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- Brief scientific biography
- Commitment to education
- Primary literature
- Secondary literature
- Obituaries

Heinrich Behnke was born on October 9, 1898 in Horn near Hamburg, son of a manufacturing family. He passed his school years in Hamburg, first at a Vorschule and then at the Realgymnasium, renamed Oberrealschule St. Georg, hence without learning the classical languages. In the last three grades, from 1915 on, Behnke was fortunate to have as mathematics teacher a recent graduate from Göttingen who succeeded in interesting him in mathematics and physics, although until then he had shown no particular abilities. In March 1918, he passed the Abitur in Hamburg, despite the difficult conditions for living and learning at the time of World War I. Well prepared by his mathematics teacher, he began to study mathematics and physics at the University of Göttingen, in the summer term of 1918. Göttingen was then the center for mathematics and Behnke was very lucky to have as his professors Landau, Caratheodory, and Erich Hecke. The first term was interrupted by his being drafted into the army - happily, not to the front, but rather to a calculation service. He returned to Göttingen in November 1918, continuing his studies until the summer term 1919. His mentor Hecke then decided to accept the call to the newly created university in Hamburg, and Behnke followed him. There he became acquainted with Otto Toeplitz, then professor in Kiel, a relationship that would soon prove decisive. In the summer term 1922, Behnke presented his doctoral dissertation, Über analytische Funktionen und algebraische Zahlen, and passed the doctorate exam.

In 1923, at a time of profound economic crisis, Behnke obtained a position as Assistent at Hamburg university. The next year, he passed the Habilitation exam, on function theory, and began lecturing in Hamburg. Extraordinarily early in his mathematical career, in 1927, he received the call for a full professorship at the University of Münster, in Westfalia. Hesitating at first, due to the Catholic character of that region and uncertainty about the perspectives of academic activities there, he decided to accept and succeeded in fact to develop mathematics at Münster into a highly acclaimed center, in particular for function theory. He established close international relations, in especially with France and there with Henri Cartan. Moreover, he became one of the editors of the Mathematische Annalen. A key work of the so-called funktionentheoretische school at Münster became the book, now a classic, Theorie der Funktionen mehrerer komplexer Veränderlichen (1934), elaborated jointly with his assistant Peter Thullen.

After 1933, contrary to most of the other universities, no mathematicians were dismissed in Münster. Thullen, however, decided to emigrate to flee the Nazi system. Behnke was in danger, due to his liberal thinking and since his son from the first marriage was regarded as "half-Jewish", but he managed to stay in his position and to maintain his international contacts. In the last period of WW II, some cooperation with Wilhelm Süss became established so that Behnke survived the end of the war in the Mathematisches Reichsinstitut in Oberwolfach.

After Germany was liberated from Nazism, Behnke was appointed as Dean at Münster, holding this position until 1949. In the post-war period, Behnke successfully continued to expand mathematics at Münster. At the same time, it was the period when he was most active in mathematics education. Retired in 1967, he remained a key figure in German and international mathematics and mathematics education.

Right from the beginning of his lecturing, Behnke invested much energy in effective teaching, in motivating students and in organizing tutoring activities. It proved enormously productive that Otto Toeplitz, who had the same intention of turning the traditionally problematic lecture courses for beginners into effective studies, moved to Bonn in 1928, shortly after Behnke's call to Münster. They cooperated closely in improving their teaching methods. For advanced students, they organized from 1928 on yearly joint seminars, called Sängerkriege. The great majority of Behnke's mathematics students were future mathematics teachers at secondary schools. Contrary to other mathematicians, he did not marginalize this professional orientation; rather, he took it seriously and aimed at optimizing their studies in view of preparing to improved teaching abilities. In fact, until the establishment of the Diplom degree in 1942 for graduates, which should open careers in industry, the teaching profession had been basically the only professional career for graduates of mathematical studies. But even after the establishment of two degrees, the Staatsexamen and the Diplom, and of two divergent careers, Behnke - and with him mathematics in Münster - remained committed to the Staatsexamen and to the formation of future teachers.

As a consequence of his close cooperation with Toeplitz on teacher education, in 1932 Behnke founded the journal Semesterberichte zur Pflege des Zusammenhangs von Universität und Schule aus den mathematischen Seminaren, which he edited together with Toeplitz. The title, promoting the connection between school and university, became emblematic for Behnke's program and for his emphasis on teacher education. In 1938, Behnke was forced to omit the name of Toeplitz in the subtitle and in 1940 the publication was interrupted, due to the war, but it resumed publication in 1950 and is still published today.

