Published online by Cambridge University Press: 12 March 2014
In [1] Ludwik Borkowski takes a quantifier symbol ‘Q1’ (e.g., the familiar ‘∀’) to permit definition of another quantifier symbol ‘Q1’ if, where ‘f’ is a singulary predicate variable, there exists a formula A of QC1—a first-order quantificational calculus (without identity and individual constants) having ‘Q1’ as its one primitive quantifier symbol—such that: (1) under the intended interpretations of ‘Q1’ and ‘Q1’ the biconditional (Q1X)f(X) = A is valid, (2) no individual variable occurs free in A, and (3) A contains no propositional variable, and no predicate variable other than ‘f.’
The research leading to this paper was sponsored by the National Science Foundation, Grant GS-190 (R. Thomason), Grant GS-973 (H. Leblanc), and by the John Simon Guggenheim Memorial Foundation (H. Leblanc). The authors wish to thank Professor A. Mostowski, who drew their attention to the problem discussed here, as well as the referee, who provided many useful comments.