How do we know what's (metaphysically) possible and impossible? Arguments from Kripke and Putnam suggest that possibility is not merely a matter of (coherent) conceivability/imaginability. For example, we can coherently imagine that Hesperus and Phosphorus are distinct objects even though they are not possibly distinct. Despite this apparent problem, we suggest, nevertheless, that imagination plays an important role in an adequate modal epistemology. When we discover what is possible or what is impossible, we generally exploit important connections between what is (...) possible and what we can coherently imagine. We can often come to knowledge of metaphysical modality a priori. (shrink)

Natural kind terms have exercised philosophical fancy ever since Kripke, in Naming and Necessity, claimed them to be rigid designators. He there drew attention to the peculiar, name-like behavior of a family of prima facie loosely related general terms of ordinary English: terms such as ‘water’, ‘tiger’, ‘heat’, and ‘red’. Just as for ordinary proper names, Kripke argued that such terms cannot be synonymous with any of the definite descriptions ordinary speakers associate with them. Rather, the name-like behavior of these (...) so-called natural kind terms is to be explained, just as in in the case of proper names, by the doctrine of rigid designation. And as a consequence of thus extending the notion of rigid designation to general terms, he famously endorsed the claim that so-called ‘theoretical identifications’, i.e. statements like (1) Water is H2O, are necessary, if true. (shrink)

forthcoming in R. Cameron, B. Hale and A. Hoffmann (ed.s), The Logic, Epistemology and Metaphysics of Modality, Oxford University Press. Presents a concept-grounding account of modal knowledge.

I argue that you can have a priori knowledge of propositions that neither are nor appear necessarily true. You can know a priori contingent propositions that you recognize as such. This overturns a standard view in contemporary epistemology and the traditional view of the a priori, which restrict a priori knowledge to necessary truths, or at least to truths that appear necessary.

In this essay, I argue that a proper understanding of the historicity of love requires an appreciation of the irreplaceability of the beloved. I do this through a consideration of ideas that were first put forward by Robert Kraut in “Love De Re” (1986). I also evaluate Amelie Rorty's criticisms of Kraut's thesis in “The Historicity of Psychological Attitudes: Love is Not Love Which Alters Not When It Alteration Finds” (1986). I argue that Rorty fundamentally misunderstands Kraut's Kripkean analogy, and (...) I go on to criticize her claim that concern over the proper object of love should be best understood as a concern over constancy. This leads me to an elaboration of the distinct senses in which love can be seen as historical. I end with a further defense of the irreplaceability of the beloved and a discussion of the relevance of recent debates over the importance of personal identity for an adequate account of the historical dimension of love. (shrink)

Identity theorists make claims like ‘pain = C-fibre stimulation’. These claims must be necessary if true, given that terms like ‘pain’ and ‘C-fibre stimulation’ are rigid. Yet there is no doubt that such claims appear contingent. It certainly seems that there could have been C-fibre stimulation without pains or vice versa. So identity theorists owe us an explanation of why such claims should appear contingent if they are in fact necessary.

A primary goal of this chapter is to highlight neglected epistemic parallels between dualism and physicalism. Both dualist and physicalist arguments employ a combination of empirical data and armchair reflection; both rely on considerations stemming from how we conceptualize certain phenomena; and both aim to establish views that are compatible with scientific results but go well beyond the deliverances of empirical science. -/- I begin the chapter by fleshing out the distinctive commitments of dualism, in a way that illuminates the (...) interplay of epistemic and metaphysical elements within the dualist position. Section 2 outlines two influential arguments for dualism and explains how dualists defend those arguments from key criticisms. Sections 3 and 4 examine the most powerful objections to dualism: that it is inferior to physicalism as regards the theoretical virtue of simplicity, and that it cannot explain mental causation. I show that each of these objections to dualism depends on substantial assumptions that cannot be empirically justified. The objection from mental causation additionally rests on an ambitious assumption about how we conceptualize physical phenomena. Section 5 briefly reviews how epistemic considerations inform arguments on both sides of this debate. (shrink)

