Editing Stephen Cole Kleene

{{about|the American mathematician|the German mathematician, creator of the [[Klein Bottle]]|Felix Klein}}{{Short description|American mathematician (1909–1994)}}
{{More citations needed|date=September 2022}}
{{Infobox scientist
| name = Stephen Kleene
| image = Kleene.jpg
| caption =
| birth_date = {{birth date|1909|01|05}}
| birth_place = [[Hartford, Connecticut]], U.S.
| death_date = {{death date and age|1994|01|25|1909|01|05}}
| death_place = [[Madison, Wisconsin]], U.S.
| nationality = [[United States|American]]
| field = [[Mathematics]]
| work_institutions = [[University of Wisconsin–Madison]]
| alma_mater = [[Amherst College]]<br />[[Princeton University]]
| doctoral_advisor = [[Alonzo Church]]
| doctoral_students = [[Robert Lee Constable|Robert Constable]]<br />[[Joan Moschovakis]]<br />[[Yiannis Moschovakis]]<br />[[Nels David Nelson]]<br />[[Dick de Jongh]]
| known_for = {{collapsible list|title={{nbsp}}|
* Contributions to [[intuitionism]]
* [[Kleene–Mostowski hierarchy]]
* [[Kleene–Rosser paradox]]
* [[Kleene star]]
* [[Kleene's algorithm]]
* [[Kleene's theorem]]
* [[Realizability]]
* [[Regular expressions]]
* [[Smn theorem|Kleene's ''s''<sub>''mn''</sub> theorem]]
}}
| prizes = [[Leroy P. Steele Prize]] <small>(1983)</small><br />[[National Medal of Science]] <small>(1990)</small>
}}

'''Stephen Cole Kleene''' ({{IPAc-en|ˈ|k|l|eɪ|n|i}} {{respell|KLAY|nee}};{{efn|Although his last name is commonly pronounced {{IPAc-en|ˈ|k|l|iː|n|i}} {{respell|KLEE|nee}} or {{IPAc-en|k|l|iː|n}} {{respell|KLEEN}}, Kleene himself pronounced it {{IPAc-en|ˈ|k|l|eɪ|n|i}} {{respell|KLAY|nee}}.<ref>{{cite news |last=Pace |first=Eric |date=January 27, 1994 |title=Stephen C. Kleene Is Dead at 85; Was Leader in Computer Science |url=https://www.nytimes.com/1994/01/27/obituaries/stephen-c-kleene-is-dead-at-85-was-leader-in-computer-science.html |newspaper=The New York Times}}</ref> 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."<ref>In [http://foldoc.org/Stephen+Kleene Entry "Stephen Kleene"] at [http://foldoc.org/ Free Online Dictionary of Computing].</ref> However, many instances of this surname can be found in the Netherlands and Dutch pronunciation of 'ee' is as ay as in hail, but shorter. Probably, Kleene was aware of that.{{cn|date=December 2024}}}} January 5, 1909 – January 25, 1994) was an American [[mathematician]]. One of the students of [[Alonzo Church]], Kleene, along with [[Rózsa Péter]], [[Alan Turing]], [[Emil Post]], and others, is best known as a founder of the branch of [[mathematical logic]] known as [[recursion theory]], which subsequently helped to provide the foundations of [[theoretical computer science]]. Kleene's work grounds the study of [[computable function]]s. 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 fixed-point theorem]]. He also invented [[regular expressions]] in 1951 to describe [[artificial neural network|McCulloch-Pitts neural networks]], and made significant contributions to the foundations of mathematical [[intuitionism]].

==Biography==
Kleene was awarded a bachelor's degree from [[Amherst College]] in 1930. He was awarded a Ph.D. in mathematics from [[Princeton University]] in 1934, where 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, 1939–1940, 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 (United States)|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 (state)|New York]], and then a project director at the [[Naval Research Laboratory]] in [[Washington, D.C.]]

