 When it comes to the Liar, Barwise and Etchemendy construe Liar propositions as having the form \(f_s = \{s\); [\(\Tr,f_s\); 0]\(\}\), relative to an initial situation \(s\). This is a proposition \(f_s\) which says of itself that its falsity is a fact that holds in \(s\). (In Barwise and Etchemendy’s notation, the 0 indicates falsity, so the situation type is that the state of affairs of the proposition being false holds. The proposition says this is a fact that holds in \(s\).) There is a sense in which this proposition cannot be expressed. In particular, the state of affairs \(\langle \Tr,f_s\); \(0\rangle\) cannot be in \(s\). (Actually, Barwise and Etchemendy say that the proposition is expressible, but give up on what they call the \(F\)-closure of \(s\). But there is a core observation in common between these two points, and the details do not matter for our purposes here.) There is then a distinct situation \(s' = s \cup \{\langle \Tr,f_s\); \(0\rangle \}\), and the proposition \(\{s'\); [\(\Tr,f_s\); 0]\(\}\) relative to this new situation—this new ‘context’—is true.