Two lines of investigation into the nature of mental content have proceeded in parallel until now. The first looks at thoughts that are attributable to collectives, such as bands' beliefs and teams' desires. So far, philosophers who have written on collective belief, collective intentionality, etc. have primarily focused on third-personal attributions of thoughts to collectives. The second looks at de se, or self-locating, thoughts, such as beliefs and desires that are essentially about oneself. So far, philosophers who have written on (...) the de se have primarily focused on de se thoughts of individuals. This paper looks at where these two lines of investigations intersect: collective de se thoughts, such as bands' and teams' beliefs and desires that are essentially about themselves. There is a surprising problem at this intersection: the most prominent framework for modeling de se thoughts, the framework of centeredworlds, cannot model a special class of collective de se thoughts. A brief survey of this problem's solution space shows that collective de se thoughts pose a new challenge for modeling mental content. (shrink)
Counterfactual attitudes like imagining, dreaming, and wishing create a problem for the standard formal semantic theory of de re attitude ascriptions. I show how the problem can be avoided if we represent an agent's attitudinal possibilities using "multi-centeredworlds", possible worlds with multiple distinguished individuals, each of which represents an individual with whom the agent is acquainted. I then present a compositional semantics for de re ascriptions according to which singular terms are "assignment-sensitive" expressions and attitude verbs (...) are "assignment shifters". (shrink)
0. Relativistic Content In standard semantics, propositional content, whether it be the content of utterances or mental states, has a truth-value relative only to a possible world. For example, the content of my utterance of ‘Jim is sitting now’ is true just in case Jim is sitting at the time of utterance in the actual world, and the content of my belief that Alice will give a talk tomorrow is true just in case Alice will give a talk on the (...) day following the occurrence of my belief state in the actual world. Let us call propositional content which has a truth-value relative only to a possible world ‘non-relativistic content’. Non-relativistic content can be treated as either structured or unstructured. On the unstructured-content view, non-relativistic content is a set of possible worlds and bears the truth-value true just in case the actual world is a member of that set. For example, the content of my utterance of ‘Jim is working now’ at time t is the set of worlds in which Jim is working at t, and this content is true just in case the actual world is among those worlds. On the structured-content view, non-relativistic content is a set or conglomeration of properties and/or objects, where properties are features which objects possess regardless of who considers or observes them and regardless of when they are being considered or observed. Such properties are said to be (or represent) functions from possible worlds to extensions. Relative to a possible world they determine a set of objects instantiating the property. For example, relative to the actual world the property of being human determines the set of actual humans. Not all content is non-relativistic. Let us say that propositional content is relativistic just in case it possesses a truth-value only relative to a centered world. A centered world is a possible world in which an individual and a time are marked, where the marked individual.. (shrink)
When one considers one's own persistence over time from the first-person perspective, it seems as if facts about one's persistence are "further facts," over and above facts about physical and psychological continuity. But the idea that facts about one's persistence are further facts is objectionable on independent theoretical grounds: it conflicts with physicalism and requires us to posit hidden facts about our persistence. This essay shows how to resolve this conflict using the idea that imagining from the first-person point of (...) view is a guide to centered possibility , a type of possibility analyzed in terms of centeredworlds. CiteULike Connotea Del.icio.us Digg Reddit Technorati What's this? (shrink)
I argue that strong representationalism, the view that for a perceptual experience to have a certain phenomenal character just is for it to have a certain representational content (perhaps represented in the right sort of way), encounters two problems: the dual looks problem and the duplication problem. The dual looks problem is this: strong representationalism predicts that how things phenomenally look to the subject reflects the content of the experience. But some objects phenomenally look to both have and not have (...) certain properties, for example, my bracelet may phenomenally look to be circular-shaped and oval-shaped (and hence non-circularshaped). So, if strong representationalism is true, then the content of my experience ought to represent my bracelet as being both circular-shaped and non-circular-shaped. Yet, intuitively, the content of my experience does not represent my bracelet as being both circular-shaped and non-circular-shaped. The duplication problem is this. On a standard conception of content, spatio-temporally distinct experiences and experiences had by distinct subjects may differ in content despite the fact that they are phenomenally indistinguishable. But this undermines the thesis that phenomenal character determines content. I argue that the two problems can be solved by applying a version of an idea from David Chalmers, which is to recognize the existence of genuinely centered properties in the content of perceptual experience. (shrink)
This paper extends the framework of Lasersohn (2005) to give an updated semantic approach to control. On the view proposed here, all clausal constituents express (have as their semantic intensions) sets of centred worlds. In control constructions, the subject of the lower clause (‘PRO’) is identified with the ‘centre’ of a centred world. This view allows for a uniform semantic analysis of clauses, including those with and without null subjects, and for propositional attitude predicates.