In 1946, Kleene returned to the University of Wisconsin-Madison, becoming a full professor in 1948 and the Cyrus C. MacDuffee professor of mathematics in 1964. He served two terms as the Chair of the Department of Mathematics and one term as the Chair of the Department of Numerical Analysis (later renamed the Department of Computer Science). He also served as Dean of the College of Letters and Science in 1969–1974. During his years at the University of Wisconsin he was thesis advisor to 13 Ph.D. students. He retired from the University of Wisconsin in 1979. In 1999 the mathematics library at the University of Wisconsin was renamed in his honor.<ref>{{cite web |title=S. C. Kleene |url=https://mathshistory.st-andrews.ac.uk/Biographies/Kleene/ |access-date=February 8, 2021}}</ref>

Kleene's teaching at Wisconsin resulted in three texts in [[mathematical logic]], Kleene (1952, 1967) and Kleene and Vesley (1965). The first two are 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 [[intuitionistic logic]] and mathematical [[intuitionism]].

{{blockquote|[...] recursive function theory is of central importance in computer science. Kleene is responsible for many of the fundamental results in the area, including the Kleene normal form theorem (1936), the Kleene recursive theorem (1938), the development of the arithmetical and hyper-arithmetical hierarchies in the 1940s and 1950s, the Kleene-Post theory of degrees of unsolvability (1954), and higher-type recursion theory. which he began in the late 1950s and returned to in the late 1970s. [...] Beginning in the late 1940s, Kleene also worked in a second area, Brouwer's intuitionism. Using tools from recursion theory, he introduced recursive realizability, an important technique for interpreting intuitionistic statements. In the summer of 1951 at the [[Rand Corporation]], he produced a major breakthrough in a third area when he gave an important characterization of events accepted by a [[finite automaton]].<ref>{{cite journal |author-last=Keisler |author-first=H. Jerome |author-link=H. Jerome Keisler |title=Stephen Cole Kleene 1909–1994 |journal=Notices of the AMS |date=September 1994 |volume=41 |issue=7 |page=792}}</ref>}}

Kleene served as president of the [[Association for Symbolic Logic]], 1956–1958, and of the International Union of History and Philosophy of Science,<ref>
[http://www.icsu.org/publicdb/frmDisplayMember?docid=97d44bb2b86ba6e145872f68db2d0d62 IUHPS website]; also known as "International Union of the History and the Philosophy of Science". A member of [http://www.icsu.org/ ICSU], the International Council for Science ([http://www.icsu.org/about-icsu/about-us/a-brief-history formerly named] International Council of Scientific Unions).</ref> 1961. The importance of Kleene's work led to [[Daniel Dennett]] coining the saying, published in 1978, that "Kleeneness is next to Gödelness."<ref>Daniel Dennett and Karel Lambert, "kleene", in ''The Philosophical Lexicon'', 7th ed. (Newark, DE: American Philosophical Association, 1978), 5; and ''Hyperborea'' (blogger pseudonym), "Dennett's Logocentric Lexicon" (9 December 2007): http://aeconomics.blogspot.com/2007/12/dennetts-logocentric-lexicon.html</ref> In 1990, he was awarded the [[National Medal of Science]].

Kleene and his wife Nancy Elliott had four children. He had a lifelong devotion to the family farm in Maine. An avid mountain climber, he had a strong interest in nature and the [[environment (biophysical)|environment]], and was active in many [[conservation movement|conservation]] causes.

