Dynamic Epistemic Logic (DEL) deals with the representation and the study in a multi-agent setting of knowledge and belief change. It can express in a uniform way epistemic statements about: 1. what is true about an initial situation 2. what is true about an event occurring in this situation 3. what is true about the resulting situation after the event has occurred. We axiomatize within the DEL framework what we can infer about (iii) given (i) and (ii). Given three formulas (...) φ,φ' and φ" describing respectively (i), (ii) and (iii), we also show how to build a formula φ ? φ' which captures all the information which can be inferred about (iii) from φ and φ'. We show how our results extend to other modal logics than K. In our proofs and definitions, we resort to a large extent to the normal form formulas for modal logic originally introduced by Kit Fine. In a companion paper (Aucher, 2012), we axiomatize what we can infer about (ii) given (i) and (iii), and what we can infer about (i) given (ii) and (iii), and show how to build two formulas φ ? φ" and φ' ? φ" which capture respectively all the information which can be inferred about (ii) from φ and φ", and all the information which can be inferred about (i) from φ' and φ". (shrink)

Le projet philosophique puise ses sources dans la volonté de proposer une explication rationnelle des phénomènes naturels et culturels qui constituent le monde dans lequel l’être humain prend place. Il a servi de trame culturelle à l’Occident et amené le déploiement d’appareils conceptuels où l’on distingue théorie et pratique. On doit toutefois reconnaître qu’une philosophie théorique peut avoir une portée pratique et l’inverse, puisque toute pratique suppose un ancrage théorique pour légitimer la connaissance et les systèmes normatifs à partir desquels (...) les explications sont avancées. Cela fait dire à certains que la distinction est désormais surannée et qu’une théorie philosophique réunifiée s’impose. Que l’on soit tenant de la tradition ou des nouvelles approches, la philosophie pratique s’impose désormais comme un passage obligé pour réfléchir les problèmes et articuler de nouvelles théories faisant écho à l’état actuel de notre monde. Le présent ouvrage revient sur la notion de philosophie pratique afin d’en faire voir les différentes acceptions et manières de la mobiliser pour réfléchir à des problèmes actuels. (shrink)

Dynamic epistemic logics provide an account of the evolution of agents’ belief and knowledge when they learn the occurrence of an event. These logics started to become popular about 20 years ago and by now there exists a huge number of publications about them. The present paper briefly summarises the existing body of literature, discusses some problems and shortcomings, and proposes some avenues for future research.

This chapter presents a new semantics for inductive empirical knowledge. The epistemic agent is represented concretely as a learner who processes new inputs through time and who forms new beliefs from those inputs by means of a concrete, computable learning program. The agent’s belief state is represented hyper-intensionally as a set of time-indexed sentences. Knowledge is interpreted as avoidance of error in the limit and as having converged to true belief from the present time onward. Familiar topics are re-examined within (...) the semantics, such as inductive skepticism, the logic of discovery, Duhem’s problem, the articulation of theories by auxiliary hypotheses, the role of serendipity in scientific knowledge, Fitch’s paradox, deductive closure of knowability, whether one can know inductively that one knows inductively, whether one can know inductively that one does not know inductively, and whether expert instruction can spread common inductive knowledge—as opposed to mere, true belief—through a community of gullible pupils. (shrink)