I defend a general rule for updating beliefs that takes into account both the impact of new evidence and changes in the subject’s location. The rule combines standard conditioning with a shifting operation that moves the center of each doxastic possibility forward to the next point where information arrives. I show that well-known arguments for conditioning lead to this combination when centered information is taken into account. I also discuss how my proposal relates to other recent proposals, what results (...) it delivers for puzzles like the Sleeping Beauty problem, and whether there are diachronic constraints on rational belief at all. (shrink)
The essential premise of the human-centered technology paradigm was clearly formulated by Howard Rosenbrock in the 1970s: technology should enrich rather than impoverish people’s work and life conditions. The increasing influence of technology in modern societies has been seen by some as offering great promise for the future, but by others as creating the electronic surveillance and/or manipulation of human genes, minds and beliefs. This paper approaches technological worlds as cultural visions in order to discuss and reflect the (...) paradoxical process of viewing technology as part of a hope for a more sustainable and human-centered future as well as part of an apocalypse of surveillance, violence and catastrophes. (shrink)
The Property Theory of attitudes holds that the contents of mental states --- especially de se states --- are properties. The "nonexistence problem" for the Property Theory holds that the theory gives the wrong consequences as to which worlds "fit" which mental states: which worlds satisfy desires, make beliefs true, and so on. If I desire to not exist, since there is no world where I have the property of not existing, my desire is satisfied in no (...) class='Hi'>worlds. In this paper I argue that the problem can be solved with a suitable account of how properties as mental states fit worlds. The solution relies on a distinction between to kinds of property-instantiation at worlds inspired by Fine's distinction between "inner" and "outer" truth. (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.
Colors aren't as real as shapes. Shapes are full?fledged qualities of things in themselves, independent of how they're perceived and by whom. Colors aren't. Colors are merely qualities of things as they are for us, and the colors of things depend on who is perceiving them. When we take the fully objective view of the world, things keep their shapes, but the colors fall away, revealed as the mere artifacts of our own subjective, parochial perspective on the world that they (...) are. (shrink)
t f I hear the patter of little feet around the house, I expect Bruce. What I expect is a cat, a particular cat. If I heard such a patter in another house, I might expect a cat but no particular cat. What I expect then seems to be a Meinongian incomplete cat. I expect winter, expect stormy weather, expect to shovel snow, expect fatigue Ã¢â¬â a season, a phenomenon, an activity, a state. I expect that someday mankind will inhabit (...) at least five planets. This time what I expect is a state of affairs. If we let surface grammar be our guide, the objects of expectation seem quite a miscellany. The same goes for belief, since expectation is one kind of belief. The same goes for desire: I could want Bruce, want a cat but no particular cat, want winter, want stormy weather, want to shovel snow, want fatigue, or want that someday mankind will inhabit at least five planets. The same goes for other attitudes to the extent that they consist partly of beliefs or desires or lacks thereof. But the seeming diversity of objects might be an illusion. Perhaps the objects of attitudes are uniform in category, and it is our ways of speaking elliptically about these uniform objects that are diverse. That indeed is our consensus. We mostly think that the attitudes uniformly have propositions as their objects. That is why we speak habitually of "propositional attitudes.". (shrink)
It's a presupposition of a very common way of thinking about contextsensitivity in language that the semantic contribution made by a bit of context-sensitive vocabulary is sensitive only to features of the speaker's situation at the time of utterance. I argue that this is false, and that we need a theory of context-dependence that allows for content to depend not just on the features of the utterance's origin, but also on features of its destination. There are cases in which a (...) single utterance semantically conveys different propositions to different members of its audience, which force us to say that what a sentence conveys depends not just on the context in which it is uttered, but also on the context in which it is received. (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)
