W. Ross Ashby

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W. Ross Ashby
W. Ross Ashby (1948).jpg
W. Ross Ashby (1948)
Born(1903-09-06)6 September 1903
London, England
Died15 November 1972(1972-11-15) (aged 69)
Known forCybernetics, Law of Requisite Variety, Principle of Self-organization
Scientific career
FieldsPsychiatry, Cybernetics, Systems theory
InfluencesGerd Sommerhoff,[1]:211 Walter Cannon, Claude Shannon[1]:161
InfluencedNorbert Wiener, Ludwig von Bertalanffy, George Klir,[2] Herbert A. Simon, Klaus Krippendorff[3] Stafford Beer,[4] William T. Powers, Robert May[5] and Stuart Kauffman
W. Ross Ashby signature, Letter from Ashby to Jacques Riguet, dated 20 April 1953.svg
Ashby, c. 1924, aged about 21

W. Ross Ashby (6 September 1903 – 15 November 1972) was an English psychiatrist and a pioneer in cybernetics, the study of the science of communications and automatic control systems in both machines and living things. His first name was not used: he was known as Ross Ashby.

His two books, Design for a Brain and An Introduction to Cybernetics, were landmark works. They introduced exact and logical thinking into the brand new discipline of cybernetics and were highly influential.


William Ross Ashby was born in 1903 in London, where his father was working at an advertising agency.[6] From 1921 he studied at Sidney Sussex College, Cambridge, where he received his B.A. in 1924 and his M.B. and B.Ch. in 1928. From 1924 to 1928 he worked at the St. Bartholomew's Hospital in London. Later on he also received a Diploma in Psychological Medicine in 1931, and an M.A. 1930 and M.D. from Cambridge in 1935.

Ross Ashby started working in 1930 as a Clinical Psychiatrist in the London County Council. From 1936 until 1947 he was a Research Pathologist in the St Andrew's Hospital in Northampton in England. From 1945 to 1947 he served in India where he was a Major in the Royal Army Medical Corps.

When he returned to England, he served as Director of Research of the Barnwood House Hospital in Gloucester from 1947 until 1959. For a year, he was Director of the Burden Neurological Institute in Bristol. In 1960, he went to the United States and became Professor, Depts. of Biophysics and Electrical Engineering, University of Illinois at Urbana–Champaign, until his retirement in 1970.[7]

Ashby was president of the Society for General Systems Research from 1962 to 1964. After retiring in August of 1970, he became a Honorary Professorial Fellow at the University of Wales in 1970 and a fellow of the Royal College of Psychiatrists in 1971. In June of 1972 he was diagnosed with an inoperable brain tumor, and he died on 15 November.[6]

On 4–6 March 2004, a W. Ross Ashby centenary conference was held at the University of Illinois at Urbana–Champaign to mark the 100th anniversary of his birth. Presenters at the conference included Stuart Kauffman, Stephen Wolfram and George Klir.[8] In February 2009, a special issue of the International Journal of General Systems was specifically devoted to Ashby and his work, containing papers from leading scholars such as Klaus Krippendorff, Stuart Umpleby and Kevin Warwick.


Despite being widely influential within cybernetics, systems theory and, more recently, complex systems, Ashby is not as well known as many of the notable scientists his work influenced, including Herbert A. Simon, Norbert Wiener, Ludwig von Bertalanffy, Stafford Beer, Stanley Milgram, and Stuart Kauffman.[9] The realization that his work demanded publication, after many years of enjoying it as a private hobby, caused him great distress. Ashby consciously emulated Charles Darwin in the exposition of his work, and he found writing so difficult that he took correspondence courses in "Effective English and Personal Efficiency" to prepare to write his first book.[6]


Ashby kept a journal for over 44 years in which he recorded his ideas about new theories. He started May 1928, when he was medical student at St. Bartholomew's Hospital in London. Over the years, he wrote down a series of 25 volumes totaling 7,189 pages. In 2003, these journals were given to The British Library, London, and in 2008, they were made available online as The W. Ross Ashby Digital Archive.[10]


By 1941, Ashby had developed a coherent theory and wrote a 197 page booklet, titled "The Origin of Adaptation". This hand-written monograph was made publicly available in January 2021.[11] In it (p35), he expressed his opinion that "there is an abstract science of organisation, in the sense that there are laws, theories and discoveries to be made about organisation as such without asking what it is that is organised."


Ross Ashby was one of the original members of the Ratio Club, a small informal dining club of young psychologists, physiologists, mathematicians and engineers who met to discuss issues in cybernetics. The club was founded in 1949 by the neurologist John Bates and continued to meet until 1958.

The title of his book An Introduction to Cybernetics popularised the usage of the term 'cybernetics' to refer to self-regulating systems, originally coined by Norbert Wiener in Cybernetics: Or Control and Communication in the Animal and the Machine. The book dealt primarily with homeostatic processes within living organisms, rather than in an engineering or electronic context.

