Philosophers of quantum mechanics have generally addressed exceedingly simple systems. Laura Ruetsche offers a much-needed study of the interpretation of more complicated systems, and an underexplored family of physical theories, such as quantum field theory and quantum statistical mechanics, showing why they repay philosophical attention. She guides those familiar with the philosophy of ordinary QM into the philosophy of 'QM infinity', by presenting accessible introductions to relevant technical notions and the foundational questions they frame--and then develops and defends answers to (...) some of those questions. Finally, Ruetsche highlights ties between the foundational investigation of QM infinity and philosophy more broadly construed, in particular by using the interpretive problems discussed to motivate new ways to think about the nature of physical possibility and the problem of scientific realism. (shrink)

Stephen Hawking has argued that universes containing evaporating black holes can evolve from pure initial states to mixed final ones. Such evolution is non-unitary and so contravenes fundamental quantum principles on which Hawking's analysis was based. It disables the retrodiction of the universe's initial state from its final one, and portends the time-asymmetry of quantum gravity. Small wonder that Hawking's paradox has met with considerable resistance. Here we use a simple result for C*-algebras to offer an argument for pure-to-mixed state (...) evolution in black hole evaporation, and review responses to the Hawking paradox with respect to how effectively they rebut this argument. (shrink)

Wiederkehr des Raumes?. Topologisches Paradigmen ; Rückkehr zum gelebten Raum ; Raumkonzepte und Raumpraktiken ; Regionale oder fundamentale Räumlichkeit ; Zweideutigkeiten und Paradoxien der Lebenswelt -- Polarität von Ort und Raum. Phänomenologische Topik ; Wo-Frage im Schatten der Was-Frage ; Ortsbestimmung als Antwort auf eine Wo-Frage ; Fremde und eigene Wo-Frage ; Hier als Standort : Grund und Boden ; Woher und Wohin : Wegstrecken ; Worin : offene und geschlossene Räume ; Ringsum : Umgebung, Umwelt und Welt ; Wie (...) weit : Vermessene Räume -- Leibliches Wohnen im Raum. Vielfalt des Raumes ; Verankerung im Hier ; Raumachsen ; Durchmessung, Dehnung und Schrumpfung des Raumes ; Nähe und Ferne ; Drinnen und Draußen ; Interieur und Exterieur im Blickfield der Malerei ; Raumanlage und Raumbühne ; Raumtechniken und Ortskarten ; Lokale Räume und globaler Raum -- Ortsverschiebungen. Hier und Anderswo ; Aktualität, Habitualität und Virtualität der räumlichen Bewegung ; Spuren der Zeit im Raum ; Zersprengter Raum ; Telepräsenz ; Fremdorte und andere Räume ; Gemeinorte und globaler Raum ; Gastlichkeit ; Coda : Topos : Atopie : Heterotopien -- Zeitverdoppelung und Zeitverschiebung. Zwischen Mythos und Logos ; Frage nach der Zeit ; Zeitverdoppelung in der Rede und Zeitverkörperung ; Zeitverschiebung zwischen Pathos und Respons ; Zeitverschiebung und Reaktionszeit ; Der entrückte Anfang im Roman und auf der Bühne ; Zeit der Sinne ; Jenseits von Erinnerung und Erwartung ; Rhythmen und Tempi ; Zwischen Leere und Erfüllung ; Coda : Anderswo enden -- Die verändernde Kraft der Wiederholung. Wiederholungsexperiment ; Sich wiederholdende Erfahrung ; Widerholung als Rettung aus der Zeit ; Altes und Neues im Widerstreit ; Unwiederholbares in der Zeit -- Die Wahrscheinlichkeit von Zukünftigem im Anschluß an Aristoteles. Handlungsperspektive ; Die drohende Seeschlacht ; Wahrscheinlichkeit und Häufigkeit ; Zwischen Gewißheit und Ungewißheit ; Rückzug auf pratische Gewißheit ; Zwischen Entwurf und Erwartung ; Unwahrscheinliche Zukunft -- Kommen und Gehen in der Zeit im Anschluß an Merleau-Ponty. Frühe dialektik der Zeit ; Zeit als bloßes Nacheinander ; Totalität der Zeit : Präsenzfeld ; Riß der Zeit : Selbstaffektion ; Bewegung der Zeit : Vor- und Rückläufigkeit ; Wahrnehmung zwischen Vor- und Rückblick ; Handeln zwischen Vorsatz und Vorschlag ; Kommen und Gehen ; Chiasmus der Zeit -- Epilog : Verquickung von Ort, Raum und Zeit. (shrink)

