RT Book, Section T1 On the philosophy and mathematics of hybrid partial type theory A1 Aranda Utrero, Víctor A1 Huertas, Antonia A1 Manzano, María A1 Martins, Manuel A2 Antunes, Henrique A2 Freire, Alfredo Roque A2 Rodrigues, Abilio AB The aim of this paper is to present the philosophical influences and motivations of Hybrid Partial Type Theory (HPTT), a partial type theory combined with a strong version of hybrid logic in which the concepts of existence and denotation emerge naturally. The text is divided into three main parts. Firstly, we present and discuss some formal systems dealing with existence and denotation in both first-order logic and type theory. Then, we move to the framework of modal logic, introducing the distinction between constant and varying domains, as well as the hybrid machinery. Finally, we give a succinct account of the semantics of HPTT and provide new definitions of existence and denotation within the system, together with a reflection on de dicto and de re statements and some validities sharing an explicit philosophical characterization. PB Springer SN 978-3-032-11026-8 SN 978-3-032-11029-9 SN 978-3-032-11027-5 YR 2026 FD 2026 LK https://hdl.handle.net/20.500.14352/137077 UL https://hdl.handle.net/20.500.14352/137077 LA eng NO Aranda, V., Huertas, A., Manzano, M., Martins, M. (2026). On the Philosophy and Mathematics of Hybrid Partial Type Theory. In: Antunes, H., Freire, A.R., Rodrigues, A. (eds) Walter Carnielli on Reasoning, Paraconsistency, and Probability. Outstanding Contributions to Logic, vol 32. Springer, Cham. https://doi.org/10.1007/978-3-032-11027-5_3 NO First Online: 10 November 2025. NO Comunidad de Madrid NO Universidad Complutense de Madrid DS Docta Complutense RD 7 jun 2026