Brains in Vats

Some modern cosmological models predict the appearance of Boltzmann Brains: observers who randomly fluctuate out of a thermal bath rather than naturally evolving from a low-entropy Big Bang. A theory in which most observers are of the Boltzmann Brain type is generally thought to be unacceptable, although opinions differ. I argue that such theories are indeed unacceptable: the real problem is with fluctuations into observers who are locally identical to ordinary observers, and their existence cannot be swept under the rug (...) by a choice of probability distributions over observers. The issue is not that the existence of such observers is ruled out by data, but that the theories that predict them are cognitively unstable: they cannot simultaneously be true and justifiably believed. (shrink)

This paper reassesses the case against Evidential Externalism, the thesis that one's evidence fails to supervene on one's non-factive mental states, focusing on two objections to Externalism due by Nicholas Silins: the armchair access argument and the supervenience argument. It also examines Silins's attempt to undermine the force of one major source of motivation for Externalism, namely that the rival Internalist picture of evidence is implicated in some central arguments for scepticism. While Silins concludes that the case against Evidential Externalism (...) is surprisingly strong, reassessing the arguments supports the opposite conclusion; the objections to Externalism are weak, and for all Silins has shown it may well have unmatched advantages when it comes to resisting scepticism. (shrink)

In this paper, I offer reasons for thinking that two prominent sceptical arguments in the literature – the underdetermination-based sceptical argument and the closure-based sceptical argument – are less philosophically interesting than is commonly supposed. The underdetermination-based argument begs the question against a non-sceptic and can be dismissed with little fanfare. The closure-based argument, though perhaps not question-begging per se, does rest upon contentious assumptions that a non-sceptic is under no pressure to accept.

According to the idealist, facts about phenomenal experience determine facts about the physical world. Any such view must account for illusions: cases where there is a discrepancy between the physical world and our experiences of it. In this paper, I critique some recent idealist treatments of illusions before presenting my own preferred account. I then argue that, initial impressions notwithstanding, it is actually the realist who has difficulties properly accounting for illusions.

The paper defends Cartesian skepticism by an argument relying on internalism and infallibilism. It argues that this sort of skepticism gives the best explanation of our intuitions and ordinary epistemic practices.

Going about our daily lives in an orderly manner requires us, once we are aware of them, to dismiss many metaphysical possibilities. We take it for granted that we are not brains in vats, or living in the Matrix, or in an extended dream. Call these things that we take for granted “anti-skeptical assumptions”. What should a reflective agent who believes these things think of these beliefs? For various reasons, it can seem that we do not have evidence for such (...) anti-skeptical assumptions. Are anti-skeptical assumptions, then, beliefs that one may rationally hold without evidence for them – indeed, even in the face of a positive judgment that one lacks evidence for them? I survey and criticize some prominent answers to this question, and then offer a positive view that blends externalism about evidence with a mild, qualified kind of pragmatism. The view I offer aims to do justice to the sense that anti-skeptical assumptions are evidentially groundless while also maintaining that one cannot rationally believe something that one judges oneself to lack sufficient evidence for. (shrink)

Cartesian arguments for global skepticism about the external world start from the premise that we cannot know that we are not in a Cartesian scenario such as an evil-demon scenario, and infer that because most of our empirical beliefs are false in such a scenario, these beliefs do not constitute knowledge. Veridicalist responses to global skepticism respond that arguments fail because in Cartesian scenarios, many or most of our empirical beliefs are true. Some veridicalist responses have been motivated using verificationism, (...) externalism, and coherentism. I argue that a more powerful veridicalist response to global skepticism can be motivated by structuralism, on which physical entities are understood as those that play a certain structural role. I develop the structuralist response and address objections. (shrink)

I will argue that cases of massive deception, such as New Evil Demon cases, as well as one-off cases of local deception present challenges to views according to which epistemic reasons, epistemic warrant, epistemic rationality or epistemic norms are factive. In doing so, I will argue is that proponents of a factive turn in epistemology should observe important distinctions between what are often simply referred to as ‘bad cases.’ Recognizing epistemologically significant differences between deception cases raises serious challenges for those (...) who deny a central role for non-factive aspects of epistemology. (shrink)