This chapter covers the traditional role of responsibility, and the possible connections between response and responsibility. These connections are explored through the advance of trust and the surplus of the extraordinary in relation to the Third Party. The idea of responsibility comes from the sphere of juridical law, and has a theological touch. The classical conception presented suffers from a permanent erosion that is reinforced by systemic constraints. Trust is a natural element of every community that is together applied by (...) common aims in life. The phenomenon of trust refers to the bond, the nexus, which holds together the members of a community, creating the requisite solidarity. The term ‘trust’ or ‘confidence’ should not primarily read as a substantive, but as a verb or as the derivative of a verb. Furthermore, it is noted that the responsive ethics proposed could function as a permanent corrective. (shrink)

A number of arguments have been given to show that the modal interpretation of ordinary nonrelativistic quantum mechanics cannot be consistently extended to the relativistic setting. We find these arguments inconclusive. However, there is a prima facie reason to think that a tension exists between the modal interpretation and relativistic invariance; namely, the best candidate for a modal interpretation adapted to relativistic quantum field theory, a prescription due to Rob Clifton, comes out trivial when applied to a number of systems (...) of physical interest. However, it is far from clear whether this difficulty for the modal interpretation is traceable to relativistic invariance per se or to the infinite number of degrees of freedom involved. In any case, the proponents of the modal interpretation have work to do. (shrink)

Without directly addressing the Demarcation Problem for logic—the problem of distinguishing logical vocabulary from others—we focus on distinctive aspects of logical vocabulary in pursuit of a second goal in the philosophy of logic, namely, proposing criteria for the justification of logical rules. Our preferred approach has three components. Two of these are effectively Belnap’s, but with a twist. We agree with Belnap’s response to Prior’s challenge to inferentialist characterisations of the meanings of logical constants. Belnap argued that for a logical (...) constant to exist, its rules must be conservative over a previously given consequence relation and guarantee the uniqueness of the constant. The twist is that we require logical vocabulary to be provably conservative, not over a previously given formal consequence relation, but over a previously given meaningful vocabulary of a language. Uniqueness is also a feature defined in terms of provability: if two syntactically distinguished expressions are governed by the same rules, then formulas with them as main operators are interderivable. Belnap’s criteria are not only those for the existence of a logical constant, but more: they are what distinguishes logical vocabulary from all other expressions. It is the defining mark of a logical constant that it is provably conservative over the fragment of the language which excludes it and that its rules guarantee its uniqueness. The third component is the topic neutrality of logic. The provable conservativeness of logic over a previously given vocabulary of a language is motivated, in part, by appeal to molecularism in the theory of meaning. Molecularity is a feature endorsed by the theory of meaning as a whole, so it does not distinguish logical constants from other expressions. The same is true for conservativeness. We argue that molecularity, and hence conservativeness, are implicit presuppositions of speakers’ use of language: the addition of new vocabulary to a language is presupposed to be conservative. But this presupposition is one that we should be able reflectively to endorse (such as when attempting a rational reconstruction of the use of the vocabulary). Thus, where conservativeness is found to fail, this defect should be remedied and the use of the vocabulary corrected (as in classical negation) or excised altogether (as in pejoratives). We go on to characterise a notion of topic neutrality, which we argue applies to logical vocabulary. We then note that reflective endorsement of the conservativeness of a topic neutral vocabulary requires a proof that the vocabulary is conservative relative to any base vocabulary. Thus we require that logical vocabulary be demonstrably conservative. Allying this requirement, distinctive of logic, to a general consideration about the commitments of assertion yields a mode of justification for logical constants akin to some conceptions of Harmony, i.e., to the idea that the consequences of assertion of a logical complex need to be warranted by the grounds and ought to be the strongest consequences warranted by the grounds. Intuitionistic logic acquires a somewhat familiar justification but emanating from a new motivation. (shrink)

Good’s theorem is the apparent platitude that it is always rational to ‘look before you leap’: to gather information before making a decision when doing so is free. We argue that Good’s theorem is not platitudinous and may be false. And we argue that the correct advice is rather to ‘make your act depend on the answer to a question’. Looking before you leap is rational when, but only when, it is a way to do this.