Relativism offers an ingenious way of accommodating most of our intuitions about 'know': the truth-value of sentences containing 'know' is a function of parameters determined by a context of use and a context of assessment. This sort of double-indexing provides a more adequate account of the linguistic data involving 'know' than does standard contextualism. However, relativism has come under recent attack: it supposedly cannot account for the factivity of 'know', and it entails, counterintuitively, that circumstances of evaluation have features that (...) cannot be shifted by any intensional operator. I offer replies to these objections on behalf of the relativist. I then argue that a version of contextualism can account for the same data as relativism without relativizing sentence truth to contexts of assessment. This version of contextualism is thus preferable to relativism on methodological grounds. (shrink)
I suggest a way of extending Stalnaker’s account of assertion to allow for centered content. In formulating his account, Stalnaker takes the content of assertion to be uncentered propositions: entities that are evaluated for truth at a possible world. I argue that the content of assertion is sometimes centered: the content is evaluated for truth at something within a possible world. I consider Andy Egan’s proposal for extending Stalnaker’s account to allow for assertions with centered content. I (...) argue that Egan’s account does not succeed. Instead, I propose an account on which the contents of assertion are identified with sets of multi-centeredworlds. I argue that such a view not only provides a plausible account of how assertions can have centered content, but also preserves Stalnaker’s original insight that successful assertion involves the reduction of shared possibilities. (shrink)
This paper argues for a possible worlds theory of the content of pictures, with three complications: depictive content is centred, two-dimensional and structured. The paper argues that this theory supports a strong analogy between depictive and other kinds of representation and the platitude that depiction is mediated by resemblance.
This paper argues that expected utility theory for actions in chancy environments should be formulated in terms of centered chances. The subjective expected utility of an option A may be seen as a weighted sum of the utilities of A in different possible worlds, with weights being the credences that the agent assigns to these worlds. The utility of A in a given world is then definable as a weighted sum of the values of A’s different possible (...) outcomes, with weights being the conditional chances (in that world) of these outcomes if A were performed. On the centered-chance view, the chances to be used as weights in the definition of utility are centered. Unlike ordinary chances, centered chances depend not only on what happens prior to the agent’s choice but also on the events that occur after the choice. Thus, to give an example, suppose that the action under consideration results in a bad outcome due to some event whose ordinary (i.e. non-centered) chance of occurring was very low at the time of choice. Then the utility of that action in the actual world could be high on the non-centered view, but on the centered view that utility is negative (as distinct from its expected utility), since the centered chance of the event in question given the action was one, given that it did actually take place. A precise definition of centered chances is not easy to frame, but the concept can be made intuitively clear. The resulting decision theory is, in my opinion, philosophically more satisfactory than the extant proposals, even though it doesn’t differ much in its practical recommendations, with the exception of some rather peculiar cases. (shrink)
Naturalistic thinking and knowing, the tacit, experiential, and intuitive reasoning of everyday interaction, have long been regarded as inferior to formal reason and labeled primitive, fallible, subjective, superstitious, and in some cases ineffable. But, naturalistic thinking is more rational and definable than it appears. It is also relevant to design. Inquiry into the mechanisms of naturalistic thinking and knowledge can bring its resources into focus and enable designers to create better, human-centered designs for use in real-world settings. This article (...) makes a case for the explicit, formal study of implicit, naturalistic thinking within the fields of design. It develops a framework for defining and studying naturalistic thinking and knowledge, for integrating them into design research and practice, and for developing a more integrated, consistent theory of knowledge in design. It will (a) outline historical definitions of knowledge, attitudes toward formal and naturalistic thinking, and the difficulties presented by the co-presence of formal and naturalistic thinking in design, (b) define and contrast formal and naturalistic thinking as two distinct human cognitive systems, (c) demonstrate the importance of naturalistic cognition in formal thinking and real-world judgment, (d) demonstrate methods for researching naturalistic thinking that can be of use in design, and (e) briefly discuss the impact on design theory of admitting naturalistic thinking as valid, systematic, and knowable. (shrink)