Here, I shall be examining the viability of a Moorean response to the Argument from Ignorance; i.e., one that tries to rebut the argument by denying its first premise that we cannot have knowledge that we are not BIVs. After first explicating the Argument from Ignorance in detail, I then go on to try and motivate this approach by critically examining two alternative approaches to dealing with radical scepticism: closure-denial, and attributer contextualism. Finding them wanting, I then turn to a (...) Moorean 'argument from knowledge', and diagnose why as it stands such an approach is ineffective, before going on to explore whether one can wed such an argument to an externalist framework in order to provide a more satisfying answer to the question of how one can know the denials of sceptical hypotheses, one that does not simply beg the question against the sceptic. Finding such a neo-Moorean approach to be initially promising, I then conclude by arguing that ultimately it winds up saving knowledge simpliciter only at the cost of losing rationally-grounded knowledge to the sceptic's grasp, and such a result is highly unpalatable. (shrink)

Radical skepticism relies on the hypothesis that one could be completely cut off from the external world. In this paper, I argue that this hypothesis can be rationally motivated by means of a conceivability argument. Subsequently, I submit that this conceivability argument does not furnish a good reason to believe that one could be completely cut off from the external world. To this end, I show that we cannot adequately conceive scenarios that verify the radical skeptical hypothesis. Attempts to do (...) so fall prey to one or another of three pitfalls: they end up incomplete, reveal a deep contradiction or recreate a non-skeptical hypothesis. I use these results to improve upon Pritchard’s recent attempt at undercutting radical skepticism. (shrink)

Epistemological disjunctivism is a philosophical theory that has received special attention in the recent years. Particularly because it has been seen by many as a way of renewing discussions that range from the nature of justification of our daily beliefs to the possibility of unveiling the structure of the problem of radical skepticism and of responding to it. Duncan Pritchard is one of the authors who have offered a particular view of disjunctivism and ways of conceiving of disjunctivist treatments to (...) such questions. His work has as its main source of inspiration the seminal work of John McDowell. In this paper, I present a way of understanding the problem ofradicalskepticism and the mannerin which epistemological disjunctivism aimsto offer solutionsto it. In orderto do that, I present McDowell’s general proposal and discuss in which way his account differs from Pritchard’s own disjunctivism. At the end, I try to show how Pritchard’s approach tries to respond to radical skepticism not only by appealing to a disjunctivist reading of our epistemic position, but also by offering a revision of our structure of reasons. (shrink)

In this paper, I argue that, if transcendental arguments are to proceed from premises that are acceptable to the skeptic, the Transcendental Premise, according to which “X is a metaphysically necessary condition for the possibility of Y,” must be grounded in considerations of conceivability and possibility. More explicitly, the Transcendental Premise is based on what Szabó Gendler and Hawthorne call the “conceivability-possibility move.” This “inconceivability-impossibility” move, however, is a problematic argumentative move when advancing transcendental arguments for the following reasons. First, (...) from “S cannot conceive of P” it doesn’t necessarily follow that P is inconceivable. Second, from “P is inconceivable” it doesn’t necessarily follow that P is metaphysically impossible. Third, rather than block skeptical doubts, the conceivability-possibility move introduces skeptical doubts. For these reasons, transcendental arguments fail to deliver on their promise to overcome skeptical doubts. (shrink)

In this paper, I argue that arguments from skeptical hypotheses for external world skepticism derive their support from a skeptical argument from the distinction between appearance and reality. This skeptical argument from the appearance/reality distinction gives the external world skeptic her conclusion without appealing to skeptical hypotheses and without assuming that knowledge is closed under known entailments. If this is correct, then this skeptical argument from the appearance/reality distinction poses a new skeptical challenge that cannot be resolved by denying skeptical (...) hypotheses or knowledge closure. (shrink)

Tim Button explores the relationship between minds, words, and world. He argues that the two main strands of scepticism are deeply related and can be overcome, but that there is a limit to how much we can show. We must position ourselves somewhere between internal realism and external realism, and we cannot hope to say exactly where.