An exploration of the details of counterpart theory, and some applications of the view. In Chapter 1, I set out the view and clarify the most important features: that the counterpart relation is a context dependent similarity relation, and that individuals are world-bound entities. I then set out what I take to be the most promising methods of filling in important details. Chapter 2 is a discussion of an alternative view, lump theory. I attempt to distinguish lump theory from counterpart (...) theory, and argue that several attempt to do so fail. Chapter 3 is an attempt to apply counterpart theory for individuals to properties. I attempt to stay as close to the standard view as possible, but find it necessary to modify the world-bound condition. I suggest a version of property counterpart theory that overcomes the obstacles I have identified. The final chapter is a discussion of a recent attempt to apply counterpart theory to the comparativist view of quantitative properties. I argue that an attempt to rely on counterpart theory to overcome an objection is unsuccessful. (shrink)

Recent third person approaches to thought experiments and conceptual analysis through the method of surveys are motivated by and motivate skepticism about the traditional first person method. I argue that such surveys give no good ground for skepticism, that they have some utility, but that they do not represent a fundamentally new way of doing philosophy, that they are liable to considerable methodological difficulties, and that they cannot be substituted for the first person method, since the a priori knowledge which (...) is our object in conceptual analysis can be acquired only from the first person standpoint. (shrink)

Frege's theory of indirect contexts and the shift of sense and reference in these contexts has puzzled many. What can the hierarchy of indirect senses, doubly indirect senses, and so on, be? Donald Davidson gave a well-known 'unlearnability' argument against Frege's theory. The present paper argues that the key to Frege's theory lies in the fact that whenever a reference is specified (even though many senses determine a single reference), it is specified in a particular way, so that giving a (...) reference implies giving a sense; and that one must be 'acquainted' with the sense. It is argued that an indirect sense must be 'immediately revelatory' of its reference. General principles for Frege's doctrine of sense and reference are sated, for both direct and indirect quotation, to be understood iteratively. I also discuss Frege's doctrine of tensed and first person statements in the light of my analysis. The views of various other authors are examined. The conclusion is to ascribe to Frege an implicit doctrine of acquaintance similar to that of Russell. (shrink)

It is often thought that endowing a demonstrative with a Fregean sense leaves no room for maintaining that it is also a rigid designator. In addition, some philosophers claim that indexicals - surely the paradigms of singular reference - pose a serious threat to the Fregean sense/ reference approach as they do not comply with the view that singular terms have Fregean senses. In this paper I argue that neither of these is true.

Disposition ascription has been discussed a good deal over the last few decades, as has the revisionary metaphysical view of ordinary, persisting objects known as 'fourdimensionalism'. However, philosophers have not merged these topics and asked whether four-dimensional objects can be proper subjects of dispositional predicates. This paper seeks to remedy this oversight. It argues that, by and large, four-dimensional objects are not suited to take dispositional predicates.

Abstract In this paper I criticise a recent account of fictional discourse proposed by Nathan Salmon. Salmon invokes abstract artifacts as the referents of fictional names in both object- and meta-fictional discourse alike. He then invokes a theory of pretence to forge the requisite connection between object-fictional sentences and meta-fictional sentences, in virtue of which the latter can be assigned appropriate truth-values. I argue that Salmon's account of pretence renders his appeal to abstract artifacts as the referents of fictional names (...) in object-fictional discourse explanatorily redundant. I further argue that his account is therefore no improvement over those he criticises, thus leaving his own account unmotivated. (shrink)

It may be that all that matters for the modalities, possibility and necessity, is the object named by the proper name, not which proper name names it. An influential defender of this view is Saul Kripke. Kripke’s defense is criticized in the paper.

Once symbolized by a burning armchair, experimental philosophy has in recent years shifted away from its original hostility to traditional methods. Starting with a brief historical review of the experimentalist challenge to traditional philosophical practice, this chapter looks at research undercutting that challenge, and at ways in which experimental work has evolved to complement and strengthen traditional approaches to philosophical questions.

