Widely-Known Systems Laws, Principles, Theorems and Hypotheses
The second law of thermodynamics: In any closed system the amount of order can never increase, only decrease over time.
The complementary law: Any two different perspectives (or models) about a system will reveal truths regarding that system that are neither entirely independent nor entirely compatible (Weinberg 1975)
The law of requisite variety: Control can be obtained only if the variety of the controller is at least as great as the variety of the situation to be controlled (Ashby 1964).
The law of requisite hierarchy: The weaker and the more uncertain the regulatory capability, the more hierarchy is needed in the organisation of regulation and control to get the same result (Aulin &Ahmavaara).