Predicate calculus with free quantifier variables
Richmond H. Thomason, Denise R. Johnson · Journal of Symbolic Logic · 1969
In the literature of symbolic logic there are many examples of systems having free variables ranging over truth-values, individuals, or predicates. But, though many such systems are equipped with universal and existential quantifiers (and though many other quantifiers, e.g., for exactly one, are thereby definable), the problem of free variables corresponding to such constants has been neglected.