In order to predict and explain behavior, one cannot specify the mental state of an agent merely by saying what information she possesses. Instead one must specify what information is available to an agent relative to various purposes. Specifying mental states in this way allows us to accommodate cases of imperfect recall, cognitive accomplishments involved in logical deduction, the mental states of confused or fragmented subjects, and the difference between propositional knowledge and know-how .

When one encounters disagreement about the truth of a factual claim from a trusted advisor who has access to all of one's evidence, should that move one in the direction of the advisor's view? Conciliatory views on disagreement say "yes, at least a little." Such views are extremely natural, but they can give incoherent advice when the issue under dispute is disagreement itself. So conciliatory views stand refuted. But despite first appearances, this makes no trouble for *partly* conciliatory views: views (...) that recommend giving ground in the face of disagreement about many matters, but not about disagreement itself. (shrink)

The 'best-system' analysis of lawhood [Lewis 1994] faces the 'zero-fit problem': that many systems of laws say that the chance of history going actually as it goes--the degree to which the theory 'fits' the actual course of history--is zero. Neither an appeal to infinitesimal probabilities nor a patch using standard measure theory avoids the difficulty. But there is a way to avoid it: replace the notion of 'fit' with the notion of a world being typical with respect to a theory.

There are 1,000 of us and one victim. We each increase the level at which a "discomfort machine" operates on the victim---leading to great discomfort. Suppose that consecutive levels of the machine are so similar that the victim cannot distinguish them. Have we acted permissibly? According to the "no-difference argument" the answer is "yes" because each of our actions was guaranteed to make the victim no worse off. This argument is of interest because if it is sound, similar arguments threaten (...) intuitive moral verdicts about many cases in which a large number of individual choices cumulatively make a great difference, while each choice seems to make no difference on its own. But the argument is not sound, as is shown by a simple objection based on a plausible dominance principle---an objection that avoids challenges that have been brought against previous criticisms of the no difference argument. (shrink)

How should you take into account the opinions of an advisor? When you completely defer to the advisor's judgment, then you should treat the advisor as a guru. Roughly, that means you should believe what you expect she would believe, if supplied with your extra evidence. When the advisor is your own future self, the resulting principle amounts to a version of the Reflection Principle---a version amended to handle cases of information loss. When you count an advisor as an epistemic (...) peer, you should give her conclusions the same weight as your own. Denying that view---call it the ``equal weight view''---leads to absurdity: the absurdity that you could reasonably come to believe yourself to be an epistemic superior to an advisor simply by noting cases of disagreement with her, and taking it that she made most of the mistakes. Accepting the view seems to lead to another absurdity: that one should suspend judgment about everything that one's smart and well-informed friends disagree on, which means suspending judgment about almost everything interesting. But despite appearances, the equal weight view does not have this absurd consequence. Furthermore, the view can be generalized to handle cases involving not just epistemic peers, but also epistemic superiors and inferiors. (shrink)

In addition to being uncertain about what the world is like, one can also be uncertain about one’s own spatial or temporal location in the world. My aim is to pose a problem arising from the interaction between these two sorts of uncertainty, solve the problem, and draw two lessons from the solution.

It would be good to have a Bayesian decision theory that assesses our decisions and thinking according to everyday standards of rationality — standards that do not require logical omniscience (Garber 1983, Hacking 1967). To that end we develop a “fragmented” decision theory in which a single state of mind is represented by a family of credence functions, each associated with a distinct choice condition (Lewis 1982, Stalnaker 1984). The theory imposes a local coherence assumption guaranteeing that as an agent's (...) attention shifts, successive batches of "obvious" logical information become available to her. A rule of expected utility maximization can then be applied to the decision of what to attend to next during a train of thought. On the resulting theory, rationality requires ordinary agents to be logically competent and to often engage in trains of thought that increase the unification of their states of mind. But rationality does not require ordinary agents to be logically omniscient. (shrink)

Many have claimed that unspecific evidence sometimes demands unsharp, indeterminate, imprecise, vague, or interval-valued probabilities. Against this, a variant of the diachronic Dutch Book argument shows that perfectly rational agents always have perfectly sharp probabilities.

The “puzzle of the unmarked clock” derives from a conflict between the following: (1) a plausible principle of epistemic modesty, and (2) “Rational Reflection”, a principle saying how one’s beliefs about what it is rational to believe constrain the rest of one’s beliefs. An independently motivated improvement to Rational Reflection preserves its spirit while resolving the conflict.

