Peter Aczel

[Nicola Gambino]

Dear colleagues and friends,

I write to let you know of the sad news that Peter Aczel passed away on August 1st.

As readers of this list surely know, Peter made many fundamental and deeply influential contributions to Logic, Computer Science, Category Theory, and Constructive Mathematics.

I had the good fortune of having him as PhD supervisor and we remained in contact since then. I always admired his clarity of thinking and his kindness. He will be deeply missed.

With best regards,
Nicola

=
Dr Nicola Gambino
Department of Mathematics, University of Manchester

[andrew....@gmail.com]

I was very saddened to read the news of Peter Aczel's death.

I greatly admired his work, not only for its content but also for its clarity. His promotion of informal rigorous reasoning in type theory that Andrej Bauer mentioned in another post is an example. He also had very nice handwriting! -- I found this out
when he very generously shared some of his unpublished work with me when I was a graduate student in the late 70s and early 80s. (He later examined my PhD thesis.)

RIP, Peter.

Andrew M. Pitts
Professor of Theoretical Computer Science
Department of Computer Science and Technology
University of Cambridge
William Gates Building
15 JJ Thomson Ave
Cambridge CB3 0FD, UK

[Douglas Bridges]

Thank you, Nicola, for letting me know this sad news. 

I got to know Peter during visits to Munich and at conferences. He was not only a very fine contributor to our subjects, but also a throughly decent man. 

Best, 
Douglas 

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[giovan...@email.it]

I'm finding very hard to choose the words to respond to Nicolas's sad
news. Any formulation of this message seems to me inadequate to
celebrate appropriately Peter's contribution, and the importance that
his work and his friendship have had to me.

I began to ear about Peter's work in proof theory and constructive
mathematics when I was an undergraduate student at the university of
Padova, around 1995. If I remember correctly, he came to spend a
sabbatical year at the Padova mathematics department two years later.
During his stay, he gave an introductory course on constructive
mathematics. I remember how I found unique his ability of giving crystal
clear presentation of fundamental concepts and proofs, at the same time
preserving their complexity and richness in shades.

As Nicola says in his message, this clarity of thinking, the capability
of getting to the root of the discussed matter, has been since something
I found unfailingly in each and every of his scientific contributions.

Peter has been an external referee of my Ph.D. thesis. I had the
privilege of collaborating with him, and of benefiting of a number of
conversations, on the occasion of many conferences, and when he invited
me in Manchester. I will always be grateful to him and his family for
their kind hospitality.

He knew and understood far more than he wrote. I vividly remember his
curiosity and the sparkle in his eyes when he got an idea to pursue,
even after his retirement, an enthusiasm I rarely found in younger
scholars. This curiosity, and desire of investigating new areas, are
perhaps responsible for the fact he did not bring the book draft with
Michael Rathjen on Constructive Set Theory to final version. If that
book had actually seen the light, I think the current landscape of
constructive mathematics would be considerably different.

Despite its clarity and importance, his work on constructive mathematics
has still largely to be understood by the wider constructivists
community.

As Nicola has written, he was a very kind person. However, he also was a
radically rigorous and intellectually honest scholar, he would not have
agreed with you on something for politeness. This characteristic made
his appreciations and criticism of great value for his interlocutor.

He will certainly be deeply missed.

Giovanni Curi

[Martin Escardo]

It is very sad for me to learn this, particularly because recently I
have been doing work building on his ideas. I have had many interactions
with him both in person and by email. He was always such a kind person.
And quick to learn new things with an ability to make sharp
contributions to them, for example in HoTT/UF at the 2013 special year
in the IAS. He will be deeply missed. Martin