On some recently debated issues in the theory of formal truth

As the title suggests, this paper aims at surveying some recent advances in the theory of formal truth. It contains an account of the debate concerning the deflationist approach to truth, according to which truth is a ‘thin’ notion in that it should involve no assumption of whatsoever nature. We review here the main issues that were comprised by the discussion accompanying the attempts of translating this idea into logical terms. In the second half of the paper, we focus on a recent theory of truth proposed by Hartry Field, a former ‘champion’ of the deflationary approach. We then discuss it both with respect to the previous conceptual account, and to some further observation concerning the truth–as–revision machinery that this theory can be proved to implicitly make use of

Semantic Paradoxes and Transparent Intensional Logic

The paper describes the solution to semantic paradoxes pioneered by Pavel Tichý and further developed by the present author. Its main feature is an examination (and then refutation) of the hidden premise of paradoxes that the paradox-producing expression really means what it seems to mean. Semantic concepts are explicated as relative to language, thus also language is explicated. The so-called ‘explicit approach’ easily treats paradoxes in which language is explicitly referred to. The residual paradoxes are solved by the ‘implicit approach’ which employs ideas made explicit by the former one

Procedural Semantics and its Relevance to Paradox

Two semantic paradoxes, the Liar and Curry’s paradox, are analysed using a newly developed conception of procedural semantics (semantics according to which the truth of propositions is determined algorithmically), whose main characteristic is its departure from methodological realism. Rather than determining pre-existing facts, procedures are constitutive of them. Of this semantics, two versions are considered: closed (where the halting of procedures is presumed) and open (without this presumption). To this end, a procedural approach to deductive reasoning is developed, based on the idea of simulation. As is shown, closed semantics supports classical logic, but cannot in any straightforward way accommodate the concept of truth. In open semantics, where paradoxical propositions naturally ‘belong’, they cease to be paradoxical; yet, it is concluded that the natural choice—for logicians and common people alike—is to stick to closed semantics, pragmatically circumventing problematic utterances

Type-free truth

This book is a contribution to the flourishing field of formal and philosophical work on truth and the semantic paradoxes. Our aim is to present several theories of truth, to investigate some of their model-theoretic, recursion-theoretic and proof-theoretic aspects, and to evaluate their philosophical significance. In Part I we first outline some motivations for studying formal theories of truth, fix some terminology, provide some background on Tarski’s and Kripke’s theories of truth, and then discuss the prospects of classical type-free truth. In Chapter 4 we discuss some minimal adequacy conditions on a satisfactory theory of truth based on the function that the truth predicate is intended to fulfil on the deflationist account. We cast doubt on the adequacy of some non-classical theories of truth and argue in favor of classical theories of truth. Part II is devoted to grounded truth. In chapter 5 we introduce a game-theoretic semantics for Kripke’s theory of truth. Strategies in these games can be interpreted as reference-graphs (or dependency-graphs) of the sentences in question. Using that framework, we give a graph-theoretic analysis of the Kripke-paradoxical sentences. In chapter 6 we provide simultaneous axiomatizations of groundedness and truth, and analyze the proof-theoretic strength of the resulting theories. These range from conservative extensions of Peano arithmetic to theories that have the full strength of the impredicative system ID1. Part III investigates the relationship between truth and set-theoretic comprehen- sion. In chapter 7 we canonically associate extensions of the truth predicate with Henkin-models of second-order arithmetic. This relationship will be employed to determine the recursion-theoretic complexity of several theories of grounded truth and to show the consistency of the latter with principles of generalized induction. In chapter 8 it is shown that the sets definable over the standard model of the Tarskian hierarchy are exactly the hyperarithmetical sets. Finally, we try to apply a certain solution to the set-theoretic paradoxes to the case of truth, namely Quine’s idea of stratification. This will yield classical disquotational theories that interpret full second-order arithmetic without set parameters, Z2- (chapter 9). We also indicate a method to recover the parameters. An appendix provides some background on ordinal notations, recursion theory and graph theory

Replies to Bacon, Eklund, and Greenough on Replacing Truth

Andrew Bacon, Matti Eklund, and Patrick Greenough have individually proposed objections to the project in my book, Replacing Truth. Briefly, the book outlines a conceptual engineering project – our defective concept of truth is replaced for certain purposes with a team of concepts that can do some of the jobs we thought truth could do. Here, I respond to their objections and develop the views expressed in Replacing Truth in various ways.PostprintNon peer reviewe

The Notion of Truth through Dialetheism, Deflationism and Fictionalism

In the present work three different areas about the truth predicate coexist: the semantic area, whose focus is on theories dealing with the solution to the semantic paradoxes that involve the truth predicate; the ontological area, which covers the theories investigating the nature of truth; and the area of discourse, in which the focus is on those theories that analyse how the discourse about the truth predicate has to be understood. The aim of this work is to analyze the consequences arising from certain specific ways in which these areas can interact with each other. The first three chapters expose the main features of the theories corresponding to the three areas about the truth predicate, respectively dialetheism, deflationism and fictionalism. The possible combinations between those theories are the focus of the two following chapters. Finally, a new attempt to account for the liar paradox is provided