The Doomsday Argument and the Simulation Argument share certain structural features, and hence are often discussed together. Both are cases where reflecting on one’s location among a set of possibilities yields a counter-intuitive conclusion—in the first case that the end of humankind is closer than you initially thought, and in the second case that it is more likely than you initially thought that you are living in a computer simulation. Indeed, the two arguments do have some structural (...) similarities. But there are also significant disanalogies between the two arguments, and I argue that these disanalogies mean that the Simulation Argument succeeds and the Doomsday Argument fails. (shrink)

The Doomsday argument purports to show that the risk of the human species going extinct soon has been systematically underestimated. This argument has something in common with controversial forms of reasoning in other areas, including: game theoretic problems with imperfect recall, the methodology of cosmology, the epistemology of indexical belief, and the debate over so-called fine-tuning arguments for the design hypothesis. The common denominator is a certain premiss: the Self-Sampling Assumption. We present two strands of argument (...) in favor of this assumption. Through a series of thought experiments we then investigate some bizarre prima facie consequences – backward causation, psychic powers, and an apparent conflict with the Principal Principle. (shrink)

The Carter-Leslie Doomsday argument, as standardly presented, relies on the assumption that you have knowledge of your approximate birth rank. I demonstrate that the Doomsday argument can still be given in a situation where you have no knowledge of your birth rank. This allows one to reply to Bostrom's defense of the Doomsday argument against the refutation based on the idea that your existence makes it more likely that many observers exist.

If the human race comes to an end relatively shortly, then we have been born at a fairly typical time in the history of humanity; if trillions of people eventually exist, then we have been born in the first surprisingly tiny fraction of all people. According to the 'doomsday argument' of Carter, Leslie, Gott and Nielsen, this means that the chance of a disaster which would obliterate humanity is much larger than usually thought. But treating possible observers in (...) the same way as those who actually exist avoids this conclusion: our existence is more likely in a race which is long-lived, and this cancels out the doomsday argument, so that the chance of a disaster is only what one would ordinarily estimate. (shrink)

In a recent paper in this journal, Ken Olum attempts to refute the doomsday argument by appealing to the self–indication assumption (SIA) that your very existence gives you reason to think that there are many observers. Unlike earlier users of this strategy, Olum tries to counter objections that have been made against (SIA). We argue that his defence of (SIA) is unsuccessful. This does not, however, mean that one has to accept the doomsday argument (or the (...) other counter–intuitive results that flow from related thought–experiments). A developed theory of observation selection effects shows why the doomsday argument is inconclusive, and how one can consistently reject both it and (SIA). (shrink)

Inspired by anthropic reasoning behind Doomsday arguments, Nick Bostrom's Simulation Argument says: people who think advanced civilisations would run many fully-conscious simulated minds should also think they're probably simulated minds themselves. However, Bostrom's conclusions can be resisted, especially by sympathisers with Doomsday or anthropic reasoning. This paper initially offers a posterior-probabilistic ‘Doomsday lottery’ argument against Bostrom's conclusions. Suggestions are then offered for deriving anti-simulation conclusions using weaker assumptions. Anti-simulation arguments herein use more robust reference classes (...) than Bostrom's argument, require no Principles of Indifference, abide better by the total evidence requirement, and yet use empirically plausible priors and likelihoods. However, while Doomsday arguments are probabilistically, epistemically and metaphysically stronger than the Simulation Argument, anthropic reasoning can refrain from embracing either. (shrink)

In our current unstable world, nuclear warfare, climate crises, and techno nihilism are three perilous clouds hovering over an anxious humanity. In this article I examine our current state of affairs with regard to the imminent risk of nuclear holocaust, rapid climate emergencies destroying the planet, and the cultural and political consequences of emerging technologies on the fate of civilization. In the wake of innumerable existential threats to the future of our world, I revisit the plausibility of the Doomsday (...) Argument, which predicts the end of human existence. (shrink)

The Doomsday Argument says we should increase our subjective probability that Doomsday will occur once we take into account how many humans have lived before us. One objection to this conclusion is that we should accept the Self-Indication Assumption (SIA): Given the fact that you exist, you should (other things equal) favor hypotheses according to which many observers exist over hypotheses on which few observers exist. Nick Bostrom argues that we should not accept the SIA, because it (...) can be used without knowledge of birth rank. Bradley Monton tries to construct a Doomsday Argument without knowledge of birth rank. I argue that Monton fails. The argument he constructs has implicit knowledge of birth rank and it is this knowledge that does the work. Furthermore, I argue that provided we dont have certain specific information about the future, the Doomsday Argument requires knowledge of birth rank. (shrink)

