Wim Blok, September 29, 1976	Wim Blok, Picture from his UIC webpage

This week the sad and totally unexpected news has come to us that our respected colleague Wim Blok has died in a fatal accident.

Wim Blok was a professor of mathematics at the University of Illinois at Chicago, and one of the leading researchers worldwide in the field of algebraic logic, a branch of mathematics which goes back to the nineteenth century, which seeks to understand and solve logical problems using tools from universal algebra.

Blok studied at the University of Amsterdam, and obtained his Ph.D. degree there. His first interest was set-theoretic topology, then represented at Amsterdam by the well-known topologist J. de Groot. After the latter's untimely death, and inspired by a visit of Philip Dwinger to Amsterdam, Blok's interest turned to algebraic logic. This resulted in his dissertation on "Varieties of Interior Algebras", prepared under the guidance of Dwinger, which was defended at the University of Amsterdam in 1976, with Anne Troelstra acting as the co-promotor (second referee).

In this first phase as a researcher at Amsterdam during the 1970s, Blok made seminal contributions to the field of modal and related logics. His dissertation and its follow-up publications transformed the study of completeness and incompleteness phenomena for modal and intuitionistic systems. More generally, its use of new powerful algebraic methods strongly influenced the Amsterdam modal semanticists of that period, leading to various publications and life-long subsequent contacts.

In the 1980s, Wim Blok moved to North-America, and initiated a new line of thought in abstract algebraic logic which was to have similar broad impact. In particular, he gave a lot of thought to the question what it could mean for a logic to have an algebraic semantics. With Don Pigozzi and others, he set up an entire framework for the study of logics by algebraic means. Their publications, notably `Algebraizable Logics' (Memoirs of the American Mathematical Society, 1989; cf. the MathSciNet review by Hajnal Andréka) have become classic sources.

Wim Blok was a regular visitor at the ILLC. When visiting his family and friends in the Netherlands he would usually spend some time at our institute, and often give a presentation of his work. Only a few years ago, he spent a sabbatical in Amsterdam, during which he gave a much appreciated course in abstract algebraic logic. We were just making plans to intensify this collaboration, and more particularly, preparing another extended visit.

It is with great sadness that we announce the loss of this respected colleague. No doubt, the same will be felt in many places in the international community, given Wim Blok's broad reputation and activity. At the same time, we also lose a good friend, as Wim's personality was famous for its warmth and genuine human interest in the work and lives of others. Our thoughts go out to the family he leaves behind: his wife Mary and son Philip in Chicago, and his relatives in our country.

Johan van Benthem
Peter van Emde Boas
Dick de Jongh
Anne Troelstra
Yde Venema
(December 8th, 2003)

Obituary from the Chicago Sun-Times, dated December 6th, 2003.