Are the semantic truths a priori entailed by the non-semantic truths? More precisely, let P be a statement of all positive microphysical truths about the world, let Q be a statement of all phenomenological truths, let T be a ‘that’s all’ statement, let I be an indexical marker: are the semantic truths entailed by PQTI together with a priori truths?

A profitable way to investigate this question is to consider a case of radical interpretation in which a ‘mighty knower’ proceeds from omniscience about PQTI to omniscience about the semantic truths. That is, if we let X be a set of interpretations, the mighty knower needs to select a ‘winner’ from X, on the basis of knowledge of PQTI and a priori truths alone. The task can only be successfully completed if there are some a priori sufficient conditions on her choice of an interpretation which, given PQTI deem the intended interpretation the winner. Many such constraints have been suggested in the literature: the principle of charity, humanity, knowledge, eligibility, and causal adequacy, to name a few. Taken individually, these seem to fall prey to the ‘bizarre interpretation problem’ – that is, they induce ties between the intended interpretation and bizarre ones, and hence fail to deem the intended interpretation the winner.

Thus, several philosophers suggest that some combination of constraints a priori entail the semantic truths. The thought is that the mighty knower is rational to select the interpretation that is in some sense best overall, in that it provides the best balance or best fit in relation to a number of factors. As has been widely noted, there is no guarantee that this will work. I would like to be able to go further and argue that it can’t work. I will suggest (at this stage in a highly tentative and exploratory way) that we might be able to appeal to some of the machinery of social choice theory to show that there is no rational method for determining an overall best fit. The intuitive reason is that the different factors—such as charity and eligibility, for instance—cannot be traded off against one another, because they are incomparable.