Critical instability
On the unrest that can precede a transition, and that may be a herald of change rather than a derailment.
Critical instability refers to the strong fluctuations that occur just before a system passes from one order to another. In the language of synergetics, they are the precursors of an order transition in self-organising processes.
When a system finds itself between two patterns, because the old order is losing its grip and the new one is not yet settled, an intermediate state arises that is marked by unrest and large fluctuations. Chance and unpredictability then play a large role. Two kinds of transition are distinguished: transitions in which order arises out of disorder, and transitions between different forms of dynamic order. In both cases it is precisely these critical fluctuations that announce the transition.
Unrest as a possible turning point
For clinical practice this is an important and hopeful insight. An increase in fluctuations, for example in a patient who becomes more changeable and whose mood and complaints swing back and forth more strongly, need not be a sign of deterioration. Put cautiously, it may instead be a herald of an approaching reordering. Schiepek and colleagues have shown that such critical fluctuations can be measured in the course of therapy and often precede a meaningful change.
This connects with the early warning signals discussed elsewhere in this lexicon. It asks of the clinician a certain tolerance for unrest: not every increase in instability needs to be damped straight away. Sometimes bearing a phase in which the outcome is still open is precisely the condition under which something new can arise.