Updating on the evidence of others

One often learns the opinions of others without getting to hear the evidence behind them. How should you revise your own opinions in such cases? Dietrich (2010) shows that, for opinions about objective chance, the method known as upco effectively adds your interlocutor’s evidence to your own. We provide a simple way of viewing upco that makes properties like Dietrich’s easy to appreciate, and we do three things with it. First, we unify Dietrich’s motivation for upco with another motivation due to Easwaran et al. (2016). Second, we show that laypeople can sometimes use upco to resolve expert disagreements. And third, we use it to cricitize the social argument for the uniqueness thesis.