Chapter 4 Possibility and probability: Value, conflict and choice

Consider now the set of all possible events that can occur in a given context. There is a distinction between an elementary event and a compound event. The set of elementary events is exhaustive, exclusive and elementary: the elementary events cover all the possible events; no two of them can occur at the same time; and all other events are constituted by compounds of these. Denoting the set of all elementary events by E, the set of all (possibly compound) events is the power set of E, S^E. The set of events, S^E, consists of pairs of events: for each event e there is its complementary event not-e; and for the event not-e there is its complementary event not-(not-e)=e. In any given world only one event of any complementary pair can occur.