Rudolf Carnap

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Rudolf Carnap.

Rudolf Carnap (May 18, 1891, Ronsdorf, Germany – September 14, 1970, Santa Monica, California) was an influential philosopher who was active in central Europe before 1935 and in the United States thereafter. He was a leading member of the Vienna Circle and probably the most prominent advocate for logical positivism and the program of the Vienna Circle, at least in the United States. Carnap wrote an enormous amount, and he (and Carl Hempel) did more to work out the details of the logical positivist program and thereby promote that program in America and elsewhere than anyone else.

Harvard philosopher and logician Willard Quine wrote, "Carnap is a towering figure. I see him as the dominant figure in philosophy from the 1930s onward, as Russell had been in the decades before. ...Some philosophers would assign this role rather to Wittgenstein, but many see the scene as I do." Hempel wrote, "Carnap's ingenious and illuminating methods of logical analysis and reconstruction, and the example he has set in his own work of rigorous but openminded and undogmatic philosophical inquiry, have provided a powerful stimulus for a precise analytic approach to philosophical problems." (Both quoted in The Logical Structure of the World, Open Court edition, back cover.)

Life

Carnap was born in a north German family that had been humble until his parents' generation. He began his formal education at the Barmen Gymnasium. 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 took Frege's courses in mathematical logic in 1910, 1913, and 1914; he was one of very few students to do so. After serving in the German army during WW 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 Freiburg, 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, published as "Der Raum: Ein Beitrag zur Wissenschaftslehre." [Carnap (1922)].

In 1921, Carnap wrote a fateful 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, in which he developed a rigorous formal version of empiricism, defining all scientific terms in phenomenalistic terms. The formal system of the Aufbau, as this book is often called by virtue of the central word of its German title Der Logische Aufbau der Welt, 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 process 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 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. Carnap 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 a World Congress of Esperanto and employed the language while traveling.

Carnap had four children by his first marriage to Ina, which ended in divorce in 1929. His second wife committed suicide in 1964.

Carnap's Method

Carnap's work and method were strongly characterized by an emphasis on clarity, and a conviction that clarity is achieved through expressing things in symbolic form. He himself wrote that from an early age

I began to apply symbolic notation, now more frequently in the Principia form than in Frege's, in my own thinking about philosophical problems or in the formulation of axiom systems. When I considered a concept or a proposition occurring in a scientific or philosophical discussion, I thought I understood it clearly only if I felt that I could express it, if I wanted to, in symbolic language. ("Autobiography," in Schilpp, The Philosophy of Rudolf Carnap, 11)

Carnap's View of the Structure of Scientific Theories

According to Carnap, a scientific theory is an axiomatized formal system, consisting of five parts:

(1) a formal language that includes logical and non-logical terms

(2) a set of logical-mathematical axioms and rules of inference

(3) a set of non-logical axioms that express the empirical part of the theory

(4) a set of meaning postulates that state the meaning of the non-logical terms; those terms formalize the analytic trughs of the theory

(5) a set of rules of correspondence that give an empirical interpretation of the theory

[adapted from The Internet Encyclopedia of Philosophy, http://www.utm.edu/research/iep/c/carnap.htm ]

For Carnap, and the Logical Positivists in general, the distinction between observational and theoretical terms was central and crucial. In Philosophical Foundations of Physics (1966), Carnap based this difference on a distinction between empirical and theoretical laws. An empirical law, he claimed, deals with things that can be observed or measured. Such a law can be confirmed by direct observtion. A theoretical law, however, deals with things that we cannot observe or measure, but that we can only infer from observation; it cannot be confirmed or justified by observation. It is a hypothesis that reaches beyond direct experience. In many cases the distinction is clear, but Carnap had to admit that it is sometimes arbitrary.

The Analytic-Synthetic Distinction

Immanuel Kant had made a distinction between analytic and synthetic statements and a priori and a posteriori ones. This made possible a fourfold classification of statements: analytic and synthetic a priori, and analytic and synthetic a posteriori. Everyone admitted that all analytic statements are a priori, so the analytic a posteriori category is empty. But what about syntheitc a priori statements — statements that say something new about the world in that the predicate is not merely "contained in" the subject, but are known before or apart from experience? Kant claimed that this is not an empty category, and he gave some mathematical and philosophical statements as examples. But the logical empiricists claimed that there are no such statements; that there are only two kinds of statements, the analytic a priori ones and the synthetic a posteriori ones. Much of Carnap's work was based on this conviction and his subsequent attempt to distinguish precisely between anlytic and synthetic statements — a conviction and program that was central to all the logical positivists or logical empiricists, but that was rejected in Willard van Orman Quine's seminal essay, Two Dogmas of Empiricism (first published in 1951).

In The Logical Syntax of Language (1934) Carnap attempted to develop a formal language in which mathematics and scientific theories could be expressed.

