Fields of Scholarship
Automata theory
Semantics of programming languages
Modal logic
Topology
Category theory

Honours and Awards
Academia Europaea
American Association for the Advancement of Science
American Academy of Arts and Sciences
Association for Computing Machinery
British Academy
Finnish Academy of Sciences and Letters
New York Academy of Sciences
U.S. National Academy of Sciences
2003 Humbolt Stiftung Senior Visiting Scientst, Munich, Germany
1978 - 1979 Guggenheim Foundation Fellow
1963 - 1965 Alfred P. Sloan Research Fellow
2001 Bolzano Medal for Merit in the Mathematical Sciences, Czech Academy of Sciences
1997 Rolf Schock Prize in Logic and Philosophy Royal Swedish Academy of Sciences
1990 Harold Pender Award University of Pennsylvania
1976 Turing Award (with Michael Rabin), Association for Computing Machinery
1972 LeRoy P. Steele Prize, American Mathematical Society