One realist response to the pessimistic meta-induction distinguishes idle theoretical wheels from aspects of successful theories we can expect to persist and espouses realism about the latter. Implementing the response requires a strategy for identifying the distinguished aspects. The strategy I will call renormalization group realism has the virtue of directly engaging the gears of our best current physics—perturbative quantum field theories. I argue that the strategy, rather than disarming the skeptical possibilities evinced by the pessimistic meta-induction, forces them to (...) retreat a level. I also suggest that those skeptical possibilities continue to carry force. (shrink)

Epistemologists have recently noted a tension between (i) denying access internalism, and (ii) maintaining that rational agents cannot be epistemically akratic, believing claims akin to ‘p, but I shouldn’t believe p’. I bring out the tension, and develop a new way to resolve it. The basic strategy is to say that access internalism is false, but that counterexamples to it are ‘elusive’ in a way that prevents rational agents from suspecting that they themselves are counterexamples to the internalist principles. I (...) argue that this allows us to do justice to the motivations behind both (i) and (ii). And I explain in some detail what a view of evidence that implements this strategy, and makes it independently plausible, might look like. (shrink)

The availability of unitarily inequivalent representations of the canonical commutation relations constituting a quantization of a classical field theory raises questions about how to formulate and pursue quantum field theory. In a minimally technical way, I explain how these questions arise and how advocates of the Hilbert space and of the algebraic approaches to quantum theory might answer them. Where these answers differ, I sketch considerations for and against each approach, as well as considerations which might temper their apparent rivalry.

Taking Arthur Fine’s The Shaky Game as my inspiration, and the recent 25th anniversary of the publication of that work as the occasion to exercise that inspiration, I sketch an alternative to the “Naturalism” prevalent among philosophers of physics. Naturalism is a methodology eventuating in a metaphysics. The methodology is to seek the deep framework assumptions that make the best sense of science; the metaphysics is furnished by those assumptions and supported by their own support of science. The alternative presented (...) here, which I call “Locavoracity,” shares Naturalism’s commitment to making sense of science, but alters Naturalism’s methodology. The Locavore’s sense-making projects are piecemeal, rather than sweeping. The Locavore’s hypothesis is that the collection of local sense-making projects fails to issue a single overarching unifying framework deserving of the title “the metaphysics that makes the best sense of science.” I muster some examples supporting the Locavore hypothesis from the interpretation of quantum field theories. (shrink)

If a classical system has infinitely many degrees of freedom, its Hamiltonian quantization need not be unique up to unitary equivalence. I sketch different approaches (Hilbert space and algebraic) to understanding the content of quantum theories in light of this non‐uniqueness, and suggest that neither approach suffices to support explanatory aspirations encountered in the thermodynamic limit of quantum statistical mechanics.

This comment deals with some basic elements Searle uses in order to construct social reality, i.e. togetherness, we-intentionality and the distinction between institutional and brute facts. The commentator argues that Searle’s theory tends to a partial biologism because lacking a sufficient concept of embodiment. Consequently ‘pre-institutional facts’ such as eating, copulating, working or torturing are systematically underdetermined. On the deontic level the theory relies on natural processes of conventional power. So the distinction between factual acceptance and acceptability is blurred by (...) a sort of conformism, and one neglects the status of dissidents and victims whose belonging to the predominant ‘we’ remains highly dubious. (shrink)

Starting from the standard quantum formalism for a single spin 1/2 system (e.g., an electron), this essay develops a model rich enough not only to afford an explication of symmetry breaking but also to frame questions about how to circumscribe physical possibility on behalf of theories that countenance symmetry breaking.

We discuss the intertwined topics of Fulling non‐uniqueness and the Unruh effect. The Fulling quantization, which is in some sense the natural one for an observer uniformly accelerated through Minkowski spacetime to adopt, is often heralded as a quantization of the Klein‐Gordon field which is both physically relevant and unitarily inequivalent to the standard Minkowski quantization. We argue that the Fulling and Minkowski quantizations do not constitute a satisfactory example of physically relevant, unitarily inequivalent quantizations, and indicate what it would (...) take to settle the open question of whether a satisfactory example exists. A popular gloss on the Unruh effect has it that an observer uniformly accelerated through the Minkowski vacuum experiences a thermal flux of Rindler quanta. Taking the Unruh effect, so glossed, to establish that the notion of particle must be relativized to a reference frame, some would use it to demote the particle concept from fundamental status. We explain why technical results do not support the popular gloss and why the attempted demotion of the particle concept is both unsuccessful and unnecessary. Fulling non‐uniqueness and the Unruh effect merit attention despite these negative verdicts because they provide excellent vehicles for illustrating key concepts of quantum field theory and for probing foundational issues of considerable philosophical interest. (shrink)

When Sandra Harding called for an epistemology of science whose systematic attention to the gendered Status of epistemic agents renders it ‘less partial and distorted’ than ‘traditional’ epistemologies, some commentators recoiled in horror. Propelled by ‘a mad form of the genetic fallacy’ they said, she descends ‘the slide to an arational account of science.’ On a less melodramatic reading, feminist epistemologies such as Harding's advocate not irrationalism, but senses of rationality more expanded than those which they associate with ‘traditional’ epistemology.