This chapter provides a brief version of the mathematician Brandon Carter's “doomsday argument”, a probabilistic argument that attempts to predict the future lifetime of the human race given an estimate of the total number of humans born thus far. It challenges Carter's argument by stating the crucial point that we ought (until we find enough contrary evidence) to try to see ourselves as “fairly ordinary” inside the various classes into which we fall ‐ bearing in mind, (...) naturally, that in some cases there might be tradeoffs to be made because being more ordinary inside one class might involve being less ordinary inside another. Even if humans were statistically very unusual among all observers scattered through space and time, observers falling into vastly many different species, there might still be nothing too odd in being a human rather than a member of some other intelligent species. (shrink)

A recent paper by Korb and Oliver in this journal attempts to refute the Carter-Leslie Doomsday argument. I organize their remarks into five objections and show that they all fail. Further efforts are thus called upon to find out what, if anything, is wrong with Carter and Leslie's disturbing reasoning. While ultimately unsuccessful, Korb and Oliver's objections do however in some instances force us to become clearer about what the Doomsday argument does and doesn't imply.

In a recent paper in this journal, Ken Olum attempts to refute the Doomsday argument by appealing to the self-indication assumption, the idea that your very existence gives you reason to think that there are many observers. In contrast to earlier refutation attempts that use this strategy, Olum confronts and try to counter some of the objections that have been made against SIA. We argue that his defense of SIA is unsuccessful. This does not, however, mean that one (...) has to accept the Doomsday argument. A developed theory of observation selection effects shows why the Doomsday argument is inconclusive and how one can consistently reject both it and SIA. (shrink)

A recent paper by Korb and Oliver in this journal attempts to refute the Carter-Leslie Doomsday argument. I organize their remarks into five objections and show that they all fail. Further efforts are thus called upon to find out what, if anything, is wrong with Carter and Leslie’s disturbing reasoning. While ultimately unsuccessful, Korb and Oliver’s objections do however in some instances force us to become clearer about what the Doomsday argument does and doesn’t imply.

Leslie’s doomsday argument purports to show that the likelihood of the human race perishing soon is greater than we think. The probability we attach to it, based on our estimate of the chance of various calamities which might bring extinction about (a nuclear holocaust, an ecological disaster, etc.), should be adjusted as follows. If the human race were to survive for a long time, we, livingnow, would be atypical. So our living now increases the probability that the human (...) race will end shortly. In this paper, I criticize some attempts to rebut the argument, and present my own. To facilitate the analysis, I consider a structurally similar problem, the “ShootingRoom.”. (shrink)

If the most familiar overlapping interpretation of Everettian quantum mechanics is correct, then each of us is constantly splitting into multiple people. This consequence gives rise to the quantum doomsday argument, which threatens to draw crippling epistemic consequences from EQM. However, a diverging interpretation of EQM undermines the quantum doomsday argument completely. This appears to tell in favour of the diverging interpretation. But it is surprising that a metaphysical question that is apparently underdetermined by the physics (...) should be settled by purely epistemological considerations; and I argue that the positive case for divergence based on the quantum doomsday effect is ultimately unsuccessful. I discuss how some influential treatments of Everettian confirmation handle the quantum doomsday puzzle, and suggest that it can most satisfyingly be resolved via a naturalistic approach to the metaphysics of modality. (shrink)

English translation of a paper originally pupblished in French in the Canadian Journal of Philosophy under the title 'Comment l'urne de Carter et Leslie se déverse dans celle de Hempel'. In this paper, I present firstly a solution to Hempel's Problem. I recall secondly the solution to the Doomsday Argument described in my previous Une Solution pour l'Argument de l'Apocalypse (Canadian Journal of Philosophy 1998-2) and remark that both solutions are based on a similar line of reasoning. (...) I show thirdly that the Doomsday Argument can be reduced to the core of Hempel's Problem. (shrink)

Rarely does philosophy produce empirical predictions. The Doomsday argument is an important exception. From seemingly trivial premises it seeks to show that the risk that humankind will go extinct soon has been systematically underestimated. Nearly everybody's first reaction is that there must be something wrong with such an argument. Yet despite being subjected to intense scrutiny by a growing number of philosophers, no simple flaw in the argument has been identified.