In "Counterfactual Dependence and Time's Arrow", David Lewis defends an analysis of counterfactuals intended to yield the asymmetry of counterfactual dependence: that later affairs depend counterfactually on earlier ones, and not the other way around. I argue that careful attention to the dynamical properties of thermodynamically irreversible processes shows that in many ordinary cases, Lewis's analysis fails to yield this asymmetry. Furthermore, the analysis fails in an instructive way: it teaches us something about the connection between the asymmetry of overdetermination (...) and the asymmetry of entropy. (shrink)

Dr. Evil learns that a duplicate of Dr. Evil has been created. Upon learning this, how seriously should he take the hypothesis that he himself is that duplicate? I answer: very seriously. I defend a principle of indifference for self-locating belief which entails that after Dr. Evil learns that a duplicate has been created, he ought to have exactly the same degree of belief that he is Dr. Evil as that he is the duplicate. More generally, the principle shows that (...) there is a sharp distinction between ordinary skeptical hypotheses, and self-locating skeptical hypotheses. (shrink)

(1) Suppose that you care only about speaking the truth, and are confident that some particular deterministic theory is true. If someone asks you whether that theory is true, are you rationally required to answer "yes"? -/- (2) Suppose that you face a problem in which (as in Newcomb's problem) one of your options---call it "taking two boxes"---causally dominates your only other option. Are you rationally required to take two boxes? -/- Those of us attracted to causal decision theory are (...) under pressure to answer "yes" to both questions. However, it has been shown that many existing decision theories are inconsistent with doing so (Ahmed 2014). A simple proof shows that the same goes for an even wider class of theories: all "suppositional" decision theories. The moral is that causal decision theorists must either answer "no" to one of the above questions, or else abandon suppositional decision theories. (shrink)

 Fred comes to realize that if his parents had settled in a more conservative neighborhood, he would have—on the basis of essentially the same evidence—arrived at political views quite different from his actual views. Furthermore, his parents chose between liberal and conservative neighborhoods by tossing a coin. (Sher 2001).

We pose and resolve several vexing decision theoretic puzzles. Some are variants of existing puzzles, such as 'Trumped' (Arntzenius and McCarthy 1997), 'Rouble trouble' (Arntzenius and Barrett 1999), 'The airtight Dutch book' (McGee 1999), and 'The two envelopes puzzle' (Broome 1995). Others are new. A unified resolution of the puzzles shows that Dutch book arguments have no force in infinite cases. It thereby provides evidence that reasonable utility functions may be unbounded and that reasonable credence functions need not be countably (...) additive. The resolution also shows that when infinitely many decisions are involved, the difference between making the decisions simultaneously and making them sequentially can be the difference between riches and ruin. Finally, the resolution reveals a new way in which the ability to make binding commitments can save perfectly rational agents from sure losses. (shrink)

I was more excited by Jacques Ranciere’s idea about aesthetics being, in his opinion, a special way of thinking (mode de pensee) that works of art provoke and that tends to show what they are like as art objects. Aesthetics then (following this intention) would not be viewed as a discipline akin to art theory that wouldexamine the structure of the work of art, its peculiarities, conditions of arising, et cetera, all that attests either to its objectivity or subjectivity. Ranciere (...) underscores the special (in the style of Hegel and Romanticist philosophy) regime of thinking about art where the idea is not yet an idea, but is what is not yet being thought. In spite of the fact that Ranciere’s declarations refer to S. Freud’s theory of the unconscious that, in his opinion, is closely linked with the way of artistic thinking and possibly can be expressed in no other way but through the medium of artistic thinking. The same way refers to the basic concepts of Freud’s psychoanalysis including also the unconscious and the ideas on complexes, especially on the Oedipus complex. It is interesting that Ranciere compares the framework ofthe dramatic nature of Oedipus’ fate with the basic fluctuations of aesthetics and art and namely – just like Oedipus is also the one who experiences everything absolutely and is completely expressed in action so the character of aesthetics and art is hidden in the contradictions between activities and sufferings or action and passions. This theme just like the question of the extreme poles of understanding aesthetics – pleasure and pain is comparable with the question of the determination of aesthetics and also art that grasps human experience in figural bodily shapes because that is the way of discerning the thought that is not yet being thought, but is hidden in bodily or animated figures. This tradition or historical regime, I think, is not to be discovered as a rectilinear trajectory; it manifests itself in a contradictory and sporadic way, frequently as an interlude between crucial conclusions and an essential interest pointing towards the ambivalence of art that referring to the words of the early modernist poet Charles Baudelaire: “I am the wound and the knife” would mark these relationships between action and its effect that could also attest to the painful birth of the thought in the not thought yet or else the negative character of aistheton. (shrink)

