Motivating inferentialism

Robert Brandom has supported his inferentialist conception of semantic content by appealing to the claim that it is a necessary condition on having a propositional attitude that one appreciate the inferential relations it stands in. When we see what considerations can be given in support of that claim, however, we see that it doesn’t even motivate an inferentialist semantics. The problem is that that claim about what it takes to have a propositional attitude does nothing to show that its inferential relations are a feature of its content rather than of the relation that the subject stands in to that content—that is, the attitude.