  We show that the knowledge of an agent carrying non-trivial unawareness
violates the standard property of 'necessitation', therefore necessitation
cannot be used to refute the standard state-space model. A revised version of
necessitation preserves non-trivial unawareness and solves the classical
Dekel-Lipman-Rustichini result. We propose a generalised knowledge operator
consistent with the standard state-space model of unawareness, including the
model of infinite state-space.
