Dear Istvan,

Unfortunate family circumstances prevent me from attending
this week's special event, much as I wished to. But they do
*not* prevent me from being fully aware of what your work
and person mean to me - and to many people worldwide.

Of course, your academic qualities as a research leader with
broad vision are a matter of public record. I cannot conceive
of algebraic logic today without your vitalizing influence.
Moreover, your achievements there spill over into other areas,
such as modal logic, and indeed, standard first-order logic.

I count myself fortunate in having had a long history of
cooperation with you and your impressive group, especially,
Hajnal and Ildiko. It started with clever Hungarian students
of yours like Szabolcs Mikulas attacking problems in mathematical
linguistics, like relational completeness of the Lambek Calculus.
This made me realize once more, after my earlier happy history
with Wim Blok, how fruitful algebraic logicians can be, once
they unleash their powers outside their narrower territory.

Next, our joint work on modal logic and the guarded fragment
has been a kind of breakthrough in thinking about the balance
between expressive power and complexity, whose repercussions
are still noticeable. I hope we can sit down one day, and do
still more - e.g., on second-order and fixed-point extensions.

Finally, the Budapest-Amsterdam exchanges have initiated a flow
of student talent which has enriched our communities immensely.
I will not even begin to enumerate all names, but just think of
Yde, Maarten, Eva, Szabolcs, Agnes, Andras. This network itself
may be the more lasting result of our decade of acquaintance.

By the way, I have taken good note of the fact that 'Budapest' is
now all about the logic of relativity. A much more modest Physics
Turn has taken place in my own interests on space, and modal logics
of geometry. Again, there might be reasons for synchronizing here.

As we all know, the real academic Success Formula has two variables:
Achievement and Charisma. You certainly have both, and I myself
often ponder the mysteries of your personality. One high point
which comes to mind is a meeting with Hajnal and you in a super-
heated Amsterdam hotel room near Artis, where I had to enter
through a blanket at the door (like initiation rites of Ancient
cults), and was then fed endless small cups of strong coffee,
which seemed your only source of sustenance in times of illness.
A little relativistic time-warp outside of our bleak Dutch reality.

This was just one of many memorable meetings, in Budapest, Warsaw,
or Amsterdam. I regret we cannot add one more just now, but I do
congratulate you and Hajnal, and all those gathered around you today.

Johan van Benthem

____________________________________________________


Institute for Logic, Language and Computation (ILLC)
University of Amsterdam, Plantage Muidergracht 24
1018 TV AMSTERDAM, The Netherlands
ph. +31 20 5256051, fax +31 20 5255206
http://staff.science.uva.nl/~johan/