Carter and Leslie's Doomsday Argument maintains that reflection upon the number of humans born thus far, when that number is viewed as having been uniformly randomly selected from amongst all humans, past, present and future, leads to a dramatic rise in the probability of an early end to the human experiment. We examine the Bayesian structure of the Argument and find that the drama is largely due to its oversimplification.

I argue that the Doomsday argument fails because it fails to take into account the lesson of the Sleeping Beauty puzzle.

John Leslie has published an argument that our own birth rank among all who have lived can be used to make inferences about all who will ever live, and hence about the expected survival time for the human race. It is found to be shorter than usually supposed. The assumptions underpinning the argument are criticized, especially the unwarranted one that the argument's sampling is equiprobable from among all who ever live. A mathematical derivation shows that Leslie's (...) class='Hi'>argument is correct only if there exists a correlation of our birth rank to the event of doomsday. Such correlation is highly improbable. (shrink)

A refutation of the doomsday argument is offered. Through a simple thought experiment analysed in Bayesian terms the fallacy is shown to be the assumption that a currently living person represents a random sample from the population of all persons who will ever have existed. A more general version of the counter argument is then given. Previous arguments that purport to answer this concern are also addressed. One result is determining criteria for the applicability of time sampling (...) arguments, i.e., under what conditions can a specific instant in time be regarded as a random sample from a time span. Given this new understanding, the incredible consequences of the doomsday and related arguments evaporate. (shrink)

A refutation of the doomsday argument is offered. Through a simple thought experiment analysed in Bayesian terms the fallacy is shown to be the assumption that a currently living person represents a random sample from the population of all persons who will ever have existed. A more general version of the counter argument is then given. Previous arguments that purport to answer this concern are also addressed. One result is determining criteria for the applicability of time sampling (...) arguments, i.e., under what conditions can a specific instant in time be regarded as a random sample from a time span. Given this new understanding, the incredible consequences of the doomsday and related arguments evaporate. (shrink)

I present a new case in which the Doomsday Argument runs afoul of epistemic intuition much more strongly than before. This leads to a dilemma: in the new case either DA is committed to unacceptable counterintuitiveness and belief in miracles, or else it is irrelevant. I then explore under what conditions DA can escape this dilemma. The discussion turns on several issues that have not been much emphasised in previous work on DA: a concern that I label trumping; (...) the degree of uncertainty about relevant probability estimates; and the exact sequence in which we integrate DA and empirical concerns. I conclude that only given a particular configuration of these factors might DA still be of interest. (shrink)

claim that his thought experiment shows that a currently living person is not a random sample is refuted. His thought experiment is reduced to a probability model, and is shown to be identical to one previously developed by Dieks. The status of the Doomsday Argument is left unresolved, since Dieks's refutation attempt is disputed in the literature.

ABSTRACT Brandon Carter's anthropic principle reminds us that observers are most likely to find themselves in the spatiotemporal regions containing most of them. One should tend to prefer theories which make one's own observed spatiotemporal position fairly ordinary. This could much increase the estimated likelihood that our technological civilisation was not the very first in a universe which would include hugely many such civilisations. Similarly, which is the Carter‐Leslie ‘doomsday argument’, it could much increase the estimated likelihood that (...) you and I are not in the earliest 0.01%, for instance, of all humans who will ever have lived—as we would be if the human race survived for long even at its present size, let alone if it colonised the galaxy. With the aid of thought‐experiments, the article defends this argument against many objections. Other thought‐experiments suggest, though, that the argument is weaker if the world is radically indeterministic. In this case, it perhaps indicates only that we should not be highly confident in humankind's long survival, because high confidence would be equivalent to saying that any indeterminism would be unlikely to be relevant. (shrink)

Paying strict attention to Brandon Carter's several published renditions of anthropic reasoning, we present a ``nutshell'' version of the Doomsday argument that is truer to Carter's principles than the standard balls-and-urns or otherwise ``naive Bayesian'' versions that proliferate in the literature. At modest cost in terms of complication, the argument avoids commitment to many of the half-truths that have inspired so many to rise up against other toy versions, never adopting posterior outside of the convex hull of (...) one's prior distribution over the ``true chance'' of Doom. The hyper-pessimistic position of the standard balls-and-urn presentation and the hyper-optimistic position of naive self-indicators are seen to arise from dubiously extreme prior distributions, leaving room for a more satisfying and plausible intermediate solution. (shrink)

George Sowers tries to refute the Doomsday argument on grounds that true random sampling requires all possible samples to be equally probable the time when the sample is taken. Yet the Doomsday argument does not rely on true random sampling. It presupposes random sampling only in a metaphorical sense. After arguing that Sowers’ critique fails, I outline my own view on the matter, which is that the Doomsday argument is inconclusive and that by developing (...) a theory of observation selection effects one can show why that is so. (shrink)

Physicist J. Richard Gott uses the Copernican principle that “we are not special” to make predictions about the future lifetime of the human race, based on how long the human race has been in existence so far. We show that the predictions which can be derived from Gott’s argument are less strong than one might be inclined to believe, that Gott’s argument illegitimately assumes that the human race will not last forever, that certain versions of Gott’s argument (...) are incompatible with Bayesian conditionalization, and that Gott’s argument is self-refuting. -/- *****Note: For Bradley Monton's up-to-date thoughts on Gott's argument, see his _Philosophical Quarterly_ paper co-authored with Brian Kierland, "How To Predict Future Duration from Present Age".*****. (shrink)

I discuss two versions of the doomsday argument. According to ``Gott's Line'',the fact that the human race has existed for 200,000 years licences the predictionthat it will last between 5100 and 7.8 million more years. According to ``Leslie'sWedge'', the fact that I currently exist is evidence that increases the plausibilityof the hypothesis that the human race will come to an end sooner rather than later.Both arguments rest on substantive assumptions about the sampling process thatunderlies our observations. These sampling (...) assumptions have testable consequences,and so the sampling assumptions themselves must be regarded as empirical claims.The result of testing some of these consequences is that both doomsday argumentsare empirically disconfirmed. (shrink)

Suppose various observers are divided randomly into two groups, a large and a small. Not knowing into which group anyone has been sent, each can have strong grounds for believing in being in the large group, although recognizing that every observer in the other group has equally powerful reasons for thinking of this other group as the large one. Justified belief can therefore be observer-relative in a rather paradoxical way. Appreciating this allows one to reject an intriguing new objection against (...) Brandon Carter's 'doomsday argument'. Carter encourages us to doubt that we are among only the first hundredth, say, or first millionth, of all humans who will ever have existed. He thereby reinforces whatever reasons we may have for suspecting that, unless we take great care, the human race will not survive long. Admittedly his argument is weakened if our world is indeterministic, so that there is no suitably guaranteed 'fact of the matter' of how many humans will ever have existed. But even then, it can caution us against believing that a lengthy future for humankind 'is as good as determined'. Of all the objections the argument has yet faced, the new one is the most interesting. (shrink)

In this paper, I present a solution to the Doomsday argument based on a third type of solution, by contrast to, on the one hand, the Carter-Leslie view and, on the other hand, the Eckhardt et al. analysis. I begin by strengthening both competing models by highlighting some variations of their original models, which renders them less vulnerable to several objections. I then describe a third line of solution, which incorporates insights from both Leslie and Eckhardt’s models and (...) fits more adequately with the human situation corresponding to DA. I argue then that this two-sided analogy casts new light on the reference class problem. This leads finally to a novel formulation of the argument that could well be more plausible than the original one. (shrink)

In this paper, I present a solution to the Doomsday argument based on a third type of solution, by contrast to, on the one hand, the Carter-Leslie view and, on the other hand, the Eckhardt et al. analysis. I begin by strengthening both competing models by highlighting some variations of their original models, which renders them less vulnerable to several objections. I then describe a third line of solution, which incorporates insights from both Leslie and Eckhardt’s models and (...) fits more adequately with the human situation corresponding to DA. I argue then that this two-sided analogy casts new light on the reference class problem. This leads finally to a novel formulation of the argument that could well be more plausible than the original one. (shrink)

A recent book of mine defends three distinct varieties of immortality. One of them is an infinitely lengthy afterlife; however, any hopes of it might seem destroyed by something like Brandon Carter's 'doomsday argument' against viewing ourselves as extremely early humans. The apparent difficulty might be overcome in two ways. First, if the world is non-deterministic then anything on the lines of the doomsday argument may prove unable to deliver a strongly pessimistic conclusion. Secondly, anything on (...) those lines may break down when an infinite sequence of experiences is in question. (shrink)

