Article,
Requisite variety and its implications for the control of complex systems
Cybernetica, 1 (2): 83--99 (1958)
Abstract
Recent work on the fundamental processes of regulation in biology
(Ashby, 1956) has shown the importance of a certain quantitative
relation called the law of requisite variety. After this relation
had been found, we appreciated that it was related to a theorem in
a world far removed from the biological—that of Shannon on the quantity
of noise or error that could be removed through a correction-channel
(Shannon and Weaver, 1949; theorem 10). In this paper I propose to
show the relationship between the two theorems, and to indicate something
of their implications for regulation, in the cybernetic sense, when
the system to be regulated is extremely complex.
Since the law of requisite variety uses concepts more primitive than
those used by entropy, I will start by giving an account of that
law.
