Order parameter
The quantity that describes the behaviour of the whole — and in turn marshals the parts.
An order parameter is a measure or concept that allows the global behaviour of a system of many components or subsystems to be captured in a single quantity. Where the individual parts each seem to go their own way, the order parameter describes the pattern they form together.
The notion comes from Hermann Haken's synergetics. What makes it remarkable is the twofold direction in which it works. On the one hand the order parameter arises from the interaction of the many parts — it emerges from below. On the other, once it has arisen it begins to constrain and steer the behaviour of those same parts; Haken spoke of enslaving, the marshalling of the components by the very pattern they have brought forth. Between the small and the large there is thus a circular causality: bottom-up and top-down at once.
In psychotherapy
In the work of Günter Schiepek the order parameter of a therapeutic process is not a single measurement but a pattern — an interplay of complaints, meanings, relationships and behaviour that, taken as a whole, has a direction. Such a pattern can be recognised, in his view, by the coherence it shows over time: mood, self-image, sleep and activity do not move independently, but as facets of one underlying order.
The practical value is that, by following the order parameter, one need not steer on isolated symptoms but on the pattern that carries them. If the order parameter changes, the system shifts as a whole — sometimes gradually, sometimes in a leap. Put cautiously, the concept thereby offers a language for what clinicians often sense intuitively: that beneath the multiplicity of complaints a single movement is at work.