This paper considers the argument according to which, because we should regard it as a priori very unlikely that we are among the most important people who will ever exist, we should increase our confidence that the human species will not persist beyond the current historical era, which seems to represent a crucial juncture in human history and perhaps even the history of life on earth. The argument is a descendant of the Carter-Leslie Doomsday Argument, but (...) I show that it does not inherit the crucial flaw in its immediate ancestor. Nonetheless, we are not forced to follow the argument where it leads if we instead significantly decrease our confidence that we can affect the long-run future of humanity. GPI Working Paper No. 1-2019. (shrink)

Lewis’s Principal Principle says that one should usually align one’s credences with the known chances. In this paper I develop a version of the Principal Principle that deals well with some exceptional cases related to the distinction between metaphysical and epistemic modal­ity. I explain how this principle gives a unified account of the Sleeping Beauty problem and chance-­based principles of anthropic reasoning. In doing so, I defuse the Doomsday Argument that the end of the world is likely to (...) be nigh. GPI Working Paper No. 8-2021. (shrink)

We give an analysis of the Monty Hall problem purely in terms of confirmation, without making any lottery assumptions about priors. Along the way, we show the Monty Hall problem is structurally identical to the Doomsday Argument.

In a recent article, John Leslie has defended the intriguing Carter-Leslie ‘Doomsday Argument’ (Philosophy, January 2000). I argue that an essential presupposition of the argument—that ‘the case of one's name coming out of [an] urn is sufficiently similar to the case of being born into the world’—engenders, in turn, a parallel ‘Ussherian Corollary’. The dubiousness of this Corollary, coupled with independent considerations, casts doubt upon the Carter-Leslie presupposition, and hence, dooms the Doomsday argument.

This paper attempts three tasks in relation to Carter and Leslie's Doomsday Argument. First, it criticises Timothy Chambers' 'Ussherian Corollary', a striking but unsuccessful objection to standard Doomsday arguments. Second, it reformulates the Ussherian Corollary as an objection to Bradley Monton's variant Doomsday and Nick Bostrom's Simulation Argument. Finally, it tries to diagnose the epistemic/metaphysical problems facing Doomsday-related arguments.1.

Attribué à Brandon Carter, l' argument de l'Apocalypse Doomsday Argument , soit DA, dans ce qui suit) a été décrit par John Leslie (1992). On peut formuler ainsi cet argument. Soit A l'événement: l'Apocalypse se produira avant l'an 2150 ; et B l'événement: l'Apocalypse ne se produira pas avant 2150 . Soit également Z l'événement: j'ai connu les années 1990 . On peut par ailleurs estimer à 40 milliards le nombre d'humains ayant existé depuis la naissance (...) de l'humanité, jusqu'à notre époque: soit H1996 un tel nombre. On peut ainsi admettre, de manière raisonnable, qu'un humain sur dix, dans le cas de l'événement.. (shrink)

The heuristic value of Pylyshyn's cognitive impenetrability theory is questioned in this commentary, mainly because, as it stands, the key argument cannot be challenged empirically. Pylyshyn requires unambiguous evidence for an effect of cognitive states on early perceptual mechanisms, which is impossible to provide because we can only infer what might happen at these earlier levels of processing on the basis of evidence collected at the post-perceptual stage. Furthermore, the theory that early visual processes cannot be modified by cognitive (...) states implies that it is totally pointless to try to investigate interactions between consciousness and neurosensory processes. (shrink)

One might think that since life here on Earth has survived for nearly 4 Gyr (Gigayears), such catastrophic events must be extremely rare. Unfortunately, such an argument is flawed, giving us a false sense of security. It fails to take into account the observation selection effect [6, 7] that precludes any observer from observing anything other than that their own species has survived up to the point where they make the observation. Even if the frequency of cosmic catastrophes were (...) very high, we should still expect to find ourselves on a planet that had not yet been destroyed. The fact that we are still alive does not even seem to rule out the hypothesis that the average cosmic neighborhood is typically sterilized by vacuum decay, say, every 10000 years, and that our own planet has just been extremely lucky up until now. (shrink)

Following on from Nick Bostrom's discussion of the Doomsday argument, Alasdair Richmond considers how anthropic reasoning can lead from Doomsday to some odd conclusions about computation and our place in reality.

J. Richard Gott III (1993) has used the “Copernican principle” to derive a probability density function for the total longevity of any phenomenon, based solely on the phenomenon’s past longevity. John Leslie (1996) and others have used an apparently similar probabilistic argument, the “Doomsday Argument,” to claim that conventional predictions of longevity must be adjusted, based on Bayes’ Theorem, in favor of shorter longevities. Here I show that Gott’s arguments are flawed and contradictory, but that one of (...) his conclusions—his delta t formula—is mathematically equivalent to Laplace’s famous (and notorious) ‘rule of succession’; moreover, Gott’s delta t formula is a plausible worst-case (if one favors greater longevity) bound in some contexts. On the other hand, the Doomsday Argument is fallacious: the argument’s Bayesian formalism is stated in terms of total duration, but all attempted real-life applications of the argument—with one exception, an application by Gott 1994—actually plug in prior probabilities for future duration; moreover, the Self-Sampling Assumption, an essential premise of the Doomsday Argument, is contradicted by the prior information in all known real-life cases. But rejecting the Doomsday Argument does not entail rejecting the possibility of learning about the future from the past. Applying the work of Bruce M. Hill (1968, 1988, 1993) and Frank P.A. Coolen (1998, 2006) in the field of non-parametric predictive inference, I propose and defend an alternative methodology for quantifying how past longevity of any phenomenon does provide evidence for future longevity. In so doing, I identify an objective standard by which to choose among counting time intervals, counting population, or counting any other measure of past longevity in predicting future longevity. This methodology forms the basis of a calculus of induction. (shrink)

Several philosophical problems are based on an analogy between a real situation and a probabilistic model. Such problems are based on urn analogies. The present dissertation aims to describe and implement a methodology oriented towards the resolution of philosophical problems based on an urn analogy. This methodology is based on the use of the n-universes. To this end, I describe first the n-universes in a detailed way. I also discuss the difficulties of the theory of n-universes related to the demultiplication (...) of the criteria and to the relation one/many between the objects and a given criterion. On the one hand, I present an application of the framework of n-universes to the Doomsday argument and to the problems recently appeared in the literature in keeping with the Doomsday argument. My concern is also with showing how the application of the framework of n-universes to several problems and thought experiments related to the Doomsday argument helps clarifying the problem data and making disappear the associated ambiguity. I present then an analysis of the following problems related to the Doomsday argument: the two urn case, God's Coin Toss, the Sleeping Beauty Problem, the Presumptuous Philosopher, Lazy Adam, and the Shooting-Room Paradox. I present lastly a solution to the Doomsday argument, based on a third route, by contrast to two types of solutions classically described. On the other hand, I present an application of the framework of n-universes to Goodman's paradox. I replace first Goodman's statement in the framework of n-universes. I propose then a solution to the paradox, based on a distinction between two different modelizations of Goodman's statement in two structurally different n-universes. (shrink)

The point of this note is to compare the Doomsday Argument to the Simulation Argument. The latter, I maintain, is a better argument than the former.

The Doomsday argument and anthropic reasoning are two puzzling examples of probabilistic confirmation. In both cases, a lack of knowledge apparently yields surprising conclusions. Since they are formulated within a Bayesian framework, they constitute a challenge to Bayesianism. Several attempts, some successful, have been made to avoid these conclusions, but some versions of these arguments cannot be dissolved within the framework of orthodox Bayesianism. I show that adopting an imprecise framework of probabilistic reasoning allows for a more adequate (...) representation of ignorance in Bayesian reasoning and explains away these puzzles. (shrink)

To ascertain the rational credences for the epistemic agents in the famous cases of self-locating belief, one should model the processes by which those agents acquire their evidence. This approach, taken by Darren Bradley (Phil. Review 121, 149–177) and Joseph Halpern (Ergo 2, 195–206), is immensely reasonable. Nevertheless, the work of those authors makes it seem as if this approach must lead to such conclusions as the Doomsday argument being correct, and that Sleeping Beauty should be a halfer. (...) I argue that this is due to an implicit existential bias: it is assumed that the first step in those processes is the determination that the agent in question must necessarily exist. It is much more reasonable to model that determination as contingent and a result of other, earlier, steps in the process. This paper offers such alternative models. They imply an endorsement of what has mockingly been called “presumptuous” reasoning, and a massive shift of credences in favor of (1) the existence of a multiverse and (2) the Everettian interpretation of quantum mechanics. (shrink)