The concepts of ego and alter should leave open whether they concern psychic or social systems . . . (Social Systems, p. 106)
When Luhmann refers to ego and alter, as in discussions of double contingency, it is easy to assume that he means psychic systems as in interaction systems of two people. But ego and alter also refer to other kinds of social systems, including function systems and organizations. So in the structural coupling or irritation (perturbation, resonance) between economy and politics, these systems can be considered ego and alter. The communication events that occur within each system are doubly contingent. In other words these two function systems are “black boxes” to each other, just as two psychic systems are black boxed to each other. The economy cannot know what is happening in the political system, and vice-versa, just as one person cannot know what another person is thinking or feeling. Each system just make guesses about what is going on in the other system.
Earlier in Social Systems, Luhmann writes,
The social dimension concerns what one at any time accepts as like oneself, as “alter ego” . . . (80)
All one system can do is assume that another system is like itself. So I assume that sitting next to me on a park bench can see and hear what I am seeing and hearing. I assume that we are perceiving the same world. Thus we can communicate even though we do not perceive exactly the same world.
In an interaction system, such as a conversation between two people, the system (not each psychic system separately) selects meanings from a horizon of possible meanings. Each communicative event, which passes away in the same moment is emerges, must serve as the premise for the next event if the system is to continue its autopoiesis.
The ego-alter concept can be confusing, however, because two psychic system can come together, so to speak, to produce an interaction system. A new system emerges as communication. This might lead to the conclusion that a third system, the interaction system, emerges between the two psychic systems and that the two psychic systems somehow share this interaction system.
But if two function systems, such as politics and economy, mutually irritate each other, a third system does not emerge between the two because that would require a mixture of codes. But in an interaction system, a new system does not exactly emerge between two psychic systems either. The interaction system exists in the environment of the psychic systems, and each psychic system has its own (unshared) environment. Any change that occurs in the thinking or feeling of a psychic system during communication only happens in that psychic system, not in the interaction system (because interactions systems do not think or feel; they communicate). Similarly, any change that occurs in the economy or the political system occurs only within the respective systems, not somewhere in-between the two systems. There is nothing shared or experienced in common between the two systems.
Anything said to exist in-between could only be observed by a third. This might be the liminal space discusseded by Paul Stenner.