syntax as:

In the U.S, the concept of logical syntax helped the development of natural language processing and compiler design (the Parrot virtual machine and LLVM).

The aim of logical syntax
The aim of logical syntax is to provide a system of concepts, a language, by the help of which the results of logical analysis will be exactly formulable.

Carnap stated :

Carnap wanted only to end metaphysics but not philosophy.

The Rejection of Metaphysics
Carnap, in his book Philosophy and Logical Syntax, used the concept of verifiability to reject metaphysics.

The function of logical analysis
Carnap used the method of logical analysis to reject metaphysics.

The question is : What reasons can there be to assert this proposition; or: How can we become certain as to its truth or falsehood?

Selected publications
Online bibliography. Under construction, with no entries dated later than 1937.
 * 1922. Der Raum: Ein Beitrag zur Wissenschaftslehre, Kant-Studien, Ergänzungshefte, no. 56. His Ph.D. thesis.
 * 1926. Physikalische Begriffsbildung. Karlsruhe: Braun.
 * 1928. Scheinprobleme in der Philosophie (Pseudoproblems of Philosophy). Berlin: Weltkreis-Verlag.
 * 1928. Der Logische Aufbau der Welt. 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.
 * 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.
 * 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 online.
 * 1950. "Empiricism, Semantics, Ontology", Revue Internationale de Philosophie 4: 20-40.
 * 1952. The Continuum of Inductive Methods. University of Chicago Press.
 * 1958. Introduction to Symbolic Logic with Applications. Dover.
 * 1963, "Intellectual Autobiography" in Schilpp (1963: 1-84).
 * 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: Wissenschftliche Buchgesellschaft. 167 pp. ISBN 3-534-14298-5.

A more complete list of publications.

Other sources

 * Ivor Grattan-Guinness, 2000. In Search of Mathematical Roots. Princeton Uni. Press.
 * Willard Quine, 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, 21–24 May 1991. University of Pittsburgh Press.
 * Wagner, Pierre, ed., 2009. Carnap's Logical Syntax of Language. Palgrave Macmillan.

Quotations

 * "In science there are no 'depths'; there is surface everywhere." (From the 1929 Vienna Circle manifesto.)
 * When Wittgenstein scolded him for having books about the paranormal in his library, Carnap replied: "But Ludwig, it is only an empirical question."
 * "It is not our business to set up prohibitions, but to arrive at conventions… In logic there are no morals. Everyone is at liberty to build up his own logic, i.e. his own language, as he wishes. All that is required of him is that, if he wishes to discuss it, he must state his methods clearly, and give syntactical rules instead of philosophical arguments." The Logical Syntax of Language, §17 (1937)