A resilient system, or, organisation is able to withstand the effects of stress and strain and to recover from adverse conditions over long time periods. One way of describing that is to think of a system as being in one of several states, where a state can be defined as ‘any well-defined condition or property that can be recognised if it occurs again’ (Ashby, 1956, p. 25). The set of possible states constitutes the so-called state space, and each state has a set of associated conditions that specify whether the system changes to another state. The state space description is ubiquitous and can be applied to almost any type of system. The simplest possible case is, of course, a system that can be in either of two states or conditions. This applies to an uncomplicated device such as an electrical switch, which can be either ‘on’ or ‘off’, but also to a complex system such as a national economy that can be either growing or receding. A car engine might be described by means of three states, namely ‘stopped’, ‘idle’, or ‘running’. Even a mighty nation can – from one perspective – be characterised as being in one of five states according to the threat condition, such as ‘green: low’, ‘blue: guarded’, ‘yellow: elevated’, ‘orange: high’, and ‘red: severe’.