Hans Reichenbach (/ˈraɪxənbɑːx/;[3]German:[ˈʁaɪçənbax]; September 26, 1891 – April 9, 1953) was a leadingphilosopher of science,educator, and proponent oflogical empiricism. He founded theGesellschaft für empirische Philosophie (Society for Empirical Philosophy) in Berlin in 1928, also known as the "Berlin Circle".Carl Gustav Hempel,Richard von Mises,David Hilbert andKurt Grelling all became members of the Berlin Circle.
In 1930, Reichenbach andRudolf Carnap became editors of the journalErkenntnis. He also made lasting contributions to the study ofempiricism based on atheory of probability; thelogic and thephilosophy of mathematics;space,time, andrelativity theory; analysis ofprobabilisticreasoning; andquantum mechanics.[4] In 1951, he authoredThe Rise of Scientific Philosophy, his most popular book.[5][6]
Hans was the second son of aJewish merchant, Bruno Reichenbach, who had converted toProtestantism. He married Selma Menzel, a school mistress, who came from a long line of Protestant professionals which went back to theReformation.[7] His elder brotherBernard played a significant role in theleft communist movement. His younger brother,Herman was a music educator.
After completing secondary school inHamburg, Hans Reichenbach studied civilengineering at theHochschule für Technik Stuttgart, andphysics,mathematics andphilosophy at various universities, includingBerlin,Erlangen,Göttingen andMunich. Among his teachers wereErnst Cassirer,David Hilbert,Max Planck,Max Born,Edmund Husserl, andArnold Sommerfeld.
Reichenbach was active inyouth movements and student organizations. He joined theFreistudentenschaft in 1910.[8] He attended the founding conference of theFreideutsche Jugend umbrella group atHoher Meissner in 1913. He published articles about the university reform, the freedom of research, and againstanti-Semitic infiltrations in student organizations. His older brother Bernard shared in this activism and went on to become a member of theCommunist Workers' Party of Germany, representing this organisation on theExecutive Committee of the Communist International. Hans wrote the Platform of theSocialist Student Party, Berlin which was published in 1918.[9] The party had remained clandestine until theNovember Revolution when it was formally founded with him as chairman. He also worked withKarl Wittfogel,Alexander Schwab and his other brother Herman at this time.[10] In 1919 his textStudent und Sozialismus: mit einem Anhang: Programm der Sozialistischen Studentenpartei was published byHermann Schüller, an activist with theLeague for Proletarian Culture. However following his attending lectures by Albert Einstein in 1919, he stopped participating in political groups.[11]
Reichenbach received a degree inphilosophy from theUniversity of Erlangen in 1915 and hisPhD dissertation on thetheory of probability, titledDer Begriff der Wahrscheinlichkeit für die mathematische Darstellung der Wirklichkeit (The Concept of Probability for the Mathematical Representation of Reality) and supervised byPaul Hensel andMax Noether, was published in 1916. Reichenbach served duringWorld War I on the Russian front, in the German army radio troops. In 1917 he was removed from active duty, due to an illness, and returned toBerlin. While working as a physicist and engineer, Reichenbach attendedAlbert Einstein's lectures on thetheory of relativity inBerlin from 1917 to 1920.
In 1920 Reichenbach began teaching at theTechnische Hochschule Stuttgart asPrivatdozent. In the same year, he published his first book (which was accepted as hishabilitation in physics at the Technische Hochschule Stuttgart) on the philosophical implications of thetheory of relativity,The Theory of Relativity and A Priori Knowledge (Relativitätstheorie und Erkenntnis Apriori), which criticized theKantian notion ofsynthetica priori. He subsequently publishedAxiomatization of the Theory of Relativity (1924),From Copernicus to Einstein (1927) andThe Philosophy of Space and Time (1928), the last stating the logical positivist view on the theory of relativity.
Reichenbach distinguishes between axioms of connection and of coordination. Axioms of connection are those scientific laws which specify specific relations between specific physical things, likeMaxwell’s equations. They describe empirical laws. Axioms of coordination are those laws which describe all things and area priori, likeEuclidean geometry and are “general rules according to which the connections take place”. For example the axioms of connection of gravitationalequations are based upon the axioms of coordination ofarithmetic.[12]
Another distinction of his was between the 'context of discovery' and 'context of justification'. The way scientists come up with ideas is not always the same as the way they justify them, and so as separate objects of study Reichenbach distinguished between them.[13]
In 1926, with the help of Albert Einstein, Max Planck andMax von Laue, Reichenbach became assistant professor in the physics department of the University of Berlin. He gained notice for his methods of teaching, as he was easily approached and his courses were open to discussion and debate. This was highly unusual at the time, although the practice is nowadays a common one.
In 1928, Reichenbach founded the so-called "Berlin Circle" (German:Die Gesellschaft für empirische Philosophie; English:Society for Empirical Philosophy). Among its members wereCarl Gustav Hempel,Richard von Mises, David Hilbert andKurt Grelling. TheVienna Circle manifesto lists 30 of Reichenbach's publications in a bibliography of closely related authors. In 1930 he andRudolf Carnap began editing the journalErkenntnis.
WhenAdolf Hitler becameChancellor of Germany in 1933, Reichenbach was immediately dismissed from his appointment at the University of Berlin under the government's so called "Race Laws" due to his Jewish ancestry. Reichenbach himself did not practise Judaism, and his mother was a German Protestant, but he nevertheless suffered problems. He thereupon emigrated toTurkey, where he headed the department of philosophy atIstanbul University. He introducedinterdisciplinary seminars and courses on scientific subjects, and in 1935 he publishedThe Theory of Probability.
In 1938, with the help ofCharles W. Morris, Reichenbach moved to theUnited States to take up a professorship at theUniversity of California, Los Angeles in itsPhilosophy Department. Reichenbach helped establish UCLA as a leading philosophy department in the United States in the post-war period.Carl Hempel,Hilary Putnam, andWesley Salmon were perhaps his most prominent students. During his time there, he published several of his most notable books, includingPhilosophic Foundations of Quantum Mechanics in 1944,Elements of Symbolic Logic in 1947, andThe Rise of Scientific Philosophy (his most popular book) in 1951.[5][6]
Reichenbach died unexpectedly of a heart attack on April 9, 1953. He was living in Los Angeles at the time, and had been working on problems in thephilosophy of time and on the nature ofscientific laws. As part of this he proposed a three part model of time in language, involving speech time, event time and — critically — reference time, which has been used by linguists since for describingtenses.[14] This work resulted in two books published posthumously:The Direction of Time andNomological Statements and Admissible Operations.
Hans Reichenbach manuscripts, photographs, lectures, correspondence, drawings and other related materials are maintained by the Archives of Scientific Philosophy, Special Collections, University Library System, University of Pittsburgh.[4] Much of the content has been digitized. Some more notable content includes: