ABSTRACT
The main purpose of Professor Quine's article, Two Dogmas of Empiricism, is to discredit a certain group of non-extensional notions, which includes those of logical necessity, logical impossibility, and synonymity or identity of meaning. This chapter shows the characterization is coherent only if we suppose that it makes implicit use of one or more of the notions which it is the main purpose of the article to discredit. Candidates for logical truth not belonging to the propositional logic are equally easily disposed of. The attempt to represent identity of truth-values as a satisfactory extensional substitute for identity of propositions is, then, a failure. But it does not follow from this that no satisfactory extensional substitute can be found. Their truth is quite independent of what the concepts, references, and sub-propositions actually are which they contain; it depends solely on the logical particles together with the relations of identity which exist among these concepts, references, and sub-propositions.
