  We initiate the study of voting rules for participatory budgeting using the
so-called epistemic approach, where one interprets votes as noisy reflections
of some ground truth regarding the objectively best set of projects to fund.
Using this approach, we first show that both the most studied rules in the
literature and the most widely used rule in practice cannot be justified on
epistemic grounds: they cannot be interpreted as maximum likelihood estimators,
whatever assumptions we make about the accuracy of voters. Focusing then on
welfare-maximising rules, we obtain both positive and negative results
regarding epistemic guarantees.
