# Hans Freudenthal, Selecta

## Editors

### Tonny A. Springer

Utrecht University, The Netherlands### Dirk van Dalen

Utrecht University, The Netherlands

Hans Freudenthal (1905–1990) was a Dutch mathematician, born in Luckenwalde, Germany. His scientific activities were of a rich variety. Enrolling at the University of Berlin as a student in the 1920s, he followed in the footsteps of his teachers, and became a topologist, but with a lively interest in group theory. Later in life, after a long journey through the realm of mathematics, working on almost all subjects that drew his interest, he turned towards the practical and methodological issues of the didactics of mathematics.

The present Selecta are devoted to Freudenthal’s mathematical oeuvre, they contain a selection of his major contributions. Included are fundamental contributions to topology such as the foundation of the theory of ends (in the thesis of 1931), the introduction (in 1937) of the suspension and its use in stability results for homotopy groups of spheres. In group theory there is work on topological groups (of the 1930s) and on various aspects of the theory of Lie groups, such as a paper on automorphisms of 1941. From the later work of the 1950s and 1960s, papers on geometric aspects of Lie theory (geometries associated to exceptional groups, space problems) have been included. Freudenthal’s versatility is further demonstrated by a choice from his foundational and historical work: papers on intuitionistic logic and topology, a paper on axiomatic geometry reappraising Hilbert’s *Grundlagen*, and a paper summarizing his development of Lincos, a universal (“cosmic”) language.

The book also contains a sketch of Freudenthal’s life. Most of the selected papers are accompanied by brief comments.