Bernhard Nickel presents a theory of generic sentences and the kind-directed modes of thought they express. The theory closely integrates compositional semantics with metaphysics to solve the problem that generics pose: what do generics mean? Generic sentences are extremely simple, yet if there are patterns to be discerned in terms of which are true and which are false, these patterns are subtle and complex. Ravens are black, and lions have manes: statistical measures cannot do justice to the facts, but (...) what else is there that has a hope of giving us insight into what we are capturing across so many domains? Nickel argues that generics are the top of a fundamentally explanatory iceberg, and that this explanatory framework is deeply intertwined with the semantics of the language we use to express them. In providing an integrated semantic and metaphysical theory of generics, he aims to solve old puzzles and draw attention to new phenomena. (shrink)

The simplest case of quantum field theory on curved spacetime—that of the Klein–Gordon field on a globally hyperbolic spacetime—reveals a dilemma: In generic circumstances, either there is no dynamics for this quantum field, or else there is a dynamics that is not unitarily implementable. We do not try to resolve the dilemma here, but endeavour to spell out the consequences of seizing one or the other horn of the dilemma.

In der vorliegenden Schrift soll Martin Buber als dem scharfen Diagnostiker unserer Zeit und dem Künder ewiger Wahrheiten die ganze Aufmerksamkeit gelten. Kein Denken lässt sich so wenig in billigen Schlagwörtern einfangen, wie das Martin Bubers. Die erste Aufgabe wird sein, die Situation in der wir leben, und die Buber meint, etwas näher zu bestimmen. Dies wird uns in die Lage setzen, jene Fragen zu vernehmen, die die Situation zu uns allen spricht. Sodann werden wir uns der besonderen Gestalt der (...) Buberschen Antwort zuwenden. Erst dann erscheint die Frage nach Herkunft und Inhalt der Antwort sinnvoll. In einem letzten Teil sollen dann gleichsam drei Bewährungsproben von Bubers Denken erörtert werden. (shrink)

We discuss the intertwined topics of Fulling non-uniqueness and the Unruh effect. The Fulling quantization, which is in some sense the natural one for an observer uniformly accelerated through Minkowski spacetime to adopt, is often heralded as a quantization of the Klein-Gordon field which is both physically relevant and unitarily inequivalent to the standard Minkowski quantization. We argue that the Fulling and Minkowski quantizations do not constitute a satisfactory example of physically relevant, unitarily inequivalent quantizations, and indicate what it would (...) take to settle the open question of whether a satisfactory example exists. A popular gloss on the Unruh effect has it that an observer uniformly accelerated through the Minkowski vacuum experiences a thermal flux of Rindler quanta. Taking the Unruh effect, so glossed, to establish that the notion of particle must be relativized to a reference frame, some would use it to demote the particle concept from fundamental status. We explain why technical results do not support the popular gloss and why the attempted demotion of the particle concept is both unsuccessful and unnecessary. Fulling non-uniqueness and the Unruh effect merit attention despite these negative verdicts because they provide excellent vehicles for illustrating key concepts of quantum field theory and for probing foundational issues of considerable philosophical interest. (shrink)

A normal state on a von Neumann algebra defines a countably additive probability measure over its projection lattice. The von Neumann algebras familiar from ordinary QM are algebras of all the bounded operators on a Hilbert space H, aka Type I factor von Neumann algebras. Their normal states are density operator states, and can be pure or mixed. In QFT and the thermodynamic limit of QSM, von Neumann algebras of more exotic types abound. Type III von Neumann algebras, for instance, (...) have no pure normal states; the pure states they do have fail to be countably additive. I will catalog a number of temptations to accord physical significance to non-normal states, and then give some reasons to resist these temptations: pure though they may be, non-normal states on non-Type I factor von Neumann algebras can't do the interpretive work we've come to expect from pure states on Type I factors; our best accounts of state preparation don't work for the preparation of non-normal states; there is a sense in which non-normal states fail to instantiate the laws of quantum mechanics. (shrink)