Impartial observer theorem with ambiguity

This paper revisits the debate between Harsanyi and Rawls on collective decision-making with impartiality (Veil of Ignorance), focusing on how different levels of uncertainty influence the resulting social welfare functions. By incorporating ambiguity into the Impartial Observer framework, the paper constructs a continuum of compromise positions between Harsanyi’s utilitarian approach and Rawls’s maximin rule. In the proposed model, the independence between the uncertainty faced by the Impartial Observer over the distributions of identities and the uncertainty faced by each individual over the distributions of outcomes allows us to introduce ambiguity on both identity acts and/or outcome acts to explore various configurations where the Impartial Observer’s preference representation changes based on the type and level of uncertainty considered. The results offer a more nuanced understanding of impartiality in social choice contexts and help clarify the philosophical foundations of the Harsanyi–Rawls debate.