ABSTRACT
In order to express the forms of propositions of this second sort, reader need some symbols not found in Lower Predicate Calculus-1, viz. individual-variables, for which they use the sequence of small letters beginning ‘x’, ‘y’, … These variables take as their values names of individuals; more accurately, their values are the names or other designations of the individuals (objects, people, numbers – whatever they may be) in the relevant universe of discourse. Every Well-formed formula of Lower Predicate Calculus-2 becomes a proposition in some universe of discourse if for every individual-variable in it there is uniformly substituted a name or other designation of some object in that universe of discourse, and for every predicate variable in it there is uniformly substituted an expression designating some property which objects in that universe of discourse can be said to possess or to lack.
