A Note on Unawareness

Modica and Rustichini 1994] provided a logic for reasoning about knowledge where agents may be unaware of certain propositions. However, their original approach had the unpleasant property that nontrivial unawareness was incompatible with partitional information structures. More recently, Modica and Rustichini 1999] have provided an approach that allows for nontrivial unawareness in parti-tional information structures. Here it is shown that their approach can be viewed as a special case of a general approach to unawareness considered by Fagin and Halpern 1988].