Within the framework of the epistemological debate on disagreement, this paper aims to examine the sceptical thesis that holds that, if it is impossible to rationally choose among two excluding positions, the only sensible or rational thing to do is to suspend judgement. The idea that ordinary life does not constitute the source of scepticism is presented, which rules out real disagreement between epistemic pairs as its foundation. Sceptical scenes differ ontologically from everyday scenes, without such ontological difference entailing an (...) epistemic difference, since epistemic practices do not vary from one sceptical scene to other types of scenes. (shrink)

According to epistemic internalism, the only facts that determine the justificational status of a belief are facts about the subject’s own mental states, like beliefs and experiences. Externalists instead hold that certain external facts, such as facts about the world or the reliability of a belief-producing mechanism, affect a belief’s justificational status. Some internalists argue that considerations about evil demon victims and brains in vats provide excellent reason to reject externalism: because these subjects are placed in epistemically unfavorable settings, externalism (...) seems unable to account for the strong intuition that these subjects’ beliefs are nonetheless justified. I think these considerations do not at all help the internalist cause. I argue that by appealing to the anti-individualistic nature of perception, it can be shown that skeptical scenarios provide no reason to prefer internalism to externalism. (shrink)

The problem of philosophical skepticism relates to the difficulty involved in underwriting the claim that we know anything of spatio-temporal reality. It is often claimed, in fact, that proper philosophical scrutiny reveals quite the opposite from what common sense suggests. Knowledge of external reality is thought to be even quite obviously denied to us as a result of the alleged fact that we all fail to know that certain skeptical scenarios do not obtain. A skeptical scenario is one in which (...) we have neurological occurrences just like any normal situation in which we actually perceive spatio-temporal objects, but where we are deceived in some sense as a result of the manipulation of our brains from some outside source. In this work I attempt to address the problem of philosophical skepticism by claiming that most of us are able to come to know plenty about external reality, since we can come to realize that a certain philosophical theory of perception is correct. The theory I have in mind is what I call a non-cognitive theory of perception. According to this view, perceptual experience is defined by continuous, sensitive behavioral interaction with spatio-temporal objects of the appropriate size, shape, hardness, speed, etc. Knowing that this theory of perception is correct is equivalent to knowing that we know plenty about external reality. This is ultimately because by knowing that a non-cognitive theory of perception is true, we know that any skeptical scenario must fail to obtain. The structure of the work proceeds by first discussing the significance of the problem of philosophical skepticism in some detail. Chapter 1 lays out how the problem does indeed forcefully arise if it is conceded that we fail to know that the skeptical scenarios fail to obtain. Chapter 2 develops the sort of view of our epistemological situation that falls out of accepting without qualification that the problem exists. Chapter 3 examines and criticizes certain popular responses to the skeptical problem. The main goal of these first three preliminary chapters is to indicate that once it is admitted that we fail to know that the skeptical scenarios fail to obtain, the problem of philosophical skepticism forcefully presents itself. Chapter 4, however, attacks the idea that we fail to know that the skeptical scenarios fail to obtain. In this chapter I argue that this idea is wedded to the position that a certain theory of perception is correct. The theory in question is what I call a conjunctive theory of veridical experience. According to this view, normal experience of spatio-temporal objects occurs when a subject has a certain perceptual experience, and that experience also happens to match up with and/or be satisfied by what is really the case. Only when a theory of this sort is assumed, I argue, is the claim that we fail to know that the skeptical scenarios fail to obtain found to be obvious. In chapter 5 I argue that, in fact, a non-cognitive theory, rather than a conjunctive theory, is the correct view to maintain. In the final chapter 6 I develop the epistemological position that falls out of accepting a non-cognitive theory. (shrink)

