Savage motivated his Sure-Thing Principle b y arguing that, whenever an act would be preferred if an event obtains and preferred if an event did not obtain, then it should be preferred overall. The idea that it should be possible to decompose and recompose decision problems in this way has...

We provide an axiomatization of an additively separable social welfare function in the context of Harsanyi’s impartial observer theorem. To do this, we reformulate Harsanyi’s setting to make the lotteries over the identities the observer may assume independent of the social alternative....