Ashby's Law of Requisite Variety
Law of Requisite Variety
The notion that the degree of control of a system is proportional to the amount of information available. In other words, one needs an appropriate amount of information to control any system, whatever it is.
Origin
British cybernetician W. Ross Ashby formulated the law of requisite variety in his 1956 book An Introduction to Cybernetics, considered the first textbook on cybernetics. The law states that "only variety can absorb variety"—regulation is possible only if the regulating system is as various and flexible as the system to be regulated. More formally, a regulator's capacity cannot exceed its capacity as a channel of communication. This principle became a central law for understanding the proper functioning of mechanical and biological entities.