It is received wisdom that the skeptic has a devastating line of argument in the following. You probably think, he says, that you know that you have hands. But if you knew that you had hands, then you would also know that you were not a brain in a vat, a brain suspended in fluid with electrodes feeding you perfectly coordinated impressions that are generated by a supercomputer, of a world that looks and moves just like this one. You would (...) know you weren’t in this state if you knew you had hands, since having hands implies you are no brain in a vat. You obviously don’t know you’re not a brain in a vat, though—you have no evidence that would distinguish that state from the normal one you think you’re in. Therefore, by modus tollens, you don’t know you have hands. At least, the skeptic has a devastating argument, it is thought, if we grant him closure of knowledge under known implication, which many of us are inclined to do: roughly, if you know p, and you know that p implies q, then you know q. (shrink)

The most prominent arguments for scepticism in modern epistemology employ closure principles of some kind. To begin my discussion of such arguments, consider Simple Knowledge Closure (SKC): (SKC) (Kxt[p] ∧ (p → q)) → Kxt[q].1 Assuming its truth for the time being, the sceptic can use (SKC) to reason from the two assumptions that, firstly, we don’t know ¬sh and that, secondly, op entails ¬sh to the conclusion that we don’t know op, where ‘op’ and ‘sh’ are shorthand for ‘ordinary (...) proposition’ and ‘sceptical hypothesis’ respectively. (SKC), however, fails for familiar reasons: since knowledge entails belief (KB), we can derive the falsity (F) from (SKC) by hypothetical syllogism, and thus reduce (SKC) to absurdity: (KB) Kxt[p] → Bxt[p]. (F) (Kxt[p] ∧ (p → q)) → Bxt[q]. (shrink)

This article offers a novel sceptical argument that the sensitivity-contextualist must say is sound; moreover, she must say that the conclusion of thisargument is true at ordinary standards. The view under scrutiny has it that in different contexts knowledge-attributing sentences express different propositions, propositions which differ in the stretch of worlds across which the subject is required to track the truth. I identify the underlying reason for the sceptical result and argue that it makes sensitivity-contextualism irremediably flawed. Contextualists, I conclude, (...) should abandon sensitivity for some other piece of epistemic machinery.Cet article présente un nouvel argument en faveur du scepticisme que les tenants du contextualisme sensoriel doivent reconnaître comme valide; qui plus est, ils doivent admettre que les conclusions de cet argument sont vraies selon des critères standards. J’examine la position selon laquelle, dans différents contextes, les formules visant à désigner un contenu de connaissance expriment différentespropositions, propositions qui diffèrent les unes des autres dans la série des mondes au sein desquels le sujet est à la recherche de la vérité. J’identifie la raison sur laquelle se fonde le constat sceptique et soutient qu’il fait du contextualisme sensoriel une position irrémédiablement défaillante. Je conclue en proposant que les tenants de cette position devraient abandonner la sensation à la faveur d’autres composantes des rouages épistémiques. (shrink)

Die klassische bikategoriale Ontologie von Substanzen und Akzidentien ist für die Festlegung der Strukturen menschlichen und tierischen Verhaltens nicht hinreichend, da die Umwelten dieses Verhaltens sich nicht in dieses klassische System einfügen. Wir bieten dementsprechend den Grundriß einer Theorie der besonderen Gebilde, die die Alltagswelten menschlicher und tierischer Verhalten konstituieren. Die Ausgangsüberlegung ist die folgende, Wir sind alle (Schau)spieler, und diese brauchen eine Bühne. Unsere Bühne ist die jeweilige Umwelt, in der wir leben und handeln. Der Terminus ‘Umwelt’ wird hierbei (...) in Analogie zu Husserls Begriff der Lebenswelt verwendet. Er bezeichnet dementsprechend einen strukturierten Teil der Welt, in den sich ein Lebewesen, z.B. ein Mensch, einpaßt. Die Umwelt ist, wenn man so will, demnach die Bühne, auf welcher sich unser Verhalten abspielt. Der Versuch, das Wesen solcher Umwelten ontologisch festzulegen, bringt allerdings ein schwieriges Problem mit sich - ein Problem so alt wie Platons Höhlengleichnis und so neu wie gegenwärtige Reflexionen amerikanischer Philosophen zur Metaphysik der virtuellen Realität und zum Gedankenexperiment des Gehirns im Tank. Es gibt nämlich in manchen Fällen grobe Inkonsistenzen zwischen (1) der Umwelt, wie wir sie uns gerade vorstellen, und (2) der Umwelt als Bestandteil der wirklichen Welt. Das Problem, zwischen diesen beiden Umweltklassen einen Ausgleich zu finden, wird im letzten Teil des Aufsatzes behandelt. (shrink)

