 To make things more concrete let us assume that contexts are sets of possible worlds and that an update \(C[S]\) of \(C\) with a simple clause \(S\) is \(C\cap p\), where \(p\) is the propositional content of \(S\): updating \(C\) with a clause outputs the \(C\) worlds in which the clause is true. The rules in  (18)  show a Heimian fragment of a dynamic interpretation of the main propositional operators in English.