 The search for necessary and sufficient conditions for chaos presupposes that there is a clear-cut divide between chaotic and non-chaotic systems. EH may challenge this view, as every attempt to draw a line somewhere to demarcate the chaotic from non-chaotic systems is bound to be somewhat arbitrary. Ergodic systems are pretty regular, mixing systems are less regular and the higher positions in the hierarchy exhibit still more haphazard behaviour. But is there one particular point where the transition from ‘non-chaos’ to chaos takes place? Based on the argument that EH is a hierarchy of increasing degrees of randomness and degrees of randomness correspond to different degrees of unpredictability (see Section 5), Berkovitz, Frigg and Kronz (2006, Section 5.3) suggest that chaos may well be viewed as a matter of degree rather than an all-or-nothing affair. Bernoulli systems are very chaotic, K-systems are slightly less chaotic, SM-systems are still less chaotic, and ergodic systems are non-chaotic. This suggestion connects well with the idea that chaos is closely related to unpredictability.