is a terminus technicus of sociological systems theory coined by Luhmann.
It owes its existence to an interpretation of Spencer Brown's concept of Form, whose fundamental innovation consists in having brought together the two traditions of thinking about (and: by means of) forms and distinctions in a "simple formula" (Klinger 2011, 133): Distinction is form.
Spencer-Brown states the basic ideas and terminological prerequisites for the construction of concepts in general, and the construction of the two-sided form in particular, in the introductory sentences of the main text of the Laws of Form (1979, 1):
> We take as given the idea of distinction and the idea of indication, and that we cannot make an indication without drawing a distinction. We take, therefore, the form of distinction for the form.
From the definition/ideas difference (i.e. the definition in the context of ideas), the general 'blueprint' of the system-theoretical two-sided form can now be inferred (cf. also Karafillidis 2010, 81), which is often given in the form of an enumeration of its elements:
> „Nenne Form im Anschluss an Spencer-Brown (a) die Innenseite einer Unterscheidung zusammen mit (b) ihrer Außenseiten (c) der Teilung zwischen den beiden Seiten und (d) dem Raum, der von der Unterscheidung hervorgerufen und in Anspruch genommen wird.“
"Call form, following Spencer-Brown, (a) the inside of a distinction together with (b) its outside (c) the division between the two sides and (d) the space evoked and occupied by the distinction." (Baecker 2013, 17)
According to this common interpretation (see also Simon 2018), the two sides of the two-sided form are defined as "inner side" and "outer side", which are referred to their places by a Boundary, in a space that is spanned by the distinction and designation of one of the two sides. It is this version of the concept of form to which the characteristic form figures discussed in this article are related. They are formed by replacing the letters that can be written under or next to the cross-hooks (also called "Quere") in the Laws of Form with normal language words. The forms or arrangements of forms obtained in this way partly reproduce exemplary formulas of the Laws of Form, but complex – even "crooked" (Baecker 2021) – form notations are also common, which have emancipated themselves from the formulas introduced in the Laws of Form and seem to go their own way in a way that has yet to be investigated.
Without going into questions of the meaning of these notations at this point, it can be said that the mere writing of such forms does not necessarily invoke the entire mathematical apparatus of the Laws of Form, just as the mere occurrence of algebraic symbols in an expression does not already make it an expression of algebra.
In this meaning, one can describe the form of the system in normal language as the reproduction of the distinction between system and environment, but one can also describe this form by means of the barre oblique – "system/environment" – or with the querene notation of the Laws of Form (Fig. 1):
Fig. 1
However, depending on how closely one wishes to orient oneself not to the concept of form, but to the calculus of forms of the Laws of Form, the question may play a role as to what extent this equipping of the form with words is in accordance with the rules of the Laws of Form.
Does this equipping only accomplish what is already laid out in the primary algebra of the Laws of Form, insofar as the letters of the primary or extended algebra are replaced by names?
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