==Legacy==
At each conference of the [[Symposium on Logic in Computer Science]] the [[Kleene Award]], in honour of Stephen Cole Kleene, is given for the best student paper.<ref>{{Cite web|url=http://lics.siglog.org/archive/kleene-award.html|title=LICS – Archive|website=lics.siglog.org}}</ref>

==Selected publications==
* 1935. {{cite journal |url=https://www.jstor.org/stable/2372027 |author-first=Stephen Cole |author-last=Kleene |author-link=Stephen Cole Kleene|display-authors=0|title=A Theory of Positive Integers in Formal Logic. Part I |journal=[[American Journal of Mathematics]]|volume=57 |number=1 |pages=153–173 |date=Jan 1935 |doi=10.2307/2372027 |jstor=2372027}}
* 1935. {{cite journal |url=https://www.jstor.org/stable/2371199 |author-first=Stephen Cole|author-last=Kleene |author-link=Stephen Cole Kleene|display-authors=0|title=A Theory of Positive Integers in Formal Logic. Part II |journal=American Journal of Mathematics |volume=57 |number=2 |pages=219–244 |date=Apr 1935 |doi=10.2307/2371199 |jstor=2371199}}
* 1935. {{cite journal |jstor=1968646 |author-first1=Stephen Cole|author-last1=Kleene |author-link1=Stephen Cole Kleene|author-first2=J. Barkley|author-last2=Rosser|author-link2=J. Barkley Rosser|author-mask=1|title=The Inconsistency of Certain Formal Logics |journal=Annals of Mathematics |series=2nd Series |volume=36 |number=3 |pages=630–636 |date=Jul 1935 |doi=10.2307/1968646}}
* 1936. {{cite journal |title=General recursive functions of natural numbers |journal=[[Mathematische Annalen]] |issue=112 |pages=727–742 |date=1936 |url=http://www.digizeitschriften.de/dms/img/?PID=GDZPPN002278499}}
* 1936. {{cite journal |url=https://projecteuclid.org/euclid.dmj/1077489488 
|author-first=Stephen Cole |author-last=Kleene |author-link=Stephen Cole Kleene|author-mask=0 |title=<math>\lambda</math>-definability and recursiveness |journal=Duke Mathematical Journal |volume=2 |number=2 |pages=340–352 |year=1936}}
* 1938. {{cite journal |url=http://www.thatmarcusfamily.org/philosophy/Course_Websites/Readings/Kleene%20-%20Ordinals.pdf |author-first=Stephen Cole |author-last=Kleene |author-link=Stephen Cole Kleene|author-mask=0 |title=On Notations for Ordinal Numbers |journal=Journal of Symbolic Logic |volume=3 |pages=150–155 |year=1938 |issue=4 |doi=10.2307/2267778 |jstor=2267778|s2cid=34314018 }}
* 1943. {{cite journal |doi=10.1090/S0002-9947-1943-0007371-8 |url=https://www.ams.org/journals/tran/1943-053-01/S0002-9947-1943-0007371-8/ |author-first=Stephen Cole |author-last=Kleene |author-link=Stephen Cole Kleene |author-mask=0 |title=Recursive predicates and quantifiers |journal=Transactions of the American Mathematical Society |volume=53 |number=1 |pages=41–73 |date=Jan 1943 |doi-access=free}}
* 1951. {{cite news |title=Representation of Events in Nerve Nets and Finite Automata |author-first=Stephen Cole |author-last=Kleene |author-link=Stephen Cole Kleene |display-authors=0|date=15 December 1951 |series=U. S. Air Force Project Rand Research Memorandum |number=RM-704 |url=https://www.rand.org/content/dam/rand/pubs/research_memoranda/2008/RM704.pdf |publisher=[[The RAND Corporation]]}}
* 1952. {{Cite book
|last=Kleene
|first=Stephen Cole
|author-link=Stephen Cole Kleene
|display-authors=0
|title=Introduction to Metamathematics
|publisher=Van Nostrand|location=New York
|year=1952
|oclc=523942
}}<ref>{{Cite book|last=Kleene|first=Stephen Cole|author-link=Stephen Cole Kleene|display-authors=0|title=reprint|publisher= [[Ishi Press]]|orig-year=1952|date=13 March 2009|isbn=9780923891572}}</ref>

