The Liar Speaks the Truth

Abstract In this book Yaqub describes a simple conception of truth and shows that it yields a semantical theory that accommodates the whole range of our seemingly conflicting intuitions about truth. This conception takes the Tarskian biconditionals (such as “The sentence `Johannes loved Clara’ is true if and only if Johannes loved Clara”) as correctly and completely defining the notion of truth. The semantical theory, which is called the revision theory, that emerges from this conception paints a metaphysical picture of truth as a property whose applicability is given by a revision process rather than by a fixed extension. The main advantage of this revision process is its ability to explain why truth seems in many cases almost redundant, in others substantial, and yet in others paradoxical (as in the famous Liar). Yaqub offers a comprehensive defense of the revision theory of truth by developing consistent and adequate formal semantics for languages in which all sorts of problematic sentences (Liar and company) can be constructed. He also offers a detailed critical exposition of the proposals of Herzberger, Gupta, and Belnap. Yaqub concludes by introducing a logic of truth that further demonstrates the adequacy of the revision theory. The book starts with a basic and intuitive understanding of the notion of truth and ends with a complex logic of truth. This book will interest students of logic, truth theory, formal semantics, and philosophy of language.