Utility functions embodying nonpaternalistic altruism can be regarded as being generated through social interactions among altruistic individuals. As such, they show an important interdependence. Assuming linear altruism, the paper obtains the following results. First, nonpaternalistic altruism has a tendency to unify utility functions. Second, by linearly extrapolating a given structure of altruistic interactions, one can ascertain the extent to which the unification can proceed and its direction. Third, the unification implies narrowing down of the range of conflicting choices but the direction of unification lacks ethical principles. Fourth, the conditions utilitarianism imposes on the structure of altruistic interactions are characterized.