**:** Bar-Yam Y
**:** Multiscale Variety in Complex Systems

**:**
**:** 2004
** :**
** :** Complexity

** () :** 4
**:** 9

** :** Bar-Yam Y. Multiscale Variety in Complex Systems // Complexity. 2004. Vol. 9. No 4. P. 37 45.

**:** The Law of Requisite Variety is a mathematical theorem relating the number of control states of a system to the

number of variations in control that is necessary for effective response. The Law of Requisite Variety does not

consider the components of a system and how they must act together to respond effectively. Here we consider the

additional requirement of scale of response and the effect of coordinated versus uncoordinated response as a key

attribute of complex systems. The components of a system perform a task, with a number of such components

needed to act in concert to perform subtasks. We apply the resulting generalizationa Multiscale Law of

Requisite Varietyto understanding effective function of complex biological and social systems. This allows us

to formalize an understanding of the limitations of hierarchical control structures and the inadequacy of central

control and planning in the solution of many complex social problems and the functioning of complex social

organizations, e.g., the military, healthcare, and education systems.

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