We develop a model of social choice over lotteries, where people's psychological characteristics are mutable, their preferences may be incomplete, and approximate interpersonal comparisons of well-being are possible. Formally, we suppose individual preferences are described by a...

Let X be a set of states, and let I be an infinite indexing set. Our first main result states that any separable, permutation-invariant preference order () on X^I admits an additive representation. That is: there exists a linearly ordered abelian group A and a `utility function' u:X--A such...