Stephen Cole Kleene (January
5, 1909, Hartford,
Connecticut, USA – January
25, 1994, Madison,
Wisconsin) was an American mathematician who helped lay the foundations
for theoretical computer
science. One of many distinguished students of
Alonzo Church, Kleene, along with
Alan Turing,
Emil Post,
and others, is best known as a founder of the branch of
mathematical logic known as
recursion theory. Kleene's work grounds the
study of which functions are
computable. A number of mathematical
concepts are named after him:
Kleene
hierarchy,
Kleene algebra, the
Kleene star (Kleene closure),
Kleene's recursion theorem and
the
Kleene fixpoint theorem.
He also invented
regular
expressions, and was a leading American advocate of
mathematical intuitionism.
Kleene pronounced his last name ; and are common mispronunciations.
(His son, Ken Kleene, wrote: "As far as I am aware this
pronunciation is incorrect in all known languages. I believe that
this novel pronunciation was invented by my father.")
Biography
Kleene was
awarded the BA degree from Amherst College in 1930. He was awarded the Ph.D. in mathematics from
Princeton
University in 1934. His thesis, entitled
A Theory
of Positive Integers in Formal Logic, was supervised by
Alonzo Church. In the 1930s, he did
important work on Church's
lambda
calculus.
In 1935, he joined the mathematics department
at the University of Wisconsin–Madison, where he spent nearly all of his career.
After two years as an instructor, he was appointed assistant
professor in 1937.
While a
visiting scholar at the Institute for Advanced Study in Princeton, 1939-40, he laid the foundation for
recursion theory, an area that
would be his lifelong research interest. In 1941, he
returned to Amherst College, where he spent one year as an
associate professor of mathematics.
During
World War II, Kleene was a
lieutenant commander in the
United
States Navy. He was an instructor of navigation at the U.S.
Naval
Reserve's Midshipmen's School in New York, and then a
project director at the Naval
Research Laboratory in Washington, D.C.
In 1946,
Kleene returned to Wisconsin, becoming a full professor in 1948 and the Cyrus
C. MacDuffee professor of mathematics in 1964. He was chair
of the Department of Mathematics and Computer Science, 1962-63, and
Dean of the College of Letters and Science from 1969 to 1974. The
latter appointment he took on despite the considerable student
unrest of the day, stemming from the
Vietnam
War. He retired from the University of Wisconsin in 1979. The
mathematics library at the University of Wisconsin was renamed in
his honour.
Kleene's teaching at Wisconsin resulted in three texts in
mathematical logic, Kleene (1952, 1967)
and Kleene and Vesley (1965), often cited and still in print.
Kleene (1952) wrote alternative proofs to the
Gödel's incompleteness
theorems that enhanced their canonical status and made them
easier to teach and understand. Kleene and Vesley (1965) is the
classic American introduction to
intuitionist logic and
mathematics. Kleene's standing
among logicians is suggested by the witticism "Kleeneliness is next
to Gödeliness", a
pun on "Cleanliness is next to
godliness".
Kleene served as president of the
Association of Symbolic Logic,
1956-58, and of the
International Union of the History and the Philosophy of
Science, 1961. In 1990, he was awarded the
National Medal of Science.
Kleene and his spouse Nancy Elliott had four children. He had a
lifelong devotion to the family farm in Maine. An avid mountain
climber and
canoeist, he had a strong interest
in
nature and the
environment and was active in many
conservation causes.
Important publications
See also
References
External links