When it comes to evaluating our own abilities and prospects, most people are subject to a distorting bias. We think that we are better – friendlier, more well-liked, better leaders, and better drivers – than we really are. Once we learn about this bias, we should ratchet down our self-evaluations to correct for it. But we don’t. That leaves us with an uncomfortable tension in our beliefs: we knowingly allow our beliefs to differ from the ones that we think are (...) supported by our evidence. We can mitigate the tension by waffling between two belief states: a reflective state that has been recalibrated to take into account our tendency to overrate ourselves, and a non-reflective state that has not. (shrink)

Say that an agent is "epistemically humble" if she is less than certain that her opinions will converge to the truth, given an appropriate stream of evidence. Is such humility rationally permissible? According to the orgulity argument : the answer is "yes" but long-run convergence-to-the-truth theorems force Bayesians to answer "no." That argument has no force against Bayesians who reject countable additivity as a requirement of rationality. Such Bayesians are free to count even extreme humility as rationally permissible.

There is a huge chasm between the notion of lawful determination that figures in fundamental physics, and the notion of causal determination that figures in the "folk physics" of everyday objects. In everyday life, we think of the behavior of an ordinary object as being determined by a small set of simple conditions. But in fundamental physics, no such conditions suffice to determine an ordinary object's behavior. What bridges the chasm is that fundamental physical laws make the folk picture of (...) the world approximately true in certain domains. How? In part, by entailing that many objects are approximately isolated from most of their environments. Dynamical laws yield this result only in conjunction with appropriate statistical assumptions about initial conditions. (shrink)

The ability to analyze arguments is critical for higher-level reasoning, yet previous research suggests that standard university education provides at best modest improvements in students’ analytical reasoning abilities. What techniques are most effective for cultivating these skills? Here we investigate the effectiveness of a 12-week undergraduate seminar in which students practice a software-based technique for visualizing the logical structures implicit in argumen- tative texts. Seminar students met weekly to analyze excerpts from contemporary analytic philosophy papers, completed argument visualization problem sets, (...) and received individualized feedback on a weekly basis. We found that Seminar students improved substantially more on LSAT Logical Reasoning test forms than Control students (d = .71, p < .001), suggesting that learning how to visualize arguments in the seminar led to large generalized improvements in students’ analytical reasoning skills. Moreover, blind scoring of final essays from Seminar students and Control students, drawn from a parallel lecture course, revealed large differences in favor of seminar students (d = 0.87, p = .005). Seminar students understood the arguments better, and their essays were more accurate and effectively structured. Taken together, these findings deepen our understanding of how visualizations support logical reasoning, and provide a model for improving analytical reasoning pedagogy. (shrink)

O artigo se propõe a refletir sobre a relação entre Estado, desenvolvimento no continente africano e pandemia da Covid-19. De caráter ensaístico, espera-se demonstrar que, além de simbolizarem o avanço da solidariedade africana vide integração como meio para a solução dos desafios africanos, as ações para mitigar o avanço da Covid-19 no continente africano, em verdade, refletem, em maior ou menor intensidade, o distanciamento do Estado africano com relação ao neoliberalismo. Para tal feito, a metodologia adotada será de abordagem qualitativa (...) e de caráter interpretativo, baseada na revisão da literatura e no uso de documentos oficiais, sendo o artigo estruturado, juntamente a essa introdução e as considerações finais, em mais três seções. Na primeira, buscaremos discorrer sobre as principais características da relação entre Estado e desenvolvimento econômico no continente africano durante a Guerra Fria. Em seguida, analisaremos o avanço do neoliberalismo e seus impactos na relação entre Estado e desenvolvimento nos países africanos. Por fim, na terceira seção o principal objetivo será destacar o modo de atuação dos países africanos na luta contra a pandemia da Covid-19. (shrink)

Head direction (HD) cells, abundant in the rat postsubiculum and anterior thalamic nuclei, fire maximally when the rat’s head is facing a particular direction. The activity of a population of these cells forms a distributed representation of the animal’s current heading. We describe a neural network model that creates a stable, distributed representation of head direction and updates that representation in response to angular velocity information. In contrast to earlier models, our model of the head direction system accurately tracks a (...) series of actual rat head rotations, and, using biologically plausible neurons, it fits the single-cell tuning curves of real HD cells recorded from rats executing those same rotations. The model makes neurophysiological predictions that can be tested using current technologies. (shrink)

Counter-intuitive consequences of both causal decision theory and evidential decision theory are dramatized. Each of those theories is thereby put under some pressure to supply an error theory to explain away intuitions that seem to favour the other. Because trouble is stirred up for both sides, complacency about Newcomb’s problem is discouraged.

