Contradictions, Disagreement and Normative Error

My aim is to discuss some counterexamples to the following principle: (P) Necessarily, for every proposition p, for every cognitive agent S and for every cognitive agent S*, if S believes that p and S* believes that ¬p, then either S makes a normative error or S* makes a normative error. If we assume the identity between S and S*, then (P) regulates what I'm going to call psychological contradiction; conversely, if we assume the non-identity between S and S*, then (P) regulates cases of disagreement. In trying to offer counterexamples, I will compare two different approaches: a three-valued approach and a relativist approach. I will argue that adopting the latter is preferable, since, contrary to the former, in offering counterexamples to (P) it does not commit us to hold the controversial metaphysical views that I will present in section 2. Furthermore, it allows us to propose genuine counterexamples not only in cases of syntactic disagreement, but also in cases of semantic and ontological disagreement.