Timothy Williamson has defended the claim that any philosophically satisfying conception of modality that encompasses possible worlds semantics (PWS) commits us to the Barcan Formula. His argument depends on the assumption that the domain of what there is (the domain of the actual world) has to be identified with the domain D(@), where @ is the index or possible world that in PWS represents , or stands for , the actual world. I work out an interpretation of the relation between (...) PWS and possible worlds terminology that makes it plausible to reject that assumption. (shrink)

There seems to be a distinction between primary and secondary properties; some philosophers defend the view that properties like colours and values are secondary, while others criticize it. The distinction is usually introduced in terms of essence; roughly, secondary properties essentially involve mental states, while primary properties do not. In part because this does not seem very illuminating, philosophers have produced different reductive analyses in modal terms, metaphysic or epistemic. Here I will argue, firstly, that some well-known examples fail, and (...) also that there are deep reasons why such approaches should do so. Secondly, I will argue that it is acceptable to remain satisfied with the non-reductive account in terms of essence. To that end, I will indicate how such an explication could be put to use to support the claim that properties like colours and values are secondary. In a series of recent writings, Kit Fine has argued that essence cannot be reductively analysed in modal terms. Fine offers some examples to motivate his claim. I suggest that the primary/secondary distinction constitutes a philosophically interesting illustration. (shrink)

Abstract It is widely assumed that the meaning of at least some types of expressions involves more than their reference to objects, and hence that there may be co-referential expressions which differ in meaning. It is also widely assumed that ?syntax does not suffice for semantics?, i.e. that we cannot account for the fact that expressions have semantic properties in purely syntactical or computational terms. The main goal of the paper is to argue against a third related assumption, namely that (...) what is responsible for a difference in meaning between co-referential expressions is the computational difference in the cognitive functioning of the expressions. ?Intentional aspects? of expressions?those features which their meanings involve in addition to reference?cannot be syntacticized, since they are individuated not in terms of any cognitive feature, but rather in terms of those properties of the referents through which the expressions refer to them, and cognitive features cannot determine such properties in exactly the same sense as they cannot determine reference. (shrink)

Abstract In this paper I propose a mereological account of ordinary macro-events of experience that is based on two central features of these entities, namely their spatio-temporal character, and their status as things that belong to event-kinds. I argue that, from the perspective of descriptive metaphysics, these features must be incorporated in the analysis of the part-whole relations of events, and I show the steps involved in achieving this task. Furthermore, I argue that the program initiated here is quite promising: (...) the analysis of event-part that I propose stands up quite well against the more serious objections, and the apparatus I provide for the mereological conditions of events can be easily modified to yield similar conditions for material objects. (shrink)

Is the world internally connected by a web of necessary connections or is everything loose and independent? Followers of David Hume accept the latter by upholding Hume’s Dictum, according to which there are no necessary connections between distinct existences. Roughly put, anything can coexist with anything else, and anything can fail to coexist with anything else. Hume put it like this: “There is no object which implies the existence of any other if we consider these objects in themselves.” Since Hume’s (...) day, Hume’s Dictum has played a major role in philosophy, especially in contemporary metaphysics. In ruling out necessary connections, Hume’s Dictum implies that causal relations and the laws of nature are contingent. It makes other demands on our metaphysics of science as well; for example, it places restrictions on our metaphysics of counterfactuals, dispositions, and explanation. The principle has applications in other areas too. Hume’s Dictum places constraints on our theories of abstract objects and moral properties. For example, Hume’s Dictum rules out the view that moral properties are distinct from, but necessarily connected to, non-moral properties. While Hume’s Dictum is a prominent principle in metaphysics, few Humeans have defended the principle at length. It is assumed more often than it is argued for. As a result, Hume’s Dictum no longer enjoys the reputation it once did. It’s common to hear complaints about the lack of arguments in support of Hume’s Dictum. Moreover, philosophers are increasingly willing to defend views that are at odds with Hume’s Dictum. A striking example of this is the recent explosion of interest in views that take causal relations and the laws of nature to be necessary. Humeans can no longer afford to be complacent. An extended defense of Hume’s Dictum is called for, and that’s what this dissertation aims to offer. This dissertation has three parts. In the first part, I lay out some preliminaries and offer a precise formulation of Hume’s Dictum. In the second part, I develop three arguments in favor of Hume’s Dictum. In the final part, I defend Hume’s Dictum against objections. (shrink)

RésuméPaul Boghossian soutient contre Wittgenstein que le normativisme au sujet de la logique et des mathématiques est incompatible avec le fait de tenir les énoncés logiques et mathématiques pour vrais et que le normativisme entraîne une régression indue. Je soutiens, pour ma part, que le normativisme n'entraîne pas une telle régression, parce que les normes peuvent être implicites et que le normativisme peut bien être «factualiste» si l'on rejette ce que Rockney Jacobsen appelle le «cognitivisme sémantique». Je tiens en outre (...) que la position de Boghossian repose sur la façon trompeuse dont il découpe le terrain conceptuel. (shrink)