Hillary Putnam has famously argued that we can know that we are not brains in a vat because the hypothesis that we are is self-refuting. While Putnam's argument has generated interest primarily as a novel response to skepticism, his original use of the brain in a vat scenario was meant to illustrate a point about the "mind/world relationship." In particular, he intended it to be part of an argument against the coherence of metaphysical realism, and thus to be part of (...) a defense of his conception of truth as idealized rational acceptability. Putnam's conclusions about the scenario are, however, actually out of line with central and plausible aspects of his own account of the relationship between our minds and the world. Reflections on semantics give us no compelling reason to suppose that claims like "I am a brain in a vat" could not turn out to be true. (shrink)

Crispin Wright hat die bislang beste Rekonstruktion von Putnams Beweis gegen die skeptische Hypothese vom Gehirn im Tank vorgelegt. Aber selbst in Wrights Fassung hat der Beweis einen Mangel: Er wird mithilfe eines Prädikates wie z.B. "Tiger" geführt und funktioniert nur, wenn man sich darauf verlassen kann, dass es Tiger wirklich gibt. Aber die Skeptikerin bestreitet, über die Existenz von Tigern bescheid zu wissen. Das Problem lässt sich dadurch beheben, dass man den Beweis – statt mit dem extensionalen Begriff der (...) Referenz (wie bei Wright) – mit Intensionen führt. Zudem sollte der Beweis transzendental laufen, also einzig und allein auf den sprachlichen Voraussetzungen beruhen, die auch die Skeptikerin zur Formulierung ihrer Tank-Hypothese benötigt. -/- The best reconstruction of Putnam's brain-in-a-vat argument is due to Crispin Wright. But even Wright's version of the argument is not convincing. It employs predicates such as 'tiger' and reaches the conclusion only if we can rely upon the existence of tigers; and the skeptic disputes our knowledge regarding tigers. The problem is not insuperable: The argument must be run, not with the extensionalistic notion of reference (as in Wright's version), but with intensions. Furthermore, the argument should have a transcendental form; it should exclusively rely on conditions that are needed by the skeptic for formulating her own position. (shrink)

Are we perhaps in the "matrix", or anyway, victims of perfect and permanent computer simulation? No. The most convincing—and shortest—version of Putnam's argument against the possibility of our eternal envattment is due to Crispin Wright (1994). It avoids most of the misunderstandings that have been elicited by Putnam's original presentation of the argument in "Reason, Truth and History" (1981). But it is still open to the charge of question-begging. True enough, the premisses of the argument (disquotation and externalism) can be (...) formulated and defended without presupposing external objects whose existence appears doubtful in the light of the very skeptical scenario which Putnam wants to repudiate. However, the argument is only valid if we add an extra premiss as to the existence of some external objects. In order to avoid circularity, we should run the argument with external objects which must exist even if we are brains in a vat, e.g. with computers rather than with trees. As long as the skeptic is engaged in a discussion of the brain-in-a-vat scenario, she should neither deny the existence of computers nor the existence of causal relations; for if she does, she is in fact denying that we are brains in a vat. (shrink)

Failure to recognize the "realistic" motivations for Putnam's commitment to internal realism has led to a widely shared misunderstanding of Putnam's arguments against metaphysical realism. Realist critics of these arguments frequently offer rebuttals that fail to confront his arguments. Simply put, Putnam's arguments --the brains in a vat argument as well as the model-theoretic argument -- are "reductios" that are intended to show that "metaphysical realism itself is not sufficiently realistic". If that claim can be substantiated then Putnam can go (...) on to argue that his own view is, by comparison, more realistic than metaphysical realism. (shrink)