1. A particle moves back and forth along a line, increasing in speed. Graph. 2. How many equivalence classes in Galilean spacetime are there for a particle that is at rest? A particle that is moving at a constant speed? Why are the previous two questions trick questions? 3. In Galilean spacetime, there is no such thing as absolute velocity. Is there such a thing as absolute acceleration? If not, why not? If so, describe a spacetime in which there is (...) no notion of absolute acceleration. Hint: to move from Aristotelian spacetime to Galilean spacetime, we got rid of the notion of absolute velocity by counting two graphs as equivalent if they differed by a shear transformation. Perhaps we can get rid of absolute acceleration with an analogous move? 4. Draw a two-dimensional Cartesian grid. Label the axes x and t, and mark a scale on these axes. Make the x axis the horizontal axis, and the t axis the vertical one. Pick two points that are not on the same vertical line. Name them Ann and Bob. Label each point with its x and t coordinates. (shrink)

Turing machine An idealized computing device attached to a tape, each square of which is capable of holding a symbol. We write a program (a nite binary string) on the tape, and start the machine. If the machine halts with string o written at a designated place on the tape.

Poza niepewnością co do tego, jaki jest świat, można być także niepewnym swojego przestrzennego lub czasowgo położenia w świecie. Celem artykułu jest postawienie problemu wynikającego z połączenia tych dwóch rodzajów niepewności, a następnie rozwiązanie go i wyciągnięcie dwóch lekcji z tego rozwiązania.

Explain how to represent claims about Turing machines (for example, claims of the form ”machine m halts on input i”) in the above language. The goal is a mechanical method for translating claims about TMs into arithmetical claims in a way that preserves truth value.

According to a typical skeptical hypothesis, the evidence of your senses has been massively deceptive. Venerable skeptical hypotheses include the hypotheses that you have been deceived by a powerful evil demon, that you are now having an incredibly detailed dream, and that you are a brain in a vat. It is obviously reasonable for you now to be confident that neither of the above hypotheses is true. Epistemologists have proposed many stories to explain why that is reasonable. One theory is (...) that those hypotheses are inherently much less plausible than the hypothesis that your senses are basically reliable. Another theory is that you currently don’t believe any of those hypotheses, and that you need no justification to continue in that disbelief, given that your current beliefs cohere properly. A third theory is that —given that your senses are working properly—your sensory experiences themselves justify you in believing propositions such as the proposition that you have hands. Neo is given very good evidence that some skeptical hypothesis is true. He rightly becomes doubtful that his senses are or have been trustworthy. In fact, he becomes confident of a particular hypothesis: that AI’s created the Matrix, etc. But this is just one of many types of hypotheses that might account for his experiences. These types include. (shrink)

Este trabajo analiza el discurso de la cooperación técnica brasileña para la promoción del desarrollo en los países africanos, relacionándolo con el aumento significativo de las inversiones en las empresas brasileñas en el continente. La estabilidad política, junto con el éxito de la economía brasileña, ha favorecido una participación más activa en la coordinación de la política mundial y el aumento de la cooperación con los países de Sudamérica, pero sobre todo en países africanos como Mozambique. Los países africanos se (...) han convertido en importantes receptores de la cooperación técnica en el marco del discurso de la solidaridad internacional y la necesidad de compensación de la deuda histórica. Sin embargo, si este discurso se propaga a la desvinculación de los intereses económicos en un momento de crisis económica mundial, es imprescindible reflexionar sobre las limitaciones del discurso desinteresado. En este sentido, a partir de la documentación producida por la diplomacia brasileña y las posiciones de Brasil y Mozambique en la escena internacional, el objetivo de este artículo es analizar el discurso brasileño, especialmente en Mozambique, en contra de la lógica capitalista de producción impregnada de un escenario de crisis internacional. (shrink)

It is bad news to find out that one's cognitive or perceptual faculties are defective. Furthermore, it’s not always transparent how one ought to revise one's beliefs in light of such news. Two sorts of news should be distinguished. On the one hand, there is news that a faculty is unreliable -- that it doesn't track the truth particularly well. On the other hand, there is news that a faculty is anti-reliable -- that it tends to go positively wrong. These (...) two sorts of news call for extremely different responses. We provide accounts of these responses, and prove bounds on the degree to which one can reasonably count oneself as mistaken about a given subject matter. (shrink)