It has recently been proposed that the framework of semantic relativism be put to use to describe mental content, as deployed in some of the fundamental operations of the mind. This programme has inspired in particular a novel strategy of accounting for the essential egocentricity of first-personal or de se thoughts in relativist terms, with the advantage of dispensing with a notion of self-representation. This paper is a critical discussion of this strategy. While it is based on a plausible appeal (...) to cognitive economy, the relativist theory does not fully account for the epistemic profile that distinguishes de se thinking, as some of its proponents hope to do. A deeper worry concerns the reliance of the theory on a primitive notion of “centre” that hasn’t yet received enough critical attention, and is ambiguous between a thin and a rich reading. I argue that while the rich reading is required if the relativist analysis of the de se is to achieve its most ambitious aims, it also deprives the theory of much of its explanatory power. (shrink)
The standard view about counterfactuals is that a counterfactual (A > C) is true if and only if the A-worlds most similar to the actual world @ are C-worlds. I argue that the worlds conception of counterfactuals is wrong. I assume that counterfactuals have non-trivial truth-values under physical determinism. I show that the possible-worlds approach cannot explain many embeddings of the form (P > (Q > R)), which intuitively are perfectly assertable, and which must be true (...) if the contingent falsity of (Q > R) is to be explained. If (P > (Q > R)) has a backtracking reading then the contingent facts that (Q > R) needs to be true in the closest P-worlds are absent. If (P > (Q > R)) has a forwardtracking reading, then the laws required by (Q > R) to be true in the closest P-worlds will be absent, because they are violated in those worlds. Solutions like lossy laws or denial of embedding won't work. The only approach to counterfactuals that explains the embedding is a pragmatic metalinguistic approach in which the whole idea that counterfactuals are about a modal reality, be it abstract or concrete, is given up. (shrink)
David Lewis's book 'On the Plurality of Worlds' mounts an extended defense of the thesis of modal realism, that the world we inhabit the entire cosmos of which we are a part is but one of a vast plurality of worlds, or cosmoi, all causally and spatiotemporally isolated from one another. The purpose of this article is to provide an accessible summary of the main positions and arguments in Lewis's book.
In this paper, I investigate whether we can use a world-involving framework to model the epistemic states of non-ideal agents. The standard possible-world framework falters in this respect because of a commitment to logical omniscience. A familiar attempt to overcome this problem centers around the use of impossible worlds where the truths of logic can be false. As we shall see, if we admit impossible worlds where “anything goes” in modal space, it is easy to model extremely non-ideal (...) agents that are incapable of performing even the most elementary logical deductions. A much harder, and considerably less investigated challenge is to ensure that the resulting modal space can also be used to model moderately ideal agents that are not logically omniscient but nevertheless logically competent. Intuitively, while such agents may fail to rule out subtly impossible worlds that verify complex logical falsehoods, they are nevertheless able to rule out blatantly impossible worlds that verify obvious logical falsehoods. To model moderately ideal agents, I argue, the job is to construct a modal space that contains only possible and non-trivially impossible worlds where it is not the case that “anything goes”. But I prove that it is impossible to develop an impossible-world framework that can do this job and that satisfies certain standard conditions. Effectively, I show that attempts to model moderately ideal agents in a world-involving framework collapse to modeling either logical omniscient agents, or extremely non-ideal agents. (shrink)
You and I can differ in what we say, or believe, even though the things we say, or believe, are logically equivalent. Discussing what is said, or believed, requires notions of content which are finer-grained than sets of (metaphysically or logically) possible worlds. In this paper, I develop the approach to fine-grained content in terms of a space of possible and impossible worlds. I give a method for constructing ersatz worlds based on theory of substantial facts. I (...) show how this theory overcomes an objection to actualist constructions of ersatz worlds and argue that it naturally gives rise to useful notions of fine-grained content. (shrink)
It is shown that the superposed wave function of a measuring device, in each branch of which there is a definite measurement result, does not correspond to many mutually unobservable but equally real worlds, as the superposed wave function can be observed in our world by protective measurement.
