2. The standard definition of Bayesian Nash equilibrium is deceivingly simple it hides a whole infinite hierarchy of implicit assumptions about higher-order beliefs It is not my objective to argue whether or not these assumptions are reasonable. Rather I wish to emphasize that, just because they are not apparent in Definition 2(or in any textbook definition of Bayes Nash equilibrium, for that matter), one should not conclude that these assumptions are not necessary! On the other hand, one should not assume that these assumptions are the only ones consistent with Bayesian Nash equilibrium analysis. In fact, relaxing them leads to interesting modelling possibilities-as I shall illustrate in the next lecture2. The standard definition of Bayesian Nash equilibrium is deceivingly simple: it hides a whole infinite hierarchy of implicit assumptions about higher-order beliefs. It is not my objective to argue whether or not these assumptions are reasonable. Rather, I wish to emphasize that, just because they are not apparent in Definition 2 (or in any textbook definition of Bayes Nash equilibrium, for that matter), one should not conclude that these assumptions are not necessary! On the other hand, one should not assume that these assumptions are the only ones consistent with Bayesian Nash equilibrium analysis. In fact, relaxing them leads to interesting modelling possibilities—as I shall illustrate in the next lecture. 6