The Carnap-Quine Debate

From about December 1932 to July 1970, a month before Carnap's death, Rudolf Carnap and Willard Quine carried on a long and philosophically fruitful correspondence. Quine was the younger man and first dealt with Carnap as his teacher, but the two became strong friends and remained so until the end — they soon came to address one another as "Dear Carnap," because Carnap did not like his first name, and "Dear Van," as Quine was known to his friends — even though Quine eventually came to reject central points of Carnap's view.

The central disagreement was over what in technical philosophy is known as analyticity.

Logician

A good introduction to Carnap the logician is his Introduction to Symbolic Logic (1958). There we find:

• Fair attention paid to a number of philosophical points logic texts often slight;
• An indifference to metatheory;
• A fascination with formalized semantics;
• A casual attitude about proof, and no mention of natural deduction;
• Close attention paid to the logic of relations;
• Many interesting examples of axiomatic theories, many formulated in second order logic;
• A great debt owed to Whitehead and Russell's Principia Mathematica.

Critical Response to Carnap

From about the beginning of the 20th Century, with the logical work of Frege and then Whitehead and Russell, and especially with the formation and rise to prominence of the Vienna Circle, there was a great deal of hope and expectation among a group of philosophers that developments in formal logic and formal language(s), making things clear through a process of philosophical explication and clarification, would result in putting philosophy on a scientific-logical footing and would enable it to dispense with and supercede its received tradition of lack of clarity, slipperiness of meaning, metaphysical mumbo-jumbo, and mysterious and suspect intuitions and other ill-defined and even more ill-understood concepts and methods. Carnap's work can be understood as taking up and championing this approach and going farther with it than anyone else. Although many other philosophers also participated with him or followed in his wake, Carnap has frequently been called and/or understood to be the most outstanding or paramount Logical Positivist. His attitude, approach, and aims held sway in one branch of Western philosophy until about the beginning of the 1960s.

Philosophy

For a precis of Carnap's philosophical conclusions, click here.

Academic Genealogy
Notable teachers	Notable students
Bruno Bauch Albert Einstein Gottlob Frege Edmund Husserl	David Kaplan

See also

• logical positivism
• Vienna Circle
• Philosophy of Science
• skeptic

Selected publications

• 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 and Pseudoproblems in Philosophy. University of California Press. Also: Chicago and La Salle IL: Open Court, 2003.
• 1929. Abriss der Logistik, mit besonderer Berücksichtigung der Relationstheorie und ihrer Anwendungen, Vienna: Springer.
• 1934. Logische Syntax der Sprache. English translation 1937, The Logical Syntax of Language. Kegan Paul.
• 1935. Philosophy and Logical Syntax, London: Kegan Paul.
• 1936. "Testability and Meaning," in Philosophy of Science III (1936) and IV (1937).
• 1938. "Logical Foundations of the Unity of Science," in International Encyclopaedia of Unified Science, vol. I n. 1, Chicago: University of Chicago Press.
• 1939. Foundations of Logic and Mathematics in International Encyclopedia of Unified Science, Vol. I, no. 3, Chicago: University of Chicago Press.
• 1942. Introduction to Semantics, Cambridge, MA: Harvard University Press.
• 1943. Formalization of Logic, Cambridge, MA: Harvard University Press.
• 1947. Meaning and Necessity: a Study in Semantics and Modal Logic, Chicago: University of Chicago Press.
• 1950. Logical Foundations of Probability, Chicago: University of Chicago Press
• 1950. "Empiricism, Semantics, Ontology," Revue Internationale de Philosophie 4: 20-40.
• 1952. The Continuum of Inductive Methods, Chicago: University of Chicago Press.
• 1958. Introduction to Symbolic Logic with Applications, New York: Dover.
• 1963, "Intellectual Autobiography," and "Replies and Systematic Expositions," in Schilpp (1-84; 859-1013).
• 1966. Philosophical Foundations of Physics, Martin Gardner, ed., New York: Basic Books.
• 1971. Studies in inductive logic and probability, Vol. 1. University of California Press.
• 1977. Two essays on entropy, Abner Shimony, ed., University of California Press.
• 1980. Studies in inductive logic and probability, Vol. 2, R.C. Jeffrey, ed., University of California Press.
• 1990. Dear Carnap, Dear Van: The Quine-Carnap Correspondence and Related Work, Ed. and Introduction by Richard Creath, Berkeley, Los Angeles, London: Universiy of California Press.

Most of Carnap's publications from 1940 onwards can be tracked via the web-based Philosophy Index, to which most academic libraries subscribe.

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, Paul Arthur, ed., 1963. The Philosophy of Rudolf Carnap. LaSalle IL: Open Court. (Essential for Carnap's "Autobiography," and his "Replies and Systematic Expositions," in response to his critics. Also contains a thorough bibliography of Carnap's writings to 1961, as well as a list of works to appear.)
• 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.

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."

External links

• Rudolf Carnap Webpage and Directory of Internet Resources
• Rudolf Carnap Collection at the University of Pittsburgh.
• Homepage of the Collected Works of Rudolf Carnap.
• Internet Encyclopedia of Philosophy: Rudolf Carnap by Mauro Murzi.
• Precis of Carnap's philosophy.

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