José Martínez

Here, I first prove that certain families of k-valued clones have the Gupta-Belnap fixed-point property. This essentially means that all propositional languages that are interpreted with operators belonging to those clones are such that any net of self-referential sentences in the language can be consistently evaluated. I then focus on two four-valued generalisations of the Kleene propositional operators that generalise the strong and weak Kleene operators: Belnap’s clone and Fitting’s clone, respectively. I apply the theorems from the initial part of the paper to analyse the fixed-point property of Belnap’s and Fitting’s clones when some special operators that reflect the semantics are added. The conclusion of the paper is that Fitting’s clone is better suited than Belnap’s to provide self-referential languages with highly expressive resources.

This anthology of the very latest research on truth features the work of recognized luminaries in the field, put together following a rigorous refereeing process. Along with an introduction outlining the central issues in the field, it provides a unique and unrivaled view of contemporary work on the nature of truth, with papers selected from key conferences in 2011 such as Truth Be Told, Truth at Work, Paradoxes of Truth and Denotation and Axiomatic Theories of Truth. Studying the nature of the concept of ‘truth’ has always been a core role of philosophy, but recent years have been a boom time in the topic. With a wealth of recent conferences examining the subject from various angles, this collection of essays recognizes the pressing need for a volume that brings scholars up to date on the arguments. Offering academics and graduate students alike a much-needed repository of today’s cutting-edge work in this vital topic of philosophy, the volume is required reading for anyone needing to keep abreast of developments, and is certain to act as a catalyst for further innovation and research.

Ŷābir b. Aflaḥ al-Išbīlī, conocido como Geber filius Afflay Hispalensis en la Europa medieval, fue un matemático y astrónomo teórico que probablemente floreció en Sevilla durante el primer cuarto del s. XII. Ŷābir b. Aflaḥ es un astrónomo medieval importante gracias a su obra principal, IIṣlāḥ al-Maŷisṭī, traducida al latín y al hebreo. Con el IIṣlāḥ al-Maŷisṭī, su autor pretende reescribir el Almagesto a la vez que introduce algunas correcciones. En 1984, A.I. Sabra, en su importante artículo «The Andalusian revolt against Ptolemaic astronomy» llama la atención sobre un grupo de filósofo andalusíes, contemporáneos de Ŷābir b. Aflaḥ o que florecieron poco después que él —como Ibn Baŷŷa (m. 537/1138), Ibn Ṭufayl (m. 581/1185), Ibn Rušd (m. 595/1198), Maimónides (m. 601/1204) y al-Biṭrūŷī (fl. 596/1200)—, quienes criticaron, desde un punto de vista cosmológico, los modelos astronómicos descritos en el Almagesto al no ser coherentes con la física aristotélica. La finalidad de este artículo es describir el tipo de críticas que hace Ŷābir b. Aflaḥ a Ptolomeo con el objeto de dilucidar si cabe considerarlo uno de los miembros de la rebelión andalusí contra la astronomía ptolemaica. La conclusión final es que las críticas de Ŷābir b. Aflaḥ no son de carácter cosmológico —si bien puedan tener consecuencias cosmológicas—, sino que son de carácter matemático y técnico. Así pues, no cabe considerarlo un miembro de la rebelión andalusí contra la astronomía ptolemaica.