The Greenberger-Horne-Zeilinger state is the most famous example of a state with multiparticle entanglement. In this article we describe a group theoretic framework we have been developing for understanding the entanglement in general states of two or more quantum particles. As far as entanglement is concerned, two states of n spin-1/2 particles are equivalent if they are on the same orbit of the group of local rotations (U(2)n). We consider both pure and mixed states and calculate the number of independent (...) parameters needed to describe such states up to this equivalence. We describe how the entanglement of states in a given equivalence class may be characterized by the stability group of the action of the group of local rotations on any of the states in the class. We also show how to calculate invariants under the group of local actions for both pure and mixed states. In the case of mixed states we are able to explicitly exhibit sets of invariants which allow one to determine whether two generic mixed states are equivalent up to local unitary transformations. (shrink)

Frauchiger and Renner have recently claimed to prove that “Single-world interpretations of quantum theory cannot be self-consistent”. This is contradicted by a construction due to Bell, inspired by Bohmian mechanics, which shows that any quantum system can be modelled in such a way that there is only one “world” at any time, but the predictions of quantum theory are reproduced. This Bell–Bohmian theory is applied to the experiment proposed by Frauchiger and Renner, and their argument is critically examined. It is (...) concluded that it is their version of “standard quantum theory”, incorporating state vector collapse upon measurement, that is not self-consistent. (shrink)

According to quantum mechanics, statements about the future made by sentient beings like us are, in general, neither true nor false; they must satisfy a many-valued logic. I propose that the truth value of such a statement should be identified with the probability that the event it describes will occur. After reviewing the history of related ideas in logic, I argue that it gives an understanding of probability which is particularly satisfactory for use in quantum mechanics. I construct a lattice (...) of future-tense propositions, with truth values in the interval [0, 1], and derive logical properties of these truth values given by the usual quantum-mechanical formula for the probability of a history. (shrink)

It is argued that the conventional formulation of quantum mechanics is inadequate: the usual interpretation of the mathematical formalism in terms of the results of measurements cannot be applied to situations in which discontinuous transitions (''quantum jumps'') are observed as they happen, since nothing that can be called a measurement happens at the moment of observation. Attempts to force such observations into the standard mould lead to absurd results: ''a watched pot never boils''. Experiments show both that this result is (...) correct when the experiment does indeed consist of a series of measurements, and that it is not when the experiment consists of a period of observation: quantum jumps do happen. The possibilities for improving the formulation by incorporating transitions in the basic postulates are reviewed, and a satisfactory postulate is obtained by modifying a suggestion of Bell's. This requires a distinction between the external description of the whole of a physical system and internal descriptions which are themselves physical events in the system. It is shown that this gives correct results for simple unstable systems and for the quantum-jump experiments. (shrink)

The quantum-mechanical description of the world, including human observers, makes substantial use of entanglement. In order to understand this, we need to adopt concepts of truth, probability and time which are unfamiliar in modern scientific thought. There are two kinds of statements about the world: those made from inside the world, and those from outside. The conflict between contradictory statements which both appear to be true can be resolved by recognising that they are made in different perspectives. Probability, in an (...) objective sense, belongs in the internal perspective, and to statements in the future tense. Such statