Church

Alonzo Church was born on June 14, 1903, in Washington, D.C., to Samuel Robbins Church, a justice of the Municipal Court of the District of Columbia, and Mildred Hannah Church (née Parker). His great-grandfather, also named Alonzo Church, was professor of mathematics and, later, president of the college in Athens, Georgia, from 1829 to 1859. Church received his A.B. degree (1924) and Ph.D. degree (1927) from Princeton University under the guidance of Oswald Veblen. Church's doctoral dissertation was published in the January 1927 issue of Transactions of the American Mathematical Society, and titled "Alternatives to Zermelo's Assumption." He went on to study at Harvard University for a year (1927-28) on a National Research Fellowship, followed by a year abroad (1928-29) on an International Research Fellowship at the Universities of Göttingen and Amsterdam (where he visited with L. E. J. Brouwer). Church was appointed Assistant Professor of Mathematics at Princeton in 1929, promoted to Associate Professor in 1939, received tenure in 1947; from 1961 to 1967 he was Professor of Mathematics and Philosophy.

When the Association for Symbolic Logic was founded in 1935, Church became one of its first officers and the first co-editor (with C. H. Langford) of the Journal of Symbolic Logic. The first issue of the journal was published in March 1936, and Church served as editor of reviews for its first 44 volumes (1936-79). As a result of the high standards he set for the reviews section, Church was instrumental in building respect for the field of symbolic logic among mathematicians and philosophers.

During the 1930s, Church made Princeton a leading center of research in mathematical logic, with a focus on questions of the completeness and decidability of logical systems. In 1936 he demonstrated the undecidability of first-order logic ("Church's Theorem"), thus extending the famous result of Kurt Gödel, who was visiting the Institute for Advanced Study at the time. Together with his early students, J. Barkley Rosser, Steven C. Kleene, and Alan M. Turing, Church established the equivalence of the lambda calculus, recursive function theory, and Turing machines as formalizations of the notion of "effective calculability," a result that has come to be known as the "Church-Turing Thesis." In the 1950s and 1960s another generation of Church's students, including Michael Rabin, Hartley Rodgers, and Dana Scott, extended this research to automata, formal languages, and formal semantics, thus shaping the new field of theoretical computer science. Through this work—the lambda calculus—one of Church's earliest creations, gained new life as the basis for functional programming languages and for denotational semantics.

In 1967, Church moved his Journal of Symbolic Logic office's operations from Princeton to Los Angeles and continued his teaching career as Professor of Philosophy and Mathematics at UCLA until his retirement in 1990.

Church's writings range from papers published in numerous academic journals and books, to his 1941 monograph The Calculi of Lambda-Conversion and 1956 textbook An Introduction to Mathematical Logic, and to articles in the Encyclopedia Britannica for which he served as consulting editor on topics of mathematics and philosophy.

Church was elected to the National Academy of Sciences in 1978 and was also a member of the American Academy of Arts and Sciences and British Academy. He received honorary degrees from Case Western Reserve University (1969), Princeton University (1985) and the State University of New York at Buffalo (1990). The following statement was read aloud during the Princeton ceremony:

Over some 40 years of research and teaching, he made Princeton an international center of symbolic logic. In work contributing to what has been termed 'a fundamental discovery of the mathematicizing power of Homo Sapiens,' he defined the central question concerning the boundaries of formal reasoning. As longstanding editor and reviewer for his discipline's journal, he gave critical guidance to its quest for the foundations of mathematics and chronicled its history. Through his students, he set a path that has led from the abstract realm of mathematical logic to the concrete domains of computer science and to new vistas of mathematical power.

Church was married to Mary Julia Kuczinski from 1925 until her death in 1976, and they had three children—Alonzo Church, Jr. (Princeton Class of 1951), Mary Ann Addison, and Mildred Warner Dandridge. Several other of Church's relatives also attended Princeton University, including Church's grandsons John West Addison III (Class of 1984) and Alonzo Addison (Class of 1987), and three of Church's uncles. The uncle who was also named Alonzo Church was a member of the Class of 1892; James Robb Church belonged to the Class of 1888; and W. W. "Will" Church was in the Class of 1897. Following his retirement from UCLA, Alonzo Church moved to Hudson, Ohio, where his son resided. Church died on August 11, 1995, and was buried in the family plot in the Princeton Cemetery.