Would a fully rational actor need to have a universal prior? Wouldn’t they need to have justified one choice of a universal prior over all others? It seems like there might be a hard first step here that could prevent them from committing to a single joint probability distribution. Maybe you’d want a prior over universal priors, but then where would that come from?
I’d usually think of being fully rational as giving constraints after your choice of prior; there are questions about whether some priors are better than others, but you can treat that separately.
I’d usually think of being fully rational as giving constraints after your choice of prior; there are questions about whether some priors are better than others, but you can treat that separately.