Gerhard Gentzen in Prague, 1945.
November 24, 1909|
|Died||August 4, 1945
|Alma mater||"University of Göttingen|
|"Doctoral advisor||"Paul Bernays|
Gerhard Karl Erich Gentzen (November 24, 1909 – August 4, 1945) was a "German "mathematician and "logician. He made major contributions to the "foundations of mathematics, "proof theory, especially on "natural deduction and "sequent calculus. He died in 1945 after the "Second World War, because he was deprived of food after being arrested in "Prague.
Gentzen was a student of "Paul Bernays at the "University of Göttingen. Bernays was fired as "non-"Aryan" in April 1933 and therefore "Hermann Weyl formally acted as his supervisor. Gentzen joined the "Sturmabteilung in November 1933 although he was by no means compelled to do so. Nevertheless he kept in contact with Bernays until the beginning of the "Second World War. In 1935, he corresponded with "Abraham Fraenkel in Jerusalem and was implicated by the Nazi teachers' union as one who "keeps contacts to the "Chosen People." In 1935 and 1936, "Hermann Weyl, head of the Göttingen mathematics department in 1933 until his resignation under Nazi pressure, made strong efforts to bring him to the "Institute for Advanced Study in Princeton.
Between November 1935 and 1939 he was an assistant of "David Hilbert in Göttingen. Gentzen joined the "Nazi Party in 1937. In April 1939 Gentzen swore the oath of loyalty to "Adolf Hitler as part of his academic appointment. From 1943 he was a teacher at the "University of Prague. Under a contract from the "SS Gentzen evidently worked for the "V-2 project.
Gentzen was arrested during the "citizens uprising against the occupying German forces on May 5, 1945. He, along with the rest of the staff of the German University in "Prague was subsequently handed over to Russian forces. Because of his past association with the SA, NSDAP and "NSD Dozentenbund, Gentzen was detained in a prison camp, where he died of malnutrition on August 4, 1945.
Gentzen's main work was on the foundations of "mathematics, in "proof theory, specifically "natural deduction and the "sequent calculus. His "cut-elimination theorem is the cornerstone of "proof-theoretic semantics, and some philosophical remarks in his "Investigations into Logical Deduction", together with "Ludwig Wittgenstein's later work, constitute the starting point for "inferential role semantics.
Gentzen "proved the consistency of the "Peano axioms in a paper published in 1936. In his "Habilitationsschrift, finished in 1939, he determined the proof-theoretical strength of Peano arithmetic. This was done by a direct proof of the unprovability of the principle of transfinite induction, used in his 1936 proof of consistency, within Peano arithmetic. The principle can, however, be expressed in arithmetic, so that a direct proof of "Gödel's incompleteness theorem followed. "Gödel used a coding procedure to construct an unprovable formula of arithmetic. Gentzen's proof was published in 1943 and marked the beginning of "ordinal proof theory.