  Morris (1996, 1997) introduced preference-based definitions of knowledge and
belief in standard state-space structures. This paper extends this
preference-based approach to unawareness structures (Heifetz, Meier, and
Schipper, 2006, 2008). By defining unawareness and knowledge in terms of
preferences over acts in unawareness structures and showing their equivalence
to the epistemic notions of unawareness and knowledge, we try to build a bridge
between decision theory and epistemic logic. Unawareness of an event is
characterized behaviorally as the event being null and its negation being null.
