Hence, given the condition that enough people are trustworthy, Luhmann's theory is a functional explanation in the demanding sense of this paradigm. What does this tell us? It does not say that because trust is functional it will happen. Rather, it says that if the causal chain producing trust ever gets under way, it will tend to be sustained by the feedback mechanism of the explanation. That fact raises an additional question. How does the causal chain get under way? If others are generally untrustworthy, we can generally expect everyone to learn not to be readily open to cooperative gestures. We could imagine that trusting would be a result of social evolution from a prior, less complex world in which ongoing interactions are dense enough to ground trust, as in the thick-relationships variant of trust.

XREF: Connects to Luhmann's broader systems theory and evolutionary accounts of social trust, as well as Putnam's social capital literature on dense networks fostering trust.

Russell Hardin, Trust and Trustworthiness, loc. 673