William Ross Ashby

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W. Ross Ashby
Born (1903-09-06)6 September 1903
London, England
Died 15 November 1972(1972-11-15) (aged 69)
Fields Psychiatry, Cybernetics, Systems theory
Known for Cybernetics, Law of Requisite Variety, Principle of Self-Organization
Influenced Norbert Wiener, Ludwig von Bertalanffy, Herbert A. Simon, Stafford Beer, Walter Cannon and Stuart Kauffman

W. Ross Ashby (London, 6 September 1903 – 15 November 1972) was an English psychiatrist and a pioneer in cybernetics, the study of complex systems. 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 nascent discipline and were highly influential.


William Ross Ashby was born in 1903 in London, where his father was working at an advertising agency.[1] From 1917 to 1921, William studied at the Edinburgh Academy in Scotland, and from 1921 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.[2]

Ashby was president of the Society for General Systems Research from 1962 to 1964. He became a fellow of the Royal College of Psychiatry in 1971.

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.[3] 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.[4]


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, Kevin Warwick, and Stuart Kauffman.[5]


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 totalling 7,400 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.[6]


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[7] 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.[8]


In An Introduction to Cybernetics, Ashby formulated his Law of Requisite Variety[9] stating that "variety absorbs variety, defines the minimum number of states necessary for a controller to control a system of a given number of states." This law can be applied for example to the number of bits necessary in a digital computer to produce a required description or model.

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".[10]

Stafford Beer applied Variety to found management cybernetics and the Viable System Model. Working independently, Gregory Chaitin followed this with algorithmic information theory.

A popular paraphrasing of the law is "only complexity absorbs complexity", yet 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.[11]

See also


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


  1. Biography of W. Ross Ashby The W. Ross Ashby Digital Archive, 2008.
  2. Autobiographical summary, taken from Ashby's own notes, made about 1972.
  3. W. Ross Ashby Centenary Conference The W. Ross Ashby Digital Archive, 2008
  4. International Journal of General Systems
  5. Cosma Shalizi, W. Ross Ashby web page, 1999.
  6. W. Ross Ashby Journal (1928–1972) The W. Ross Ashby Digital Archive, 2008.
  7. Alan Turing letter The W. Ross Ashby Digital Archive, 2008.
  8. "Java applet simulation". Archived from the original on 2 August 2012.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles> by Dr Horace Townsend[dead link]
  9. WR Ashby, "An introduction to cybernetics", London, Chapman & Hall,1956. [1]
  10. Int. J. Systems Sci., 1970. vol 1, No. 2 pp89-97
  11. "What Ashby Says..." Retrieved 16 May 2014.

External links