 A posssible way out of this dilemma is to choose the alternative procedure sketched above (at the end of section 3.6) by taking these logical properties primarily to be properties of propositional forms. Thereby the logical form of a proposition s is identified with the set of all of its \(i^{\boldsymbol{s}}\)-variants; \(F\) is a logical propositional form therefore iff it is the logical form of at least one proposition. (Please note that according to this approach, the logical form of a purely logical proposition is not even defined; nevertheless, a purely logical proposition can be a member of a logical propositional form.) We will define first the relevant properties for propositional forms: