The concept of complexity has therefore to be defined in very abstract terms. This can be done straightforwardly in terms of a distinction between system and environment and in terms of a system’s potential for actualization. The concept then signifies a number of possibilities which are opened up through system formation. It implies that the conditions (and hence boundaries) of possibility can be specified, that the world becomes constituted after this fashion and also that it contains more possibilities than can be realized, so that in this sense it has an 'open' structure. From one angle this relationship between world and system can be seen as a problem of overload and of a constantly threatened stability. This, in fact, is the approach of functionalist systems theory. From the opposite perspective, the same situation appears as a 'higher' order, constructed by reducing complexity through system building, which renders the problem one of selection. This latter approach is that of cybernetic systems theory.

DEFINE: Luhmann defines complexity abstractly as a surplus of possibilities over what a formed system can actualize, distinguishing overload-oriented functionalism from selection-oriented cybernetics.

Niklas Luhmann, Trust and Power, loc. 101