There remains the zone of free-floating social relationships formed by choice in the expectation of mutuality. The most neutral term for this zone is association, but its strongest form of expression is friendship, the negotiated order of free individuals joined by affection and shared experience rather than by legal sanction or the ties of blood. It is in this third area of social life that trust plays so prominent a role, relatively unmediated by the formal obligations of kinship and contract.

Diego Gambetta, Trust - Making and Breaking…, loc. 2310