Defeasible conditionals are statements of the form ‘if A then normally B’. One plausible interpretation introduced in nonmonotonic reasoning dictates that ) is true iff B is true in ‘most’ A-worlds. In this paper, we investigate defeasible conditionals constructed upon a notion of ‘overwhelming majority’, defined as ‘truth in a cofinite subset of \’, the first infinite ordinal. One approach employs the modal logic of the frame \\), used in the temporal logic of discrete linear time. We introduce and investigate (...) conditionals, defined modally over \\); several modal definitions of the conditional connective are examined, with an emphasis on the nonmonotonic ones. An alternative interpretation of ‘majority’ as sets cofinal ) rather than cofinite ) is examined. For these modal approaches over \\), a decision procedure readily emerges, as the modal logic \ of this frame is well-known and a translation of the conditional sentences can be mechanically checked for validity; this allows also for a quick proof of \-completeness of the satisfiability problem for these logics. A second approach employs the conditional version of Scott-Montague semantics, in the form of \-many possible worlds, endowed with neighborhoods populated by collections of cofinite subsets of \. This approach gives rise to weak conditional logics, as expected. The relative strength of the conditionals introduced is compared to KLM logics and other conditional logics in the literature. (shrink)

Near the end of 2015, Luis Fariñas del Cerro officially retired as directeur de recherche in the Centre National de Recherche Scientifique (CNRS) and became an Emeritus researcher of the CNRS. The present special issue is a Festschrift in his honour to celebrate Luis’s achievements in science, both as an outstanding scholar as well as a remarkable and highly successful organiser, administrator and leader in science and technology policy and management, in particular as the founder of the Journal of Applied (...) Non-Classical Logics. The issue contains 13 scientific contributions by 32 authors, among them Luis’s colleagues, former students and friends. Preceding versions of these papers were presented at the international workshop ‘Logical Reasoning and Computation’ that was held at IRITInstitut de Recherche en Informatique de Toulouse, Université Paul Sabatier, Toulouse, on 3–4 March 2016. The present introduction contains a short scientific biography describing the many different areas of logic and computation where Luis contributed significant advances. (shrink)

According to the Ramsey Test hypothesis the conditional claim that if A then B is credible just in case it is credible that B, on the supposition that A. If true the hypothesis helps explain the way in which we evaluate and use ordinary language conditionals. But impossibility results for the Ramsey Test hypothesis in its various forms suggest that it is untenable. In this paper, I argue that these results do not in fact have this implication, on the grounds (...) that similar results can be proved without recourse to the Ramsey test hypothesis. Instead they show that a number of well entrenched principles of rational belief and belief revision do not apply to conditionals. (shrink)