We develop a Bayesian framework for thinking about the way evidence about the here and now can bear on hypotheses about the qualitative character of the world as a whole, including hypotheses according to which the total population of the world is infinite. We show how this framework makes sense of the practice cosmologists have recently adopted in their reasoning about such hypotheses.

The best-known argument for Evidential Decision Theory (EDT) is the ‘Why ain’cha rich?’ challenge to rival Causal Decision Theory (CDT). The basis for this challenge is that in Newcomb-like situations, acts that conform to EDT may be known in advance to have the better return than acts that conform to CDT. Frank Arntzenius has recently proposed an ingenious counter argument, based on an example in which, he claims, it is predictable in advance that acts that conform to EDT will (...) do less well than acts that conform to CDT. We raise two objections to Arntzenius’s example. We argue, first, that the example is subtly incoherent, in a way that undermines its effectiveness against EDT; and, second, that the example relies on calculating the average return over an inappropriate population of acts. (shrink)

Theories that use expected utility maximization to evaluate acts have difficulty handling cases with infinitely many utility contributions. In this paper I present and motivate a way of modifying such theories to deal with these cases, employing what I call “Direct Difference Taking”. This proposal has a number of desirable features: it’s natural and well-motivated, it satisfies natural dominance intuitions, and it yields plausible prescriptions in a wide range of cases. I then compare my account to the most plausible alternative, (...) a proposal offered by Arntzenius :31–58, 2014). I argue that while Arntzenius’s proposal has many attractive features, it runs into a number of problems which Direct Difference Taking avoids. (shrink)

For aggregative theories of moral value, it is a challenge to rank worlds that each contain infinitely many valuable events. And, although there are several existing proposals for doing so, few provide a cardinal measure of each world's value. This raises the even greater challenge of ranking lotteries over such worlds—without a cardinal value for each world, we cannot apply expected value theory. How then can we compare such lotteries? To date, we have just one method for doing so (proposed (...) separately by Arntzenius, Bostrom, and Meacham), which is to compare the prospects for value at each individual location, and to then represent and compare lotteries by their expected values at each of those locations. But, as I show here, this approach violates several key principles of decision theory and generates some implausible verdicts. I propose an alternative—one which delivers plausible rankings of lotteries, which is implied by a plausible collection of axioms, and which can be applied alongside almost any ranking of infinite worlds. (shrink)

I argue that what evidence an agent has does not supervene on how she currently is. Agents do not always have to infer what the past was like from how things currently seem; sometimes the facts about the past are retained pieces of evidence that can be the start of reasoning. The main argument is a variant on Frank Arntzenius’s Shangri La example, an example that is often used to motivate the thought that evidence does supervene on current features.

Could space consist entirely of extended regions, without any regions shaped like points, lines, or surfaces? Peter Forrest and Frank Arntzenius have independently raised a paradox of size for space like this, drawing on a construction of Cantor’s. I present a new version of this argument and explore possible lines of response.

In this paper, I argue that the recent discussion on the time - reversal invariance of classical electrodynamics (see (Albert 2000: ch.1), (Arntzenius 2004), (Earman 2002), (Malament 2004),(Horwich 1987: ch.3)) can be best understood assuming that the disagreement among the various authors is actually a disagreement about the metaphysics of classical electrodynamics. If so, the controversy will not be resolved until we have established which alternative is the most natural. It turns out that we have a paradox, namely that (...) the following three claims are incompatible: the electromagnetic fields are real, classical electrodynamics is time-reversal invariant, and the content of the state of affairs of the world does not depend on whether it belongs to a forward or a backward sequence of states of the world. (shrink)

In “Bayesianism, Infinite Decisions, and Binding”, Arntzenius et al. (Mind 113:251–283, 2004 ) present cases in which agents who cannot bind themselves are driven by standard decision theory to choose sequences of actions with disastrous consequences. They defend standard decision theory by arguing that if a decision rule leads agents to disaster only when they cannot bind themselves, this should not be taken to be a mark against the decision rule. I show that this claim has surprising implications for (...) a number of other debates in decision theory. I then assess the plausibility of this claim, and suggest that it should be rejected. (shrink)

The impetus theory of motion states that to be in motion is to have a non-zero velocity. The at-at theory of motion states that to be in motion is to be at different places at different times, which in classical physics is naturally understood as the reduction of velocities to position developments. I first defend the at-at theory against the criticism raised by Arntzenius that it renders determinism impossible. I then develop a novel impetus theory of motion that reduces (...) positions to velocity developments. As this impetus theory of motion is by construction a mirror image of the at-at theory of motion, I claim that the two theories of motion are in fact epistemically on par—despite the unfamiliar metaphysical picture of the world furnished by the impetus version. (shrink)

În această lucrare analizez posibilitatea călătoriei în timp pe baza mai multor lucrări de specialitate, printre care cele ale lui Nicholas J.J. Smith ("Time Travel", The Stanford Encyclopedia of Philosophy”), William Grey (”Troubles with Time Travel”), Ulrich Meyer (”Explaining causal loops”), Simon Keller și Michael Nelson (”Presentists should believe in time-travel”), Frank Arntzenius și Tim Maudlin ("Time Travel and Modern Physics") și David Lewis (“The Paradoxes of Time Travel”). Lucrarea începe cu o Introducere în care fac o scurtă prezentare (...) a călătoriei în timp, și continuă cu o Istoria conceptului de călătorie în timp, prezentarea principalelor Aspecte fizice ale călătoriei în timp, inclusiv călătoria în timp în trecut în relativitatea generală și în fizica cuantică și călătoria în timp în viitor, apoi o prezentare a Paradoxul bunicului care este abordat în aproape toate lucrările de specialitate, urmat de o secțiune dedicată Filosofiei călătoriei în timp, și o secțiune în care analizez Buclele cauzale pentru călătoria în timp. Finalizez lucrarea cu Concluzii, în care expun opiniile personale privind călătoria în timp, și Bibliografia pe care se bazează lucrarea. (shrink)