This book is about the idea that some true statements would have been true no matter how the world had turned out, while others could have been false. It develops and defends a version of the idea that we tell the difference between these two types of truths in part by reflecting on the meanings of words. It has often been thought that modal issues—issues about possibility and necessity—are related to issues about meaning. In this book, the author defends the (...) view that the analysis of meaning is not just a preliminary to answering modal questions in philosophy; it is not merely that before we can find out whether something is possible, we need to get clear on what we are talking about. Rather, clarity about meaning often brings with it answers to modal questions. In service of this view, the author analyzes the notion of necessity and develops ideas about linguistic meaning, applying them to several puzzles and problems in philosophy of language. Meaning and Metaphysical Necessity will be of interest to scholars and advanced students working in metaphysics, philosophy of language, and philosophical logic. [See my homepage for a sample chapter.]. (shrink)

The subject matter of this paper is the view that it is correct, in an absolute sense, to believe a proposition just in case the proposition is true. I take issue with arguments in support of this view put forward by Nishi Shah and David Velleman.

I argue that an identity theorist can successfully resist a Kripkean modal argument by employing what I call a metaconceptual move. Furthermore, by showing how this move fails to apply straightforwardly to Chalmers' argument, I clarify the nature of the threat presented by Chalmers and how it differs from a Kripkean modal argument.

Este artigo é uma breve introdução à filosofia da linguagem. Ele se concentra nos problemas que surgem a partir de dois conceitos centrais: referência e significado. Em particular, o foco central é no problema fundacional da referência e no problema descritivo do significado, assim como a relação entre eles. Embora esta de modo algum seja uma introdução exaustiva ao tema, muitos conceitos centrais são clarificados, como por exemplo teoria da referência, termo singular, termo geral, teoria do significado, composicionalidade, conteúdo, significado (...) linguístico, implicatura conversacional, vagueza, etc. Espera-se que sirva como um primeiro contato com a disciplina, principalmente voltado a estudantes de filosofia, filosofia da linguagem e áreas afins. (shrink)

In this chapter, I revisit the issue of the explanatory gap that is supposed to open when considering identity statements between physical and mental phenomena. I show that the question asked in the original formulation of the explanatory gap was this: ʻwhy this phenomenal character, rather than any other, is attached to this physiological process?ʼ I argue that this question can be answered, because there is a natural fit between the phenomenal character of experiences and their functional roles. For example, (...) pains feel inherently unpleasant, and that explains why they cause avoidance behaviour, and the felt location and intensity of pain indicates the location and extent of damage to the body. I discuss some other possible gaps in our understanding the relationship between the mental and the physical, and conclude that the fit between functional role and phenomenal character goes a long way, though probably not the whole way, to closing the explanatory gap. (shrink)

Human dignity is one of the key concepts of our ethical evaluations, in politics, in biomedicine, as well as in everyday life. In moral philosophy, however, human dignity is a source of intractable trouble. It has a number of characteristic features which apparently do not fit into one coherent ethical concept. Hence, philosophers tend to ignore or circumvent the concept. There is hope for a philosophically attractive conception of human dignity, however, given that one takes three crucial turns. The negative (...) turn: to start the inquiry with violations of human dignity. The inductive turn: to consider the whole range of applications of the concept of human dignity in different areas of ethics. And finally, the historical turn: to take into account the historical bonds between human dignity and traditional conceptions of dignity. Taken together they point in the direction of an understanding of human dignity as universal nobility. (shrink)

Timothy Williamson offers a reductive account of modal knowledge in terms of knowledge of counterfactual conditionals. The account is developed in a broader context of defending two more general theses regarding the subject matter and methodology of philosophy. My primary focus in this paper is Williamson’s account of modal knowledge. I argue (1) that his account of modal knowledge does not support his more general theses regarding the subject matter and methodology of philosophy; (2) that the two central claims of (...) his account of knowledge of counterfactuals are rooted in unsubstantiated empirical assumptions; and (3) that his argument in support of the conclusion that modal knowledge is a special case of counterfactual knowledge rests on three errors: conflating logical reduction and epistemological reduction, a misguided appeal to cognitive economy, and incorrectly locating what needs to be explained by an account of modal knowledge. (shrink)

