Abstract
Standard state-space models, which are widely used in economics, preclude non-trivial forms of unawareness as shown by Dekel, Lipman and Rustichini (1998). We define a generalized state-space model that allows for unawareness. In order to facilitate applications we make no explicit use of modal syntax within the sematic model. Our model satisfies all "S4" properties as well as all desiderata on unawareness proposed by Modica and Rustichini (1999), Halpern (2001) as well as Dekel, Lipman and Rustichini (1998).