* 1956. {{cite book |chapter=Representation of Events in Nerve Nets and Finite Automata |author-first=Stephen Cole |author-last=Kleene |author-link=Stephen Cole Kleene |display-authors=0|title=Automata Studies |editor-first1=Claude |editor-last1=Shannon |editor-link1=Claude Shannon |editor-first2=John |editor-last2=McCarthy |editor-link2=John McCarthy (computer scientist) |oclc=564148 |date=1956}}
* 1965 {{Cite book
|last1=Kleene
|first1=Stephen Cole
|author-link1=Stephen Cole Kleene
|author-last2=Vesley
|author-first2=Richard Eugene
|author-mask=1
|title=The Foundations of Intuitionistic Mathematics
|publisher=North-Holland
}}<ref>{{cite journal|author-last=Bishop|author-first=Errett|author-link=Errett Bishop |title=Review: The foundations of intuitionistic mathematics|journal=[[Bulletin of the American Mathematical Society]] |date=1965 |volume=71 |issue=6 |pages=850–852 |url=https://www.ams.org/journals/bull/1965-71-06/S0002-9904-1965-11412-4/S0002-9904-1965-11412-4.pdf |doi=10.1090/s0002-9904-1965-11412-4 |doi-access=free}}</ref>
* 1967. ''[https://www.worldcat.org/oclc/523472 Mathematical Logic.]'' [[John Wiley & Sons]]. Dover reprint, 2002. {{ISBN|0-486-42533-9}}.
* 1981. "Origins of Recursive Function Theory" in ''[https://www.worldcat.org/oclc/4583089 Annals of the History of Computing 3],'' No. 1.
* 1987. {{cite journal |author-first=Stephen Cole |author-last=Kleene |author-link=Stephen Cole Kleene|author-mask=0 |title=Reflections on Church's thesis |journal=Notre Dame Journal of Formal Logic |volume=28 |number=4 |pages=490–498 |date=Oct 1987 |doi=10.1305/ndjfl/1093637645 |doi-access=free}}

==See also==
* [[Kleene–Brouwer order]]
* [[Kleene–Rosser paradox]]
* [[Kleene's O]]
* [[Kleene's T predicate]]
* [[List of pioneers in computer science]]

==Notes==
{{Notelist}}

==References==
{{Reflist}}

==External links==
* {{MacTutor|id=Kleene}}
* [https://nap.nationalacademies.org/read/9649/chapter/10 Biographical memoir] – by [[Saunders Mac Lane]]
* [https://www.library.wisc.edu/amp/about-amp/history-of-the-amp-library/kleene/ Kleene bibliography]
* {{cite web |url=https://www.princeton.edu/~mudd/finding_aids/mathoral/pmc23.htm |title=The Princeton Mathematics Community in the 1930s: Transcript Number 23 (PMC23): Stephen C. Kleene and J. Barkley Rosser |url-status=dead |archive-url=https://web.archive.org/web/20150310074630/https://www.princeton.edu/~mudd/finding_aids/mathoral/pmc23.htm |archive-date=10 March 2015}} – Interview with Kleene and [[John Barkley Rosser]] about their experiences at Princeton
* {{DBLP|name=Stephen Cole Kleene}}

{{Winners of the National Medal of Science|math-stat-comp}}

{{Authority control}}

{{DEFAULTSORT:Kleene, Stephen Cole}}
[[Category:American computer scientists]]
[[Category:American logicians]]
[[Category:Amherst College alumni]]
[[Category:Computability theorists]]
[[Category:Educators from Hartford, Connecticut]]
[[Category:Institute for Advanced Study visiting scholars]]
[[Category:Intuitionism]]
[[Category:National Medal of Science laureates]]
[[Category:Princeton University alumni]]
[[Category:University of Wisconsin–Madison faculty]]
[[Category:1909 births]]
[[Category:1994 deaths]]
[[Category:20th-century American mathematicians]]
[[Category:Mathematicians from Connecticut]]