Symbolically generalized communication media, such as power, money, truth, etc., are called generalized because they can be used and reused by anyone. The media are accepted under the condition or trust that they can be reused. A person accepts a monetary payment because they expect to be able to use that money themselves. As Luhmann puts it,
[The] form in which the transaction is set is dissolved immediately afterward; for once in the hands of the recipient, the money is free for other combinations at will. No other medium attains this extension and this speed of dissolution and recombination, or loose and strict coupling. And it is hence understandable that money is often seen (notably by Parsons) as a model for an effectively symbolically generalized medium. (Theory of Society, vol. 1. p. 209)
When it comes to power, if someone carries out an order or instruction or submits to legitimate power, that’s only because she expects to be able to use power when she attains a similar position–or at least expects someone else to be able to use power on her behalf. In a republic, the party out of power, the opposition, accepts the government’s power because they want their own exercise power to be accepted when their turn comes. The generalized media don’t belong to anyone; they have to circulate. In terms of money, the political system even enforces this rule through taxation. To prevent you from saving all of your excess money, the state takes some of it away and puts it back in the economy.
This trait of communication media allows improbable communication to cross a threshold of probability. For instance, it is highly improbable that the party out of power would accept the power of the party in power (the government) if they didn’t expect to be able exercise power when their time came. The boundary between the two sides of the form has to be crossable. If the opposition expected to be permanently ruled or subordinated, they would probably revolt or just stop acquiescing to power. When people do revolt or riot, it’s because they don’t expect to ever have power in the current political system, which also implies that they don’t accept the legitimacy of the political system. They also tend to believe that the rules are enforced arbitrarily or unfairly or that they keep changing. The threat of negative sanctions or punishment is not enough to convince people to carry out orders or instructions that they don’t really want to carry out. They need to see power as legitimate.
It is the possibility of using negative sanctions that is the source of power. A negative sanction that is actually imposed decreases the stock of power. Power used indiscriminately or excessively loses it legitimacy. As Luhmann argued,
Precisely because it is not used and as long as it is not used, the possibility of imposing negative sanctions is a source of power. Power, therefore, comes to an end if the exercise of this possibility can be forced. (Politics and the Theory of the Welfare State, 158).
A negative sanction that is imposed (e.g., a prison sentence, job termination, slap on the face) is a form; the medial substratum, which is the storehouse of possible negative sanctions, coalesces into an actual negative sanction, which can then be resisted. The reactions to the punishment cannot be predicted. We could also call the medial substratum the virtual. It is surplus possibility.
On the level of language, a word is a medium because it can be reused. The medial substratum of words are phonemes, while the words are forms. The same limited list of phonemes are combined in different orders to make different words