The rejection of an infinitesimal solution to the zero-fit problem by A. Elga ([2004]) does not seem to appreciate the opportunities provided by the use of internal finitely-additive probability measures. Indeed, internal laws of probability can be used to find a satisfactory infinitesimal answer to many zero-fit problems, not only to the one suggested by Elga, but also to the Markov chain (that is, discrete and memory-less) models of reality. Moreover, the generalization of likelihoods that Elga has (...) in mind is not as hopeless as it appears to be in his article. In fact, for many practically important examples, through the use of likelihoods one can succeed in circumventing the zero-fit problem. 1 The Zero-fit Problem on Infinite State Spaces 2 Elga's Critique of the Infinitesimal Approach to the Zero-fit Problem 3 Two Examples for Infinitesimal Solutions to the Zero-fit Problem 4 Mathematical Modelling in Nonstandard Universes? 5 Are Nonstandard Models Unnatural? 6 Likelihoods and Densities A Internal Probability Measures and the Loeb Measure Construction B The (Countable) Coin Tossing Sequence Revisited C Solution to the Zero-fit Problem for a Finite-state Model without Memory D An Additional Note on ‘Integrating over Densities’ E Well-defined Continuous Versions of Density Functions. (shrink)

Argues for the "thirder" solution to the Sleeping Beauty puzzle. The argument turns on an analogy with a variant case, in which a coin-toss on Monday night determines whether one's memories of Monday are permanently erased, or merely suspended in such a way that they will return some time after one wakes up on Tuesday.

In this paper I show that Elga’s argument for a restricted principle of indifference for self-locating belief relies on the kind of mistaken reasoning that recommends the ‘staying’ strategy in the Monty Hall problem.

Adam Elga takes the Sleeping Beauty example to provide a counter-example to Reflection, since on Sunday Beauty assigns probability 1/2 to H, and she is certain that on Monday she will assign probability 1/3. I will show that there is a natural way for Bas van Fraassen to defend Reflection in the case of Sleeping Beauty, building on van Fraassen’s treatment of forgetting. This will allow me to identify a lacuna in Elga’s argument for 1/3. I will then (...) argue, however, that not all is well with Reflection: there is a problem with van Fraassen’s treatment of forgetting. Ultimately I will agree with Elga’s 1/3 answer. David Lewis maintains that the answer is 1/2; I will argue that cases of forgetting can be used to show that the premiss of Lewis’s argument for 1/2 is false. (shrink)

Elga (2010) argues that no plausible decision rule governs action with imprecise credences. I follow Moss (2015a) in claiming that the solution to Elga’s challenge is found in the philosophy of mind, not in devising a special new decision rule. Moss suggests that in decision situations that involve imprecise credences, we must identify with a precise credence, but she says little about identification. By reflecting on the common conception of identification and on what is necessary for Moss’s solution (...) to succeed, I argue that identifying with a precise credence is fundamentally accepting (in the sense of Bratman 1992; Cohen 1989) a proposition about probabilities. The norm on action with imprecise credences is then a special case of the general norm on action and acceptance. I delineate a number of attractive features of this position. (shrink)

It is well known that classical, aka ‘sharp’, Bayesian decision theory, which models belief states as single probability functions, faces a number of serious difficulties with respect to its handling of agnosticism. These difficulties have led to the increasing popularity of so-called ‘imprecise’ models of decision-making, which represent belief states as sets of probability functions. In a recent paper, however, Adam Elga has argued in favour of a putative normative principle of sequential choice that he claims to be borne (...) out by the sharp model but not by any promising incarnation of its imprecise counterpart. After first pointing out that Elga has fallen short of establishing that his principle is indeed uniquely borne out by the sharp model, I cast aspersions on its plausibility. I show that a slight weakening of the principle is satisfied by at least one, but interestingly not all, varieties of the imprecise model and point out that Elga has failed to motivate his stronger commitment. (shrink)

This paper examines three accounts of the sleeping beauty case: an account proposed by Adam Elga, an account proposed by David Lewis, and a third account defended in this paper. It provides two reasons for preferring the third account. First, this account does a good job of capturing the temporal continuity of our beliefs, while the accounts favored by Elga and Lewis do not. Second, Elga’s and Lewis’ treatments of the sleeping beauty case lead to highly counterintuitive (...) consequences. The proposed account also leads to counterintuitive consequences, but they’re not as bad as those of Elga’s account, and no worse than those of Lewis’ account. (shrink)

