Substantive assumptions in interaction: a logical perspective

In this paper we study substantive assumptions in social interaction. By substantive assumptions we mean contingent assumptions about what the players know and believe about each other’s choices and information. We explain why such assumptions are important, we show how to identify and compare them, formally, and we also show that there exist contexts where no substantive assumptions are being made. Towards the end of the paper we briefly explain the relation between such structures and a number of other “large” structures studied in epistemic game theory.