According to David Lewis, a realist about possible worlds must hold that actuality is relative: the worlds are ontologically all on a par; the actual and the merely possible differ, not absolutely, but in how they relate to us. Call this 'Lewisian realism'. The alternative, 'Leibnizian realism', holds that actuality is an absolute property that marks a distinction in ontological status. Lewis presents two arguments against Leibnizian realism. First, he argues that the Leibnizian realist cannot account for the (...) contingency of actuality. Second, he argues that the Leibnizian realist cannot explain why skepticism about one's own actuality is absurd. In this paper, I mount a defense of Leibnizian realism. (shrink)
Impossible worlds are representations of impossible things and impossible happenings. They earn their keep in a semantic or metaphysical theory if they do the right theoretical work for us. As it happens, a worlds-based account provides the best philosophical story about semantic content, knowledge and belief states, cognitive significance and cognitive information, and informative deductive reasoning. A worlds-based story may also provide the best semantics for counterfactuals. But to function well, all these accounts need use of impossible (...) and as well as possible worlds. So what are impossible worlds? Graham Priest claims that any of the usual stories about possible worlds can be told about impossible worlds, too. But far from it. I'll argue that impossible worlds cannot be genuine worlds, of the kind proposed by Lewis, McDaniel or Yagisawa. Nor can they be ersatz worlds on the model proposed by Melia or Sider. Constructing impossible worlds, it turns out, requires novel metaphysical resources. (shrink)
According to an attractive account of belief, our beliefs have centered content. According to an attractive account of communication, we utter sentences to express our beliefs and share them with each other. However, the two accounts are in conflict. We have to either change our understanding of belief or modify our theory of communication. In this paper, I explore the consequences of holding on to the claim that beliefs have centered content. If we do in fact express the (...)centered content of our beliefs, the content of the belief the hearer acquires cannot in general be identical to the content the speaker expresses. I sketch an alternative account of communication, the Recentering model, that accepts this consequence and explains how the expressed and the acquired content are related. (shrink)
Theories of content are at the centre of philosophical semantics. The most successful general theory of content takes contents to be sets of possible worlds. But such contents are very coarse-grained, for they cannot distinguish between logically equivalent contents. They draw intensional but not hyperintensional distinctions. This is often remedied by including impossible as well as possible worlds in the theory of content. Yet it is often claimed that impossible worlds are metaphysically obscure; and it is sometimes (...) claimed that their use results in a trivial theory of content. In this paper, I set out the need for impossible worlds in a theory of content; I briefly sketch a metaphysical account of their nature; I argue that worlds in general must be very fine-grained entities; and, finally, I argue that the resulting conception of impossible worlds is not a trivial one. (shrink)
In Everett's many worlds interpretation, quantum measurements are considered to be decoherence events. If so, then inexact decoherence may allow large worlds to mangle the memory of observers in small worlds, creating a cutoff in observable world size. Smaller world are mangled and so not observed. If this cutoff is much closer to the median measure size than to the median world size, the distribution of outcomes seen in unmangled worlds follows the Born rule. Thus deviations (...) from exact decoherence can allow the Born rule to be derived via world counting, with a finite number of worlds and no new fundamental physics. (shrink)
Among the most remarkable developments in metaphysics since the 1950’s is the explosion of philosophical interest in possible worlds. This paper proposes an explanation of what possible worlds are, and argues that this proposal, the interpreted models conception, should be attractive to anyone who thinks that modal facts are primitive, and so not to be explained in terms of some non-modal notion of “possible world.” I articulate three constraints on any acceptable primitivist explanation of the nature of possible (...)worlds, and show that the interpreted models conception meets the three constraints. (shrink)
