 One can take a doxastic relational model with its relation \(R_B\) being serial, transitive and Euclidean (a KD45 setting), and use a modality B semantically interpreted with respect to \(R_B\) in the standard way. In this setting, two options arise. The first one is syntactic, as in the examples that have been discussed so far, and consists in defining a modality for knowledge as ‘true belief’: \(K'\varphi := B\varphi \land \varphi\). The second is semantic, and consists in defining an epistemic equivalence relation \(R_K\) as the reflexive and symmetric closure of the doxastic relation, then using it in the standard way to give the semantic interpretation of a modality K.