Thesis--Georgetown University. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 633-649).

Thesis (Ph.D.) - University of St Andrews, September 2009.

Une nouvelle tentative pour faire face au défi sceptique est menée depuis une quarantaine d’années. Cette tentative repose sur une théorie de la connaissance centrée sur la notion d’alternatives pertinentes. La thèse se propose de montrer les faiblesses de cette théorie, même lorsqu’elle s’appuie sur l’appareillage des mondes possibles, et suggère que le scepticisme demeure la meilleure position épistémologique. Dans le premier chapitre on passe en revue une série de difficultés liées au sujet des alternatives pertinentes et l'on essaye d'argumenter en faveur de l'idée qu'il n'y a peut-être pas, finalement, de moyens en quelque sorte objectifs pour établir quelles sont les alternatives pertinentes relativement à une situation quelconque. À partir du deuxième chapitre, il est procédé à une analyse critique des tentatives de certains auteurs qui se sont servis, pour élaborer leurs propres conceptions bien précises, du langage des mondes possibles. Dans le deuxième chapitre, l'on se concentre surtout sur la question du degré de proximité qu'un monde possible donné doit exhiber pour être considéré comme suffisamment proche du monde actuel et l'on essaye de montrer qu'il n’est probablement pas possible de tracer d'une manière non arbitraire une ligne de démarcation entre ces mondes possibles qu’on peut ignorer et ceux qu’on ne peut ignorer dans nos attributions de connaissance. Dans le troisième chapitre, l'on se concentre surtout sur la question des critères qui devraient guider nos évaluations de proximité et l'on essaye de montrer le caractère discutable de n'importe quelle règle visant à établir quels seraient ces critères-là. / Over the last forty years, a new attempt to answer to the skeptic challenge has been proposed. This attempt is based on a theory of knowledge, which is grounded on the notion of relevant alternative. My dissertation aims to show the problems of such a theory, even when formulated in terms of possible worlds, and suggests that in the end skepticism remains the best epistemological option. In the first chapter, I will offer a discussion of the issue of relevant alternatives, and I will argue in favor of the idea that perhaps there are no objective criteria to establish which are the relevant alternatives with respect to a certain given situation. In the second chapter, I will propose a critical analysis of the attempts of some philosophers to formulate their own proposals in the language of possible worlds. In particular, I will focus on the issue of the proximity degree that a certain possible world must have in order to be considered as sufficiently closed to the real world, and I will try to show that perhaps it is not possible to draw a sharp line of demarcation between those possible worlds that we can ignore and those that we must take into account in our attribution of knowledge. In the third chapter, I will critically discuss the criteria that should guide our evaluations about proximity, and I will show the problematic aspects of any rule aimed to establish which these criteria in effect should be.

Over the past few decades analyses of causation have proliferated in almost immeasurable abundance, and with two things in common; firstly, they make much of counterfactual dependence, and secondly, none of them successfully handle all the pre-emption cases. In this thesis, I fore-mostly investigate David Lewis’ promising counterfactual analyses of causation (along with many others), and provide an extensive examination of pre-emption cases. I also offer my own counterfactual analysis of causation, which I argue can handle the problematic pre-emption cases, and therein succeed where so many other prominent analyses of causation have failed. I then conclude with some morals for the continuing debate.

Lewisian Genuine Realism (GR) about possible worlds is often deemed unable to accommodate impossible worlds and reap the benefits that these bestow to rival theories. This thesis explores two alternative extensions of GR into the terrain of impossible worlds. It is divided in six chapters. Chapter I outlines Lewis’ theory, the motivations for impossible worlds, and the central problem that such worlds present for GR: How can GR even understand the notion of an impossible world, given Lewis’ reductive theoretical framework? Since the desideratum is to incorporate impossible worlds into GR without compromising Lewis’ reductive analysis of modality, Chapter II defends that analysis against (old and new) objections. The rest of the thesis is devoted to incorporating impossible worlds into GR. Chapter III explores GR-friendly impossible worlds in the form of set-theoretic constructions out of genuine possibilia. Then, Chapters IV-VI venture into concrete impossible worlds. Chapter IV addresses Lewis’ objection against such worlds, to the effect that contradictions true at impossible worlds amount to true contradictions tout court. I argue that even if so, the relevant contradictions are only ever about the non-actual, and that Lewis’ argument relies on a premise that cannot be nonquestion- beggingly upheld in the face of genuine impossible worlds in any case. Chapter V proposes that Lewis’ reductive analysis can be preserved, even in the face of genuine impossibilia, if we differentiate the impossible from the possible by means of accessibility relations, understood non-modally in terms of similarity. Finally, Chapter VI counters objections to the effect that there are certain impossibilities, formulated in Lewis’ theoretical language, which genuine impossibilia should, but cannot, represent. I conclude that Genuine Realism is still very much in the running when the discussion turns to impossible worlds.