Can experimental philosophy help us answer central questions about the nature of moral responsibility, such as the question of whether moral responsibility is compatible with determinism? Specifically, can folk judgments in line with a particular answer to that question provide support for that answer. Based on reasoning familiar from Condorcet’s Jury Theorem, such support could be had if individual judges track the truth of the matter independently and with some modest reliability: such reliability quickly aggregates as the number of judges (...) goes up. In this chapter, however, I argue, partly based on empirical evidence, that although non-specialist judgments might on average be more likely than not to get things right, their individual likelihoods fail to aggregate because they do not track truth with sufficient independence. (shrink)

What is the relation between meaning and use? This chapter first defends a non-reductionist understanding of Wittgenstein’s suggestion that ‘the meaning of a word is its use in the language’; facts about meaning cannot be reduced to, or explained in terms of, facts about use, characterized non-semantically. Nonetheless, it is contended, facts about meaning do supervene on non-semantic facts about use. That supervenience thesis is suggested by comments of Wittgenstein’s and is consistent with his view of meaning and rule-following. Semantic (...) supervenience is then defended against two criticisms: first, John McDowell’s suggestion that the supervenience thesis falsifies the epistemology of meaning and fails to accommodate common-sense truths about meaning; second, a series of counter-examples proposed by Stephen Kearns and Ofra Magidor, who argue that worlds may differ semantically without differing non-semantically. It is argued that neither criticism is convincing: we should accept the thesis that semantic facts supervene on non-semantic facts. (shrink)

I present a new argument for the thesis that there is a necessarily existing, causally powerful entity—a necessary being. The outline of the argument is this: (i) necessarily, every beginning of a certain sort S (which I'll specify) can have a cause; (ii) a beginning to the existence of all non-necessarily existing things would be of sort S; (iii) such a beginning can obtain; (iv) such a beginning cannot be caused unless there is a necessary being; therefore, (v) there is (...) a necessary being. The argument uses a causal principle that is more modest than causal principles previously used in arguments for a necessary being. (shrink)

I give two arguments for the claim that all events which occur at the actual world and are such that they could be caused, are also such that they must actually be caused. The first argument is an improvement of a similar argument advanced by Alexander Pruss, which I show to be invalid. It uses Pruss’s Brouwer Analog for counterfactual logic, and, as a consequence, implies inconsistency with Lewis’s semantics for counterfactuals. While (I suggest) this consequence may not be objectionable, (...) the argument founders on the fact that Pruss’s Brouwer Analog has a clear counterexample. I thus turn to a second, “Lewisian” argument, which requires only an affirmation of one element of Lewis’s analysis of causation and one other, fairly weak possibility claim about the nature of wholly contingent events. The final section of the paper explains how both arguments escape objections from supposed indeterminacy in quantum physics. (shrink)

Relativized Metaphysical Modality (RMM: Murray and Wilson, 'Relativized metaphysical modality', Oxford Studies in Metaphysics, 2012; Murray, Perspectives on Modal Metaphysics, 2017) exploits 'two-dimensionalist' resources to metaphysical, rather than epistemological, ends: the second dimension offers perspective-dependence without contingency, diverting attacks on 'Classical' analyses of modals (in effect, analyses validating S5 and the Barcan Formulae). Here, we extend the RMM program in two directions. First, we harvest resources for RMM from Lewis's 1980 'Context--Index' (CI) framework: (a) the ban in CI on binding (...) into context-arguments (akin to Kaplan's 'monstrosity' ban) projects a bright line between perspective-dependence and contingency; and (b) CI-postulated connections among meaning, content, truth, argument-structure, context, and modality collectively generate a 'Generalized Humphrey Problem' for any non-Classical analysis (examples covered include appeals to accessibility, contingent domains, and counterpart relations). Second, we sharpen the tools of RMM-based metaphysical analysis, and extend their domain of coverage across familiar anomalies for Classical modals: we revisit earlier RMM-based bulwarks for S5 (against 'Chisholm's Paradox' for moderate flexibility of essence, and nomological necessitarianism); and we now similarly shore up the Barcan Formulae (against the apparent contingency of existence and nonexistence). (shrink)

