Born in Amsterdam 20.XII.1932
Study at the University of Amsterdam – Ph.D. 1963 under Arend Heyting.
Since 1960 at Utrecht University. Till 1967 at the mathematics department, since then at the Philosophy department.
Retired 1997, reappointed for the History of logic and the philosophhy of mathematics.
In charge of the Brouwer Project. Published a biography of L.E.J. Brouwer with the Oxford University Press (1999, 2005). Further work in progress.
Knight of the Lion of the Netherlands (1998)
Medal (Akademiepenning) of the Koninklijke Academie van Wetenschap (2003)
Honorary member of the Koninklijk Wiskundig Genootschap (2007)