 Not only bimodal, but multimodal (also called polymodal) logics, are standard in the literature: a typical case is the logic of knowledge (or epistemic logic), usually endowed with modal operators \(K_{1},K_{2},\ldots,K_{m}\) representing the knowledge of \(m\) agents (or “knowers”). The formula \(K_{i}\alpha\) means “agent \(i\) knows \(\alpha\)”, and the language is able to express, for instance, “\(i\) knows that \(j\) does not know that \(i\) knows \(p\)” by means of \(K_{i}\neg K_{j}K_{i}p\). No additional mixing principles are mandatory for the combined logic of many agents, but bridge axioms may, of course, be added.