Andy Egan recently drew attention to a class of decision situations that provide a certain kind of informational feedback, which he claims constitute a counterexample to causal decision theory. Arntzenius and Wallace have sought to vindicate a form of CDT by describing a dynamic process of deliberation that culminates in a “mixed” decision. I show that, for many of the cases in question, this proposal depends on an incorrect way of calculating expected utilities, and argue that it is therefore (...) unsuccessful. I then tentatively defend an alternative proposal by Joyce, which produces a similar process of dynamic deliberation but for a different reason. (shrink)

In this article, I argue that it is impossible to complete infinitely many tasks in a finite time. A key premise in my argument is that the only way to get to 0 tasks remaining is from 1 task remaining, when tasks are done 1-by-1. I suggest that the only way to deny this premise is by begging the question, that is, by assuming that supertasks are possible. I go on to present one reason why this conclusion (that supertasks are (...) impossible) is important, namely that it implies a new verdict on a decision puzzle propounded by Jeffrey Barrett and Frank Arntzenius. (shrink)

The problem of the man who met death in Damascus appeared in the infancy of the theory of rational choice known as causal decision theory. A straightforward, unadorned version of causal decision theory is presented here and applied, along with Brian Skyrms’ deliberation dynamics, to Death in Damascus and similar problems. Decision instability is a fascinating topic, but not a source of difficulty for causal decision theory. Andy Egan’s purported counterexample to causal decision theory, Murder Lesion, is considered; a simple (...) response shows how Murder Lesion and similar examples fail to be counterexamples, and clarifies the use of the unadorned theory in problems of decision instability. I compare unadorned causal decision theory to previous treatments by Frank Arntzenius and by Jim Joyce, and recommend a well-founded heuristic that all three accounts can endorse. Whatever course deliberation takes, causal decision theory is consistently a good guide to rational action. (shrink)

À propos de la possibilité de voyager dans le temps sur la base de plusieurs ouvrages spécialisés, notamment ceux de Nicholas J. J. Smith (« Time Travel »), William Grey (« Troubles with Time Travel »), Ulrich Meyer (« Explaining causal loops »), Simon Keller and Michael Nelson (« Presentists should believe in time-travel »), Frank Arntzenius and Tim Maudlin (« Time Travel and Modern Physics »), et David Lewis (« The Paradoxes of Time Travel »). L'article commence par (...) une Introduction dans laquelle je fais une brève présentation du voyage dans le temps et poursuit par une Histoire du concept de voyage dans le temps, les principaux aspects physiques du voyage dans le temps, y compris les voyages dans le temps dans le passé dans la relativité générale et la physique quantique , et les voyages dans le temps dans le futur, puis une présentation du Paradoxe du grand-père abordé dans presque toutes les œuvres spécialisées, suivie d’une section consacrée à la Philosophie du voyage dans le temps et d’une section dans laquelle j’analyse les Boucles causales pour le voyage dans le temps. Je termine mon travail avec Conclusions, dans laquelle je maintiens mes opinions personnelles sur le voyage dans le temps et la Bibliographie sur laquelle repose le travail. -/- TABLE: -/- Abstract Introducere Istoria conceptului de călătorie în timp Paradoxul bunicului Filosofía călătoriei în timp Buclele cauzale Concluzii Note Bibliografie -/- DOI: 10.13140/RG.2.2.27116.51841. (shrink)

Une autre définition du voyage dans le temps (Arntzenius 2006) (Smeenk and Wüthrich 2011) l'assimile à l'existence des courbes temporelles fermées, une variété lorentzienne d'une particule matérielle dans l'espace-temps qui revient à son point de départ. Certains auteurs acceptent l’existence de deux dimensions temporelles et d’autres envisagent des scénarios comportant plusieurs univers « parallèles », chacun ayant son propre espace-temps à quatre dimensions.Mais la question est de savoir si un voyage dans une autre dimension temporelle ou dans un autre (...) univers parallèle est en fait un voyage dans le temps ou virtuel. Examiner la possibilité de revenir dans le temps dans un univers hypothétique décrit par une métrique de Gödel a amené Kurt Gödel à affirmer que le temps pouvait être une sorte d’illusion, une autre dimension de l’espace, donnant lieu à un « bloc à 4 dimensions. ». (shrink)

About the possibility of time traveling based on several specialized works, including those of Nicholas J. J. Smith ("Time Travel"), William Grey (”Troubles with Time Travel”), Ulrich Meyer (”Explaining causal loops”), Simon Keller and Michael Nelson (”Presentists should believe in time-travel”), Frank Arntzenius and Tim Maudlin ("Time Travel and Modern Physics"), and David Lewis (“The Paradoxes of Time Travel”). The article begins with an Introduction in which I make a short presentation of the time travel, and continues with a (...) History of the concept of time travel, main physical aspects of time travel, including backward time travel in the past in general relativity and quantum physics, and time travel in the future, then a presentation of the Grandfather paradox that is approached in almost all specialized works, followed by a section dedicated to the Philosophy of time travel, and a section in which I analyze Causal loops for time travel. I finish my work with Conclusions, in which I sustain my personal opinions on the time travel, and the Bibliography on which the work is based. -/- ISSN 978-606-033-195-7, DOI: 10.58679/TW82554. (shrink)