 A situation is a partial state the world might be in: something like \(a\) being \(F\). Situations are classified by what are called situation types. A proposition involves classifying a situation as being of a situation type. Thus, a proposition \(\{s\); [\(\sigma]\}\) tell us that situation \(s\) is of type \(\sigma\). The situation \(s\) here plays a number of roles, including that of providing a context.