I defend a one category ontology: an ontology that denies that we need more than one fundamental category to support the ontological structure of the world. Categorical fundamentality is understood in terms of the metaphysically prior, as that in which everything else in the world consists. One category ontologies are deeply appealing, because their ontological simplicity gives them an unmatched elegance and spareness. I’m a fan of a one category ontology that collapses the distinction between particular and property, replacing it (...) with a single fundamental category of intrinsic characters or qualities. We may describe the qualities as qualitative charactersor as modes, perhaps on the model of Aristotelian qualitative (nonsubstantial) kinds, and I will use the term “properties” interchangeably with “qualities”. The qualities are repeatable and reasonably sparse, although, as I discuss in section 2.6, there are empirical reasons that may suggest, depending on one’s preferred fundamental physical theory, that they include irreducibly intensive qualities. There are no uninstantiated qualities. I also assume that the fundamental qualitative natures are intrinsic, although physics may ultimately suggest that some of them are extrinsic. On my view, matter, concrete objects, abstract objects, and perhaps even spacetime are constructed from mereological fusions of qualities, so the world is simply a vast mixture of qualities, including polyadic properties (i.e., relations). This means that everything there is, including concrete objects like persons or stars, is a quality, a qualitative fusion, or a portion of the extended qualitative fusion that is the worldwhole. I call my view mereological bundle theory. (shrink)

I am going to argue for a robust realism about magnitudes, as irreducible elements in our ontology. This realistic attitude, I will argue, gives a better metaphysics than the alternatives. It suggests some new options in the philosophy of science. It also provides the materials for a better account of the mind’s relation to the world, in particular its perceptual relations.

This volume examines the limitations of mathematical logic and proposes a new approach to logic intended to overcome them. To this end, the book compares mathematical logic with earlier views of logic, both in the ancient and in the modern age, including those of Plato, Aristotle, Bacon, Descartes, Leibniz, and Kant. From the comparison it is apparent that a basic limitation of mathematical logic is that it narrows down the scope of logic confining it to the study of deduction, without (...) providing tools for discovering anything new. As a result, mathematical logic has had little impact on scientific practice. Therefore, this volume proposes a view of logic according to which logic is intended, first of all, to provide rules of discovery, that is, non-deductive rules for finding hypotheses to solve problems. This is essential if logic is to play any relevant role in mathematics, science and even philosophy. To comply with this view of logic, this volume formulates several rules of discovery, such as induction, analogy, generalization, specialization, metaphor, metonymy, definition, and diagrams. A logic based on such rules is basically a logic of discovery, and involves a new view of the relation of logic to evolution, language, reason, method and knowledge, particularly mathematical knowledge. It also involves a new view of the relation of philosophy to knowledge. This book puts forward such new views, trying to open again many doors that the founding fathers of mathematical logic had closed historically. (shrink)

The role of possible worlds in philosophy is hard to overestimate. Nevertheless, their nature and existence is very controversial. This is particularly serious, since their standard applications depend on there being sufficiently many of them. The paper develops an account of possible worlds on which it is particularly easy to believe in their existence: an account of possible worlds as pleonastic entities. Pleonastic entities are entities whose existence can be validly inferred from statements that neither refer to nor quantify over (...) them as a matter of conceptual necessity. Definitions are proposed that ensure that this is the case for possible worlds. (shrink)

It is common in various quarters of philosophy to derive philosophically significant conclusions from theories of reference. In this paper, we argue that philosophers should give up on such 'arguments from reference.' Intuitions play a central role in establishing theories of reference, and recent cross-cultural work suggests that intuitions about reference vary across cultures and between individuals within a culture (Machery et al. 2004). We argue that accommodating this variation within a theory of reference undermines arguments from reference.

: It is generally accepted that skeptical scenarios must be possible to raise legitimate skeptical doubt. I argue that if the possibility in question is supposed to be genuine metaphysical possibility, the skeptic's reasoning does not straightforwardly succeed. I first motivate the metaphysical possibility requirement on skeptical scenarios : it's a plausible position that several authors accept and that a family of prominent views—sensitivity, safety, relevant alternatives—are committed to. I argue that plausible constraints in modal epistemology show that justification for (...) believing that certain global skeptical scenarios are metaphysically possible rests on some justified beliefs about the external world, and that this undermines the skeptical argument. While there may still be local skeptical challenges, skeptics cannot appeal to the metaphysical possibility of skeptical scenarios to generate global external world skepticism. (shrink)