Organization presupposes that the role of membership in the system is contingent, i.e. that a non-member could become a member but also that members could become non-members, in other words, that there is a recruitment pool of possible members and that it is possible for members themselves to leave or be dismissed. This is one area of contingency. The other lies in the rules which constitute the role of the member and the rules which are designed to determine conduct in organizations. These rules too are defined contingently; they are positive in the sense that they are based on decisions and are, through this mode of validity, in regard to origin or their changeability, or by a comparison with systems in the environment, seen as contingent. These two areas of contingency can now support one another and foster one another to the extent that both become prominent and distinctive.

Niklas Luhmann, Trust and Power, loc. 781