Introduction by the author: The purpose of this book, as its subtitle says, is to introduce readers to late mediaeval logic and semantic theory. By “late mediaeval,” I do not mean the really late period, at the end of the fifteenth century, say. Rather I mean the fourteenth century, primarily, and only the first half of it at that. (That is “late” in comparison with Boethius, certainly, and even in comparison with Peter of Spain and William of Sherwood a century earlier.) This is the period on which I have concentrated the bulk of my research, so naturally it’s the period I’m best in a position to talk about. Nevertheless, to give the reader a running start, I have included a kind of overview in Ch. 2, below, of the history of logic up to the end of the Middle Ages, including the periods before and after the time we will be mainly focusing on. I emphasize that this book is an introduction to the topic. It makes no claim to be — and in any case isn’t — an exhaustive study. I have concentrated on the crucial semantic notions of signification and supposition, and on the interaction of those notions with the theories of mental language and connotation. The result, I think, is a more or less self-contained package of material that is absolutely essential to any further work in late mediaeval logic and semantic theory.