Published online by Cambridge University Press: 12 March 2014
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.
The research resulting in this paper was sponsored by the National Science Foundation, under grant GS-1567. The authors wish to thank the referee for his helpful suggestions.