Classical Propositional Operators: An Exercise in the Foundations of Logic

This is a book on abstract propositional logic, but it began as a book on modal logic. The first question confronting anyone setting out to write a book on modal logic nowadays is, or ought to be, what sort of thing a modal logic is. An introductory chapter of the projected book was accordiRgly set aside in order to dispose of this question. As I was to realize, it is not as simple as it may appear - at least not if more than a merely stipulative answer is required and one that yields insight. The would-be chapter grew out of proportion, and in the end I decided to publish the eventual jumbo chapter on its own. In preparing the final text I have tried to de-emphasize the modal connection, but it is there, and in Chapter 6 it is explained in detail.