K. Jon Barwise, a former Stanford professor renowned for his research in mathematical logic, his ingenuity in applying mathematical techniques to outstanding problems in other disciplines, and his pioneering efforts in logic pedagogy, died of cancer March 4 in Bloomington, Ind. He was 57.

Barwise was a co-founder and the first director of the Center for the Study of Language and Information at Stanford, and the first director of the Symbolic Systems Program. He taught at Stanford from 1979 to 1981, and from 1983 to 1990. At the time of his death he was College Professor of Philosophy, Computer Science and Mathematics at Indiana University, where he joined the faculty in 1990.

"From the European perspective," said Johan van Benthem of the University of Amsterdam, "Jon was one of those people who define a whole field. Many students and colleagues on other continents who had never even met him felt their work shaped by the force of his ideas and personality -- because of the power of his publications."

Barwise was born in Independence, Mo., on June 29, 1942, to Kenneth T. and Evelyn Barwise. He attended Yale University, where he received his bachelor's degree in mathematics and philosophy in 1963. He received his doctorate in mathematics in 1967 from Stanford, where he studied logic under Professor Solomon Feferman of Stanford and Professor Dana Scott, now at Carnegie Mellon University. In 1992 he was awarded an honorary doctorate from the University of Pennsylvania.

"Jon was a builder," said Feferman. "He liked carpentry and remodeling houses and helping to create new academic projects and programs, however much time and effort they took. In pursuing these, he carried people along with his convictions and enthusiasms, never insistent, always good-humored."

Prior to Stanford, Barwise held appointments in mathematics and computer science at Yale and the University of Wisconsin. He also held one-year visiting positions at Oxford University and the University of California-Los Angeles, and was twice a fellow at the Center for Advanced Study in the Behavioral Sciences at Stanford.

Throughout his prolific career,
Barwise sought to develop a better theoretical understanding of
information content: how it is expressed in language, computers or
graphical representations, and how it is transferred from one form
of representation to another. His first book, *Admissible Sets
and Structures* (1975), developed the theory of admissible sets
and applied it to definability theory, a branch of logic devoted to
the precise study of the expressive power of formal languages (for
example, mathematical languages). The techniques he pioneered in
this work are still being applied and extended today.

*Situations and Attitudes*
(1983), his second book, coauthored with Professor John Perry of
Stanford, introduced the notion of situation semantics, a broadly
philosophical and mathematical approach to the study of meaning in
natural (i.e., spoken human) languages. Situation semantics and
situation theory are today one of several tools used by linguists
studying the rules that determine the information content of
sentences in a language.

Barwise's third book, *The Liar:
An Essay on Truth and Circularity* (1987), coauthored with
Professor John Etchemendy of Stanford, combined ideas from
situation semantics and insights of the British philosopher of
language J. L. Austin to study circular or self-referential claims,
such as the so-called Liar Paradox ("What I am now saying is
false"). New developments in non-well-founded set theory by the
mathematician Peter Aczel of Manchester University were used to
give a precise, non-paradoxical model of these circular
claims.

With Professor Larry Moss of
Indiana, Barwise continued to pursue the theory of non-well-founded
sets and to apply it to a wide variety of circular phenomena in
computer science, linguistics and logic. This work was presented in
a fourth book, *Vicious Circles: On the Mathematics of Circular
Phenomena* (1996).

In his fifth research monograph,
*Information Flow: The Logic of Distributed Systems* (1997),
coauthored with Jerry Seligman, Barwise proposed a theory of how
information flows through complex systems as diverse as computers
and natural languages. Central to this theory is the notion of an
information channel, capable of preserving information as it is
transmitted through a complex, causally interacting
system.

Barwise's extensive contributions to logic went well beyond the topics of these five monographs. He authored or co-authored nearly 100 articles on topics ranging from infinitary logic (the logic of formal languages allowing infinitely long sentences) to generalized quantifiers (phrases like "most people," "few dogs," "many prime numbers") and heterogeneous inference (reasoning that employs information represented in more than one form, such as a map and written directions).

He also edited several landmark
volumes in logic, including *The Syntax and Semantics of
Infinitary Languages* (1968), *The Handbook of Mathematical
Logic* (1975), *Model-theoretic Logics* (with Solomon
Feferman, 1985) and *Logical Reasoning with Diagrams* (with
Gerard Allwein of Indiana University, 1996).

In addition to his substantial
research contributions, Barwise was deeply committed to the
teaching of logic. With Etchemendy, he developed numerous pieces of
innovative courseware to help convey abstract concepts in logic.
These were published with a series of textbooks, including *The
Language of First-order Logic* (1990), *Tarski's World*
(1991), *Turing's World* (1993), *Hyperproof* (1994) and
*Language, Proof and Logic* (2000).

"Jon always said that he considered his most important contribution to logic to be his development of new teaching techniques and methods," said Etchemendy.

Barwise and Etchemendy shared the 1997 Educom Medal for their contribution to logic pedagogy. Educom is a nonprofit consortium of colleges, universities and other organizations dedicated to the transformation of higher education through the application of information technologies. It has 600 institutional members and nearly 100 corporate associates.

During the last year of his life, Barwise conducted an extensive e-mail correspondence with family, friends and colleagues, cataloging his courageous efforts to deal with and surmount his illness, and his philosophical reflections on life, death and logic.

"Jon taught us how to die," said Irene Scott, wife of Barwise's teacher Dana Scott.

"Jon will be sorely missed as one of the key thinkers and leaders pursuing a broad vision of logic as an analysis of information and cognition," said van Benthem. "My own world suddenly seems lonelier."

Barwise is survived by his wife, Mary Ellen, of Bloomington, and three children: Melanie of Madison, Wis.; Jon Russell of Portland, Ore.; and Claire of Bloomington.

A memorial service will be held at Indiana University in Bloomington on Sunday, April 30. For more information call (812) 855-1093, (812) 855-7088, or see http://www-vil.cs.indiana.edu/barwise.html SR

Donations may be made to Ting-Sha
Institute (Cancer Retreat Center), P.O. Box 226, Pt. Reyes Station,
CA 94956.