A possible reply to the criticism of the infinitary nature of the common belief assumption is that the result should be seen as the analysis of a benchmark case, rather than a description of genuine game playing situations or a prescription for what rational players should do (Aumann 2010). Indeed, common knowledge/belief of rationality has long been used as an informal explanation of the idealizations underlying classical game-theoretical analyses (Myerson 1991). The results above show that, once formalized, this assumption does indeed lead to a classical solution concept, although, interestingly, not the well-known Nash equilibrium, as is often informally claimed in early game-theoretic literature. Epistemic conditions for Nash equilibrium are presented in Section 5.1.