PLEXUS. Philosophical, Logical, and Experimental Routes to Substructurality

Principal Investigator:

Local coordinator: Ricardo Santos

Funding Institution: Horizon Europe Framework Programme (HORIZON) MSCA Staff Exchanges 2021 (HORIZON-MSCA-2021-SE-01)
Date: 2023-2027


The overall goal of PLEXUS is to advance the knowledge of radically substructural logics and deepen our understanding of the broader phenomenon of substructurality, by coordinating the efforts of researchers across the globe, across generations, and across traditions. We see this project as characterised by the following concepts: integration, cross-fertilization and knowledge sharing.

Objective 1. Philosophical Foundations: PLEXUS will investigate the major philosophical challenges raised by non-transitive and non-reflexive substructural logics. In particular, we will investigate the nature of logical theories by addressing the paramount question of whether they are determined inferentially or metainferentially and, if the latter, whether this is done by a single metainferential level or by transfinite hierarchies of metainferences. In doing so, we will also evaluate different accounts of metainferential validity. Moreover, we will revisit legacy tenets such as the identification of sequents with claims of consequence and explore alternative views.

Objective 2. Logic: PLEXUS will advance knowledge of the field of substructural logics by developing new proof-theoretic and model-theoretic characterizations of radically substructural logics. We will develop both proof-theoretic calculi (e.g. hypersequents and labelled calculi) and model-theoretic techniques (including generalisations of the algebraic and model-theoretic characterizations of logics), to analyse the axiomatizations of substructural logics, and explore their meta-logical properties. In addition, we will systematically explore logico-linguistic applications of substructural logics, including theories of self-applicable truth, property instantiation, the logic of grounding, conditionals and models of reasonings under uncertainty.

Objective 3. The Metainferences Inventory & Metainferences Prover: PLEXUS seeks to design and validate a psychometric tool (i.e., the Metainferences Inventory) which would allow us to measure naïve speakers’ preferences on different questions about radical substructurality. We will focus on examining the psychometric properties of the tool (i.e., reliability and validity evidence) through different design phases. Complementary to this research, PLEXUS will extend existing techniques of automated reasoning to the logics covered by the project, focusing particularly on the decision of validity for metainferences.

For more information about PLEXUS contact the local coordinator at email bdicher [at] edu [dot] ulisboa [dot] pt.

Web presence:

Plexus official website:

Plexus blog:

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Research Team

Institutions: University of Navarra (Spain), Faculty of Arts and Humanities of the University of Lisbon, (Portugal), University of Torino (Italy), Ecole Normale Superieure de Paris (France), University of Amsterdam (The Netherlands), The City University of New York (USA), University of Cagliari (Italy), King’s College London (UK), Monash University (Australia), Conjejo Nacional de Investigations Cinetificas y Tecnicas, Argentina