 To handle the second kind of case, Briggs (2012) defines a relation of exact equivalence among Boolean propositions using the state space semantics of Fine (2012). Within a world, the state that makes a proposition true is the collection of values of variables that contribute to the truth of the proposition. In our example world, the state that makes Gas level = 3 true is the valuation Gas level = 3. By contrast, the state that makes 