This is another concept derived from Humberto Maturana. It is probably most simply understood initially in terms of two functional sub-systems who come to rely on each other for certain inputs. The unusual choice of image accompanying this piece is intended to convey the ongoing independence of each system. In no sense do the systems ‘merge’, nor does one become subordinate to the other. Luhmann gives the example of the structural coupling between the media and politics: ‘Politics benefits from “mentions” in the media and is simultaneously irritated by them. News reports in the media usually demand a response within the political system, and this response generally reappears in the media as commentary. So to a large extent the same communications have at once a political and a mass media relevance. But that only ever applies to isolated events and only ad hoc. This is because the further processing of communications takes a quite different route in the political system, especially where conditions of democracy and of opposition in the form of parties exist, from …