Sanctions can provide assurance to cooperative agents, not just deter egoists.

Evidence

Sen (1974: 78) writes: ‘A contract of mutual non-confession does not need any enforcement in the AG, whereas it is the crux of the matter in the PD.’ However, this is a little misleading. It is true that in AG the players share a first preference for a)bp. But, as indeed Sen says, they do both need assurance, and the prospect of the enforcement of a contract might be how the assurance was secured. This points up an important difference in the possible role of sanctions, a difference relevant to political theory. The addition of sanctions may change the utilities for a basically egoistic agent, or they may provide assurance for an agent who is basically cooperative. The latter, a very important possibility, is connected to a point I shall consider later: that the disposition to cooperation is typically cost sensitive. — Diego Gambetta, Trust - Making and Breaking Cooperative…, 104

Categorization

• DEEPTHINKING: Distinguishes two roles of sanctions — utility-shifting for egoists vs. assurance-providing for cooperators — which reframes the reader’s whole trust project: Hardin’s observable constraints may work by assurance, not deterrence. The cost-sensitivity of cooperation is a dense, nuance-rich idea.
• XREF: Directly feeds the reader’s Luhmann ‘familiarity’→trust distinction and Hardin’s ‘trust requires observable constraints on opportunistic behavior’ thesis. The assurance role of sanctions is precisely what collapses when sight vanishes in Saramago.
• SEED: Article angle: ‘Assurance vs. Deterrence’ — why sanctions that work by assuring the trustworthy are categorically different from sanctions that deter the egoistic, and what that means for why punishment-based social orders (like Saramago’s quarantine) fail to rebuild trust.