  I here propose to do something a little different, namely to employ the ordinary propositional variables ‘\(p\)’, ‘\(q\)’, ‘\(r\)’ etc., for ‘propositions’ in the Diodoran sense [i.e. propositions which ‘may be true at one time and false at another’] and to use certain operators which take such propositions as arguments, and which form functions taking such propositions as values. I shall use ‘\(Fp\)’ for ‘It will be the case that \(p\)’. (1955b: 205.)