Deflationism in Logic, Formal Theories of Truth and Philosophy

Abstract

The concept of truth has been studied and used along the areas of philosophy, logic, and mathematics. Although is the same word (“truth”) it has been used in very different ways in each area. Logicians have studied truth in the context of formal theories, while philosophers have examined it in natural languages and the world in general. The Deflationist Theory of Truth, however, seems to be a middle ground between these approaches. According to this theory, truth has a thin nature, meaning that it has little metaphysical content and does not add much to a sentence when used. This work aims to explore how these two approaches can be connected and how deflationism can be understood in them. It specifically addresses the question of conservativity in the formal theory known as the Compositional Theory of Truth and how it relates to deflationism. This project includes a review and critique of the literature on the subject, including its history, logic, results, and the arguments made by its main proponents (such as Tarski, Ramsey, Halbach, Leigh, Field, Horsten, among others). Additionally, this work suggests possible solutions to the questions posed above. The purpose of this thesis was to establish a connection between formal theo- ries of truth, specifically axiomatic theories of truth and the theory of CT , and the philosophical approach to truth, particularly deflationism in formal and natural lan- guage. My main contributions and results are presented in Chapter 5.2 titled "Is truth deflationist?" In this chapter, I propose two distinct labels for different forms of defla- tionism, address the question of whether CT is an appropriate theory for deflationism, with a particular focus on the conservativity feature, and suggest how philosophical and formal approaches can collaborate with each other. This entails considering how the truth predicate behaves in various formal theories when contemplating the nature of truth, as well as taking into account other philosophical positions such as pragmatism or coherence.