L.von BERTALANFFY writes: "ASHBY's model for adaptiveness is, roughly that of step functions defining a system, that is, functions which, after a certain critical value is overstepped, jump into a new family of differential equations. This means that, having passed a critical point on its trajectory, the system starts off in a new way of behavior. Thus, by means of step functions, the system shows adaptive behavior by what the biologist would call trial and error: it tries different ways and means, and eventually settles down in a field where it does not come anymore in conflict with critical values of the environment"(1956, p.7).

ASHBY's homeostat is an electromagnetic model of this adaptation mode.

The adaptive capacity of any system thus depends on the existence, at least potentially, of this type of step functions. This model can be usefully compared with other concepts related to adaptation: Requisite variety, Hypercycle, Organizational closure, Catastrophes, Bifurcation, Stability in topological terms, etcâ€¦