Any regulator that is maximally successful and simple must be isomorphic with the system being regulated. This makes a model necessary. With regard to the brain, insofar as it is successful and efficient as a regulator for survival, it must proceed, in learning, by the formation of a model (or models) of its environment.
The theorem does not explain what it takes for the system to become a good regulator. The problem of creation of good regulators is addressed by practopoietic theory.
- Conant and Ashby, Int. J. Systems Sci., 1970, vol 1, No 2, pp. 89–97