After World War II, Behnke systematically expanded his agenda for mathematics teaching. Having revived the Semesterberichte journal, he now transformed the former joint yearly meetings of the mathematical seminars of Bonn and Münster into a yearly conference, officially called "Tagung zur Pflege des Zusammenhangs zwischen Höherer Schule und Universität", but better known as the Pfingsttagung. And in 1951 he succeeded in promoting the establishment a ground-breaking institution, the "Seminar für Didaktik der Mathematik" - the first institutionalization of mathematics education at a German university. Seminare were traditional forms in German universities for specialised studies in given disciplines and for closer contact with the professors; they had been founded and extended since 1810 for the major university disciplines. While the former mathematical seminars had meanwhile mostly been transformed into mathematical institutes, no such form had ever before existed for mathematics education - the highest form of academic recognition had been two Habilitationen in Didaktik der Mathematik (Schimmack, Dingler) earlier that century. Hans-Georg Steiner became one of the first assistants at this seminar.

In 1958, Behnke began editing a five-volume Grundzüge der Mathematik für Lehrer an höheren Schulen, presenting modern mathematics for teachers at secondary schools. Having in so many respects become a true successor of Felix Klein, he eventually followed Klein's footsteps in organizational respect as well. Besides being active in IMU, he became, in 1951, a member of the committee that was to prepare the reestablishment of ICMI. This was realized in 1952, in Geneva, and Behnke was the first secretary-general of the renewed organization. The first activity was to prepare national trend reports for the next IMU congress in 1954, though on a smaller scale than those of the first IMUK: the state of mathematics teaching for 16- to 21-year-old students. Activating the German sub-committee of ICMI, Behnke succeeded in having that report ready by 1954. At the IMU Congress 1954 in Amsterdam, Behnke was elected president of the ICMI, for the period 1955 to 1958. For the next period, 1959 to 1962, he served as vice-president, and the two following periods, from 1963 to 1970, as member of the Executive Committee. Behnke participated at ICME 1 in Lyon; for ICME 3, in Karlsruhe, he acted as honorary president. Clearly, as regards mathematics teaching, his views were confined to secondary schools, and to European countries; for other parts of the world, he frankly confessed to not feeling competent (Behnke 1978, p. 271).

H. BEHNKE, PETER THULLEN 1934, Theorie der Funktionen mehrerer komplexer Veränderlichen, Berlin

H. BEHNKE 1947/1948, Vorlesungen über klassische Funktionentheorie, 2 vol.s, Münster

H. BEHNKE (Ed.) 1954, Der mathematische Unterricht für die sechzehn- bis einundzwanzigjährige Jugend in der Bundesrepublik Deutschland, Göttingen: Vandenhoeck & Ruprecht

H. BEHNKE, FRIEDRICH SOMMER 1955, Theorie der analytischen Funktionen einer komplexen Veränderlichen

H. BEHNKE 1956, Vorlesungen über allgemeine Zahlentheorie, Münster

H. BEHNKE, F. BACHMANN, K. FLADT, W. SÜss 1958-1971, Grundzüge der Mathematik für Lehrer an höheren Schule sowie für Mathematiker in Industrie und Wirtschaft. 5 vol.s, Göttingen

H. BEHNKE 1973, Das Haus Still und seine Freunde aus der Wissenschaft, Recklinghausen, Bongers

H. BEHNKE 1978, Semesterberichte, Göttingen

SANFORD L. SEGAL 2003, Mathematicians under the Nazis, Princeton, NJ

HEINZ GRIESEL 1978, Zur Vollendung des 80. Lebensjahres von Prof. Dr. Dr. h.c. Dr. h.c. Heinrich Behnke (Münster) am 9, Oktober 1978, Praxis der Mathematik, 20, 1, 305-306

OLAF KRAFFT, H. BEHNKE 1974, 50 Jahre Doktor der Mathematik, Mathematisch-Physikalische Semesterberichte, 21, 1-4

VOLKER R. REMMERT 2002, Ungleiche Partner in der Mathematik im 'Dritten Reich': Heinrich Behnke und Wilhelm Süss, Mathematische Semesterberichte, 49, 1, 11-27

GERT SCHUBRING 1985, Das mathematische Seminar der Universität Münster, 1831/1875 bis 1951, Sudhoffs Archiv, 69, 154 191

HEINRICH GRAUERT, REINHOLD REMMERT 1981, In memoriam Heinrich Behnke, Mathematische Annalen, 255, 1, 1-4

HORST TIETZ, H. BEHNKE 1980, Mathematisch-Physikalische Semesterberichte, 27, 1, 1-3

Author

Gert Schubring

Institut für Didaktik der Mathematik

Fakultät für Mathematik, Universität Bielefeld

gert.schubring@uni-bielefeld.de