Everett (1957a, b, 1973) relative-state formulation of quantum mechanics has often been taken to involve a metaphysical commitment to the existence of many splitting worlds each containing physical copies of observers and the objects they observe. While there was earlier talk of splitting worlds in connection with Everett, this is largely due to DeWitt’s (Phys Today 23:30–35, 1970) popular presentation of the theory. While the thought of splitting worlds or parallel universes has captured the popular imagination, Everett (...) himself favored the language of elements, branches, or relative states in describing his theory. The result is that there is no mention of splitting worlds or parallel universes in any of Everett’s published work. Everett, however, did write of splitting observers and was willing to adopt the language of many worlds in conversation with people who were themselves using such language. While there is evidence that Everett was not entirely comfortable with talk of many worlds, it does not seem to have mattered much to him what language one used to describe pure wave mechanics. This was in part a result of Everett’s empirical understanding of the cognitive status of his theory. (shrink)
How do ordinary objects persist through time and across possible worlds ? How do they manage to have their temporal and modal properties ? These are the questions adressed in this book which is a "guided tour of theories of persistence". The book is divided in two parts. In the first, the two traditional accounts of persistence through time (endurantism and perdurantism) are combined with presentism and eternalism to yield four different views, and their variants. The resulting views are (...) then examined in turn, in order to see which combinations are appealing and which are not. It is argued that the 'worm view' variant of eternalist perdurantism is superior to the other alternatives. In the second part of the book, the same strategy is applied to the combinations of views about persistence across possible worlds (trans-world identity, counterpart theory, modal perdurants) and views about the nature of worlds, mainly modal realism and abstractionism. Not only all the traditional and well-known views, but also some more original ones, are examined and their pros and cons are carefully weighted. Here again, it is argued that perdurance seems to be the best strategy available. (shrink)
The most commonly heard proposals for reducing possible worlds to language succumb to a simple cardinality argument: it can be shown that there are more possible worlds than there are linguistic entities provided by the proposal. In this paper, I show how the standard proposals can be generalized in a natural way so as to make better use of the resources available to them, and thereby circumvent the cardinality argument. Once it is seen just what the limitations are (...) on these more general proposals, it can be clearly seen where the real difficulty lies with any attempt to reduce possible worlds to language. Roughly, the difficulty is this: no actual language could have the descriptive resources needed to represent all the ways things might have been. I conclude by arguing that this same difficulty spells doom for any nominalist or conceptualist proposal for reducing possible worlds. (shrink)
Lewisian Genuine Realism (GR) about possible worlds is often deemed unable to accommodate impossible worlds and reap the benefits that these bestow to rival theories. This thesis explores two alternative extensions of GR into the terrain of impossible worlds. It is divided in six chapters. Chapter I outlines Lewis’ theory, the motivations for impossible worlds, and the central problem that such worlds present for GR: How can GR even understand the notion of an impossible world, (...) given Lewis’ reductive theoretical framework? Since the desideratum is to incorporate impossible worlds into GR without compromising Lewis’ reductive analysis of modality, Chapter II defends that analysis against (old and new) objections. The rest of the thesis is devoted to incorporating impossible worlds into GR. Chapter III explores GR-friendly impossible worlds in the form of set-theoretic constructions out of genuine possibilia. Then, Chapters IV-VI venture into concrete impossible worlds. Chapter IV addresses Lewis’ objection against such worlds, to the effect that contradictions true at impossible worlds amount to true contradictions tout court. I argue that even if so, the relevant contradictions are only ever about the non-actual, and that Lewis’ argument relies on a premise that cannot be nonquestion- beggingly upheld in the face of genuine impossible worlds in any case. Chapter V proposes that Lewis’ reductive analysis can be preserved, even in the face of genuine impossibilia, if we differentiate the impossible from the possible by means of accessibility relations, understood non-modally in terms of similarity. Finally, Chapter VI counters objections to the effect that there are certain impossibilities, formulated in Lewis’ theoretical language, which genuine impossibilia should, but cannot, represent. I conclude that Genuine Realism is still very much in the running when the discussion turns to impossible worlds. (shrink)
