Cooperation only becomes a theoretical puzzle when one party depends on another.

Evidence

Under this definition, a situation in which two agents cooperate necessarily involves at least one of them depending on the other, or being, as I shall also put it, a dependent party. There are, of course, ventures that would naturally be called ‘cooperation’ but do not fall under this definition, because everyone in them is under the immediate control of everyone: if a party does not do his bit, this can be immediately detected. These are of no interest to the present discussion, which entirely concerns cases in which one party depends on another. — Diego Gambetta, Trust - Making and Breaking Cooperative…, 151

Categorization

• XREF: This distinction between symmetric observability and asymmetric dependence is exactly the substrate Saramago removes in Blindness — sightedness collapses mutual control into one-directional dependence. Directly connects to the reader’s Hardin point that trust requires observable constraints.
• DEFINE: Defines the operative sense of ‘cooperation’ for the Luhmann/Hardin synthesis: ventures where at least one party depends on the other, because full mutual observability is absent.