Earlier, in 1946, Alan Turing wrote a letter[12] to Ashby suggesting that Ashby use Turing's Automatic Computing Engine (ACE) for his experiments instead of building a special machine. In 1948, Ashby made the Homeostat.[13]

Ashby's 1964 paper Constraint Analysis of Many-Dimensional Relations began the study of reconstructability analysis, a multivariate systems modeling methodology based on set theory and information theory, which would later be developed by Klaus Krippendorff, George Klir, and others.[14]

In 1970, Ashby collaborated on simulation experiments regarding the stability of large interconnected systems.[15] This work inspired Robert May's groundbreaking studies of stability and complexity in model ecosystems.[5]


In An Introduction to Cybernetics, Ashby used set cardinality, or variety, as a measure of information. With this he formulated his Law of Requisite Variety stating that "only variety in [the regulator] can force down the variety due to [the source of disturbances]; only variety can destroy variety."[1]:207 This law can be applied for example to the number of bits necessary in a digital computer to assign unique labels to each state of a system.

In response, Conant (1970) produced his so-called "Good Regulator theorem" stating that "every good regulator of a system must be a model of that system".[16]

Stafford Beer applied variety to the practice of management, founding management cybernetics and developing the Viable System Model.[4]

A popular paraphrasing of the law is "only complexity absorbs complexity". However, while a web search reveals many attributions to Ashby, it appears such attribution is in error. The phrase is not listed by the Cybernetics Society.[17]

See also[edit]


Articles, a selection
  • 1940. "Adaptiveness and equilibrium". In: J. Ment. Sci. 86, 478.
  • 1945. "Effects of control on stability". In: Nature, London, 155, 242–243.
  • 1946. "The behavioural properties of systems in equilibrium". In: Amer. J. Psychol. 59, 682–686.
  • 1947. "Principles of the Self-Organizing Dynamic System". In: Journal of General Psychology (1947). volume 37, pages 125–128.
  • 1948. "The homeostat". In: Electron, 20, 380.
  • 1962. "Principles of the Self-Organizing System". In: Heinz Von Foerster and George W. Zopf, Jr. (eds.), Principles of Self-Organization (Sponsored by Information Systems Branch, US Office of Naval Research). Republished as a PDF in Emergence: Complexity and Organization (E:CO) Special Double Issue Vol. 6, Nos. 1–2 2004, pp. 102–126.
About W. Ross Ashby


The Papers of William Ross Ashby are housed at the British Library. The papers can be accessed through the British Library catalogue.[18]


  1. ^ a b c Ashby, William Ross (1956). An Introduction to Cybernetics (PDF). London: Chapman & Hall.
  2. ^ Conant, Roger (1981). Mechanisms of Intelligence: Ashby's Writings on Cybernetics. Seaside, California: Intersystems Publications. ISBN 1-127-19770-3.
  3. ^ Krippendorff, Klaus (1986). Information Theory: Structural Models for Qualitative Data. Newbury Park, California: SAGE Publications. p. 8. ISBN 0-8039-2132-2. "Finally, the work is unthinkable without W. Ross Ashby's early influence."
  4. ^ a b Beer, Stafford (1981). Brain of the Firm, 2nd Edition. West Sussex: John Wiley & Sons.
  5. ^ a b May, Robert M. (18 August 1972). "Will a Large Complex System be Stable?". Nature. 238 (5364): 413–414. Bibcode:1972Natur.238..413M. doi:10.1038/238413a0. PMID 4559589. S2CID 4262204.
  6. ^ a b c Biography of W. Ross Ashby The W. Ross Ashby Digital Archive, 2008.
  7. ^ Autobiographical summary, taken from Ashby's own notes, made about 1972.
  8. ^ W. Ross Ashby Centenary Conference The W. Ross Ashby Digital Archive, 2008
  9. ^ Cosma Shalizi, W. Ross Ashby web page, 1999.
  10. ^ W. Ross Ashby Journal (1928–1972) The W. Ross Ashby Digital Archive, 2008.
  11. ^ W.R. Ashby, "The Origin of Adaptation", 1941, British Library, London. Available online: W. Ross Ashby Digital Archive, 2021.
  12. ^ Alan Turing letter The W. Ross Ashby Digital Archive, 2008.
  13. ^ "Java applet simulation". Archived from the original on 2 August 2012. by Dr Horace Townsend
  14. ^ Zwick, Martin (2004). "An overview of reconstructability analysis" (PDF). Kybernetes. 33 (5/6): 877–905. doi:10.1108/03684920410533958.
  15. ^ Gardner, M. R.; Ashby, W. R. (1970). "Connectance of Large Dynamic (Cybernetic) Systems: Critical Values for Stability". Nature. 228 (5273): 748. doi:10.1038/228784a0. PMID 5472974.
  16. ^ Roger C. Conant and W. Ross Ashby, "Every good regulator of a system must be a model of that system", International Journal of Systems Science vol 1 (1970), 89–97.
  17. ^ "What Ashby Says..." Retrieved 16 May 2014.
  18. ^ William Ross Ashby Papers, archives and manuscripts catalogue, the British Library. Retrieved 02 June 2020

External links[edit]