 More precisely, Roemer recommends a socialist model of cooperation that he calls “Kantian optimisation”. Kantian optimisation challenges both the standard economic picture of individuals as utility maximisers, and in the standard ways in which that standard picture is adjusted for other-regarding motivations (Roemer rejects the idea that Nash optimisation is the uniquely rational way to optimise). In Kantian optimisation, individuals choose the action that maximises their payoff, assuming that all other agents take the same action. Very roughly, cooperation depends, not on altruism (which is implausibly demanding), but on solidarity (the idea that we are “all in the same boat”) and trust (the idea that if we take the cooperative action, enough others will do so as well). This socialist model of cooperation is said to be realistic, in that it respects certain behavioural results in both the laboratory and real life (recycling and tipping, for instance (Roemer 2019a: 14–16)).