Abstract

Gauthier and Hobbes reduce Prisoners Dilemmas to co-ordination problems (CPs). Many think rational, face-to-face agents can solve any CP by agreed fiat. But though an agent can rationally use a symmetry-breaking technique (ST) to decide between equal options, groups cannot unless their members' STs luckily converge. Failing this, the CP is escapable only by one agent's non-rational stubbornness, or by the group's "conquest" by an outside force. Implications: one's strategic rationality is group-relative; there are some optimums groups in principle cannot rationally choose; thus justice cannot always be a rationally contracted optimum. Howard Sobel provides the point of departure.