…All this is mistaken. What the system really needs, and all it needs, is a way of measuring it’s own internal tendency to depart from stability, and a set of rules for experimenting with responses, which will tend back to an internal equilibrium. Then there is no need to know in advance what might cause a disturbance; there is no need to know what has caused a disturbance. To be aware of something happening and label it disturbance, and to be able to alter internal states until the effects of the disturbance are offset, is enough.