Before revision:  To explicitly formalize these attitudes , we employ tools from interactive epistemology, by defining the corresponding epistemic events in epistemic possibility structures, which are the counterpart of epistemic type structures suited for our analysis in the presence of ignorance, We show that the behavioral implications related to common belief in these events have algorithmic counterparts in terms of iterative deletion procedures. While optimism is related to Point Rationalizability, to capture pessimism we introduce a new algorithm , deemed Wald Rationalizability .
After revision:  To explicitly formalize these attitudes , we employ tools from interactive epistemology, by defining the corresponding epistemic events in epistemic possibility structures, which are the counterpart of epistemic type structures suited for our analysis in the presence of ignorance, We show that the behavioral implications related to common belief in these events : while optimism is related to Point Rationalizability, to capture pessimism we introduce a new algorithm , deemed Wald Rationalizability .