There are many parallels between the role of possible worlds in modal logic and that of times in tense logic. But the similarities only go so far, and it is important to note where the two come apart. This paper argues that even though worlds and times play similar roles in the model theories of modal and tense logic, there is no tense analogue of the possible-worlds analysis of modal operators. An important corollary of this result is (...) that presentism cannot be the tense analogue of actualism. (shrink)
Modal realism -- Time, space, world -- Existence -- Actuality -- Modal realism and modal tense -- Transworld individuals and their identity -- Existensionalism -- Impossibility -- Proposition and relief -- Fictional worlds -- Epistemology.
If realism about possible worlds is to succeed in eliminating primitive modality, it must provide an 'analysis' of possible world: nonmodal criteria for demarcating one world from another. This David Lewis has done. Lewis holds, roughly, that worlds are maximal unified regions of logical space. So far, so good. But what Lewis means by 'unification' is too narrow, I think, in two different ways. First, for Lewis, all worlds are (almost) 'globally' unified: at any world, (almost) every (...) part is directly linked to (almost) every other part. I hold instead that some worlds are 'locally' unified: at some worlds, parts are directly linked only to "neighboring" parts. Second, for Lewis, each world is (analogically) 'spatio-temporally' unified; every world is 'spatio-temporally' isolated from every other. I hold instead: a world may be unified by nonspatio-temporal relations; every world is 'absolutely' isolated from every other. If I am right, Lewis's conception of logical space is impoverished: perfectly respectable worlds are missing. (shrink)
This paper reports on an ongoing ARC Discovery Project that is conducting design research into learning in collaborative virtual worlds (CVW).The paper will describe three design components of the project: (a) pedagogical design, (b)technical and graphics design, and (c) learning research design. The perspectives of each design team will be discussed and how the three teams worked together to produce the CVW. The development of productive failure learning activities for the CVW will be discussed and there will be an (...) interactive demonstration of the project's CVW. (shrink)
I outline a neo-Fregean strategy in the debate on the existence of possible worlds. The criterion of identity and the criterion of application are formulated. Special attention is paid to the fact that speakers do not possess proper names for worlds. A broadly Quinean solution is proposed in response to this difficulty.
In the future, human destiny may depend on our ethics. In particular, biotechnology and expansion in space can transform life, raising profound questions. Guidance may be found in Life-centered ethics, as biotic ethics that value the basic patterns of organic gene/protein life, and as panbiotic ethics that always seek to expand life. These life-centered principles can be based on scientific insights into the unique place of life in nature, and the biological unity of all life. Belonging to life (...) then implies a human purpose: to safeguard and propagate life. Expansion in space will advance this purpose but will also raise basic questions. Should we expand all life or only intelligent life? Should we aim to create populations of trillions? Should we seed other solar systems? How far can we change but still preserve the human species, and life itself? The future of all life may be in our hands, and it can depend on our guiding ethics whether life will fulfil its full potentials. Given such profound powers, life-centered ethics can best secure future generations. Our descendants may then understand nature more deeply, and seek to extend life indefinitely. In that future, our human existence can find a cosmic purpose. (shrink)
We show that, given standard assumptions about classical dynamical systems, Lewis' conception of possible worlds is incompatible with classical physics in that it would imply that all dynamical systems were integrable.