ABSTRACT
Values of variables, as opposed to values of propositional functions, can be all sorts of things. As late as 1959, Bertrand Russell distinguishes between “values of the function” and “values of the variable” in a similar way. The content of the proposition is preserved to varying degrees, but never altered. Different terms are always replaced with different variables, but different occurrences of the same term may be and usually are replaced with occurrences of the same variable. The content of the proposition is preserved to varying degrees, but never altered. Propositions are beliefs that sentences express. In his 1919 Introduction to Mathematical Philosophy, Russell says that “there was never any clear account of what is added to truth by the conception of necessity”. Raymond Bradley has cited only a few of the papers and books in which Russell discusses modality.
