Published online by Cambridge University Press: 12 March 2014
In Part I of this paper no official significance was given to free occurrences of restricted-variables. Indeed doubt has been expressed as to the desirability or feasibility of such usage. Thus, to quote from Rosser [4], p. 146:
“We now raise the question of the significance of F (α), in which the occurrences of α are free [α a variable subject to the restriction K(α)]. In deciding to take (x).K(x) ⊃ F(x) and (Ex).K(x).F(x) as the meanings of (α)F(α) and (Eα)F(α), we were guided by the intuitive meanings. In the case of F(α), the intuitive meaning does not furnish a satisfactory guide. In everyday mathematics, if it has been agreed that α stands for a quantity satisfying the restriction K(α), it is commonly the case that, if one is assuming F (α), then K(α)&F(α) is understood, but if one is trying to prove F (α), then K(α) ⊃ F (α) is understood. It seems that in symbolic logic perhaps it is best not to give any especial significance to α in F(α) when it occurs free.”
Despite this anomalous behaviour we shall, in this Part, show how one can have unhampered use of free restricted-variables in appropriate contexts.