Rudolf Carnap

Verified Timeline

Lore & Background

Carnap was born Paul Rudolf Carnap on 18 May 1891 in Ronsdorf, in present-day Wuppertal, Germany. His father rose from being a poor ribbon-weaver to be the owner of a ribbon-making factory; his mother came from an academic family. As a ten-year-old, he accompanied his uncle, archaeologist Wilhelm Dörpfeld, on an expedition to Greece. At 14, he taught himself Esperanto and attended the World Congress of Esperanto in Dresden in 1908. He later attended the 1924 Congress in Vienna, where he met fellow Esperantist Otto Neurath for the first time. Raised in a profoundly religious Protestant family, he later became an atheist. Carnap studied at the University of Jena from 1910 to 1914, intending to write a thesis in physics. He studied Immanuel Kant's Critique of Pure Reason under Bruno Bauch and was one of the few students to attend Gottlob Frege's courses in mathematical logic. During World War I, he served in the German army despite moral and political opposition. After three years of service, he was given permission to study physics at the University of Berlin, 1917–18, where Albert Einstein was a newly appointed professor. In August 1918 Carnap joined the Independent Social Democratic Party and worked as a journalist for left-wing newspapers. He wrote a thesis defining an axiomatic theory of space and time, but the physics department said it was too philosophical, and Bruno Bauch of the philosophy department said it was pure physics; he then wrote a second thesis in 1921 under Bauch on the theory of space in a more orthodox Kantian style, published as Der Raum in a supplemental issue of Kant-Studien (1922). In 1926, Carnap accepted a position at the University of Vienna, joining the Vienna Circle directed largely by Moritz Schlick. He co-wrote the Circle's 1929 manifesto with Hahn and Neurath, and co-founded the philosophy journal Erkenntnis with Hans Reichenbach. In February 1930, Alfred Tarski lectured in Vienna, and during November 1930, Carnap visited Warsaw, learning much about Tarski's model-theoretic method of semantics. In 1931, Carnap was appointed Professor at the German University in Prague. In 1933, W. V. Quine met Carnap in Prague and discussed his work at length. Carnap emigrated to the United States in 1935 due to his socialist and pacifist beliefs, becoming a naturalized citizen in 1941. He taught at the University of Chicago from 1936 to 1952, then at UCLA from 1954 after Hans Reichenbach died the previous year. He was politically involved, signing an open appeal distributed by the National Committee to Secure Justice in the Rosenberg Case to appeal for clemency, and was listed as a sponsor for the "National Conference to Appeal the Walter-McCarran Law and Defend Its Victims" and for the "Scientific and Cultural Conference for World Peace."

Reader's Guide

Carnap's significance lies in his central role in the Vienna Circle and the development of logical positivism, a movement that sought to ground philosophy in the logical analysis of scientific language. His early work, Der Raum (1922), argued that there are three separate notions of space—formal, intuitive, and physical—and that philosophical contradictions often arise from misusing language, a theme that persisted throughout his career. He was instrumental in introducing the work of Gottlob Frege and Bertrand Russell to a wider audience; Frege's course exposed him to Russell's work, and Russell responded to Carnap's letter by copying by hand long passages from Principia Mathematica for Carnap's benefit. His engagement with Alfred Tarski's model-theoretic semantics led to his own work on the distinction between logical and non-logical constants and between logical and factual truth, as well as the concepts of intension and extension. Carnap's later work on probability and inductive logic (Carnap 1950, 1952), and his defense of the analytic–synthetic distinction and the verification principle, shaped mid-20th-century philosophy of science. His emigration to the United States helped transplant logical positivism to American academia, where he influenced figures such as W. V. Quine and Carl Gustav Hempel, who accepted an assistant position from Carnap in the late 1930s. Despite later criticisms, his systematic approach to philosophy and his efforts to clarify the foundations of science remain influential.

Did You Know?

• At age 10, Carnap accompanied his uncle, archaeologist Wilhelm Dörpfeld, on an expedition to Greece.
• At 14, Carnap taught himself Esperanto and attended the World Congress of Esperanto in Dresden in 1908.
• Carnap was one of the very few students to attend Gottlob Frege's courses in mathematical logic at the University of Jena.
• Bertrand Russell copied long passages from his Principia Mathematica by hand for Carnap because neither Carnap nor his university could afford a copy.
• Carnap's second wife, Elizabeth Ina Stöger, committed suicide in 1964.