Tyler Burge has in many writings distinguished between mental content externalism based on incorrect understanding and mental content externalism based on partial but not incorrect understanding. Both and have far-reaching implications for analyses of communication and concept possession in various expert-layperson relations, but Burge and his critics have mainly focused on . This article first argues that escapes the most influential objection to . I then raise an objection against Burge’s argument for . The objection focuses on Burge’s claim that (...) a person with a partial understanding of a term in our community expresses our standard concept because he is willing to defer to our standard understanding, while his “Putnamian” twin in a counterfactual community does not. The problem with Burge’s argument for this claim is that he does not consider the possibility that the person in our community and the twin would defer to the same understanding if they were presented with the same alternatives. Drawing from widespread dispositional assumptions about meaning, I argue that Burge must accept that they express the same concept if they would defer to the same understanding. The article closes with an examination on various ways the externalist may attempt to avoid this problem and concludes that none of them succeeds. (shrink)