Adam Elga (Philosophers’ Imprint, 10(5), 1–11, 2010) presents a diachronic puzzle to supporters of imprecise credences and argues that no acceptable decision rule for imprecise credences can deliver the intuitively correct result. Elga concludes that agents should not hold imprecise credences. In this paper, I argue for a two-part thesis. First, I show that Elga’s argument is incomplete: there is an acceptable decision rule that delivers the intuitive result. Next, I repair the argument by offering a more (...) elaborate diachronic puzzle that is more difficult for imprecise Bayesians to avoid. (shrink)

Since Elga published his “Self-locating belief and the Sleeping Beauty problem,” there has been an intense debate about which credence between 1/2 and 1/3 Beauty should assign to (H) the coin’s landing heads, when she is awakened on Monday. The Halfers claim that she ought to assign 1/2 to H at that moment. The Thirders argue that she ought to assign 1/3 to H then. Meanwhile, Pettigrew defended a new chance-credence coordination principle, called the “Evidential Temporal Principle” (ETP), in (...) a recent edition of his book. In this paper, I provide a novel argument against the Halfer view and a partial defense of the Thirder view, respectively based on ETP. In addition, I generalize ETP to what I call the “Evidential Centered Principle,” which links one’s credences in centered propositions with their objective chances. (shrink)

Adam Elga has presented an anti-thermodynamic process as a counterexample to Lewis’s default semantics for counterfactuals. The outstanding reaction of Jonathan Schaffer and Boris Kment is revisionary. It sacrifices Lewis’s aim of defining causation in terms of counterfactual dependence. Lewis himself suggested an alternative: «counter-entropic funnybusiness» should make for dissimilarity. But how is this alternative to be spelled out? I discuss a recent proposal: include special science laws, among them the laws of thermodynamics. Although the proposal fails, it serves (...) to uncover the limits of Elga’s example. (shrink)

Elga : 1–10, 2010) has argued that, even when no particular subjective probability is required by one’s evidence, perfectly rational people will have sharp subjective probabilities. Otherwise, they would be rationally permitted to knowingly turn down some sure gains. I argue that it is likewise true that, even when we do not possess enough practical reasons for a sharp evaluation, perfectly rational people will have sharp subjective values. Those who would be most inclined to reject this argument are those (...) who claim that we are rationally required by either our beliefs that objective values are unsharp or by our own ‘real’ values to have unsharp subjective values. Regarding the former claim, I show that we need not believe that all objective values are sharp to rationally have unsharp subjective values. Regarding the latter claim, I conclude that sharpened subjective values must be ‘real’ because otherwise perfect rationality would be impossible in principle. (shrink)

Adam Elga has argued that holders of imprecise credences fall prey to missed arbitrages, so that rational credences should be sharp. A decision rule proposed by Rohan Sud, Forward Looking, enables imprecise Bayesians to sidestep missed arbitrages and other ``bad books'' in isolated fixed-evidence binary betting sequences such as those of Elga. We show that Forward Looking imprecise Bayesians are committed to a bad book of bets when faced with a particular 3-bet variable-evidence binary betting sequence.

Adam Elga [Elga 2010] argues that no principle of rationality leads from unsharp probabilities to decisions. He concludes that a perfectly rational agent does not have unsharp probabilities. This paper defends unsharp probabilities. It shows how unsharp probabilities may ground rational decisions.

Adam Elga [Elga 2010] argues that no principle of rationality leads from unsharp probabilities to decisions. He concludes that a perfectly rational agent does not have unsharp probabilities. This paper defends unsharp probabilities. It shows how unsharp probabilities may ground rational decisions.

Since the publication of Elga's seminal paper in 2000, the Sleeping Beauty paradox has been the source of much discussion, particularly in this journal. Over the past few decades the Everettian interpretation of quantum mechanics 1 has also been much debated. There is an interesting connection between the way these two topics raise issues about subjective probability assignments.This connection is often alluded to, but as far as we know Peter J. Lewis's ‘Quantum Sleeping Beauty’ is the first attempt to (...) examine it explicitly. Lewis claims that the two debates are not independent: to be specific, he argues that accepting the Everettian interpretation of quantum mechanics requires you to be a ‘halfer’ about Sleeping Beauty, in opposition to the more widely accepted ‘thirder’ solution.This paper will argue that Lewis is wrong. Everettians do not have to be halfers. It is perfectly cogent to be both an Everettian and a thirder. (shrink)