Suszko's Problem: Mixed Consequence and Compositionality

Suszko's problem is the problem of finding the minimal number of truth values needed to semantically characterize a syntactic consequence relation. Suszko proved that every Tarskian consequence relation can be characterized using only two truth values. Malinowski showed that this number can equal three if some of Tarski's structural constraints are relaxed. By so doing, Malinowski introduced a case of so-called mixed consequence, allowing the notion of a designated value to vary between the premises and the conclusions of an argument. In this paper we give a more systematic perspective on Suszko's problem and on mixed consequence. First, we prove general representation theorems relating structural properties of a consequence relation to their semantic interpretation, uncovering the semantic counterpart of substitution-invariance, and establishing that (intersective) mixed consequence is fundamentally the semantic counterpart of the structural property of monotonicity. We use those to derive maximum-rank results proved recently in a different setting by French and Ripley, as well as by Blasio, Marcos and Wansing, for logics with various structural properties (reflexivity, transitivity, none, or both). We strengthen these results into exact rank results for non-permeable logics (roughly, those which distinguish the role of premises and conclusions). We discuss the underlying notion of rank, and the associated reduction proposed independently by Scott and Suszko. As emphasized by Suszko, that reduction fails to preserve compositionality in general, meaning that the resulting semantics is no longer truth-functional. We propose a modification of that notion of reduction, allowing us to prove that over compact logics with what we call regular connectives, rank results are maintained even if we request the preservation of truth-functionality and additional semantic properties.Comment: Keywords: Suszko's thesis; truth value; logical consequence; mixed consequence; compositionality; truth-functionality; many-valued logic; algebraic logic; substructural logics; regular connective

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Philosophy and Phenomenological Research, EarlyView

The Substructural Solution to Paradoxes and the Problem of the Dependence

En los últimos años se han desarrollado diversas soluciones subestructurales a las paradojas semánticas. En particular, se han postulado teorías no transitivas, no contractivas, no reflexivas y, recientemente, no monotónicas. Sin embargo, cuando dichas soluciones son presentadas mediante cálculos de secuentes surge el problema de la dependencia . En pocas palabras, este problema consiste en que no es posible separar las reglas estructurales de la formulación de las otras reglas del cálculo. En este artículo, presentaré este problema y mostraré que, de hecho, es posible construir un cálculo que no contiene ninguna regla estructural de manera explícita y que, sin embargo, resulta trivial al agregarle un predicado veritativo transparente con ciertos axiomas. Luego, delimitaré los alcances de dicho problema, concluyendo que la metodología correcta para seleccionar una solución subestructural a las paradojas semánticas debe basarse en argumentos filosóficos y, tal vez, en un estudio empírico sobre el fenómeno de la paradojicidad y no en la comparación de derivaciones en cálculos particulares.In past years, several substructural solutions to semantical paradoxes have been developed. In particular, nontransitive, noncontractive, nonmonotonic and nonreflexive theories have been proposed. However, when such solutions are presented using sequent-calculi it emerges what I call the problem of the dependence. In a nutshell, this problem consists in that it’s not easy (or sometimes even possible) to distinguish between the structural rules and the other rules of the calculus. In this article, I will present in detail this problem and I show that even worst there is a calculus such that it doesn’t contain any structural rule but cannot nontrivially handle semantical vocabulary. Finally, I will delimit this problem and I will conclude that the correct methodology for preferring one specific substructural theory should be based on philosophical arguments (or in some case, on empirical bases), but not in the comparison between derivations in particular calculi.Fil: Da Re, Bruno. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Filosóficas. - Sociedad Argentina de Análisis Filosófico. Instituto de Investigaciones Filosóficas; Argentin

Three Essays on Substructural Approaches to Semantic Paradoxes

This thesis consists of three papers on substructural approaches to semantic paradoxes. The first paper introduces a formal system, based on a nontransitive substructural logic, which has exactly the valid and antivalid inferences of classical logic at every level of (meta)inference, but which I argue is still not classical logic. In the second essay, I introduce infinite-premise versions of several semantic paradoxes, and show that noncontractive substructural approaches do not solve these paradoxes. In the third essay, I introduce an infinite metainferential hierarchy of validity curry paradoxes, and argue that providing a uniform solution to the paradoxes in this hierarchy makes substructural approaches less appealing. Together, the three essays in this thesis illustrate a problem for substructural approaches: substructural logics simply do not do everything that we need a logic to do, and so cannot solve semantic paradoxes in every context in which they appear. A new strategy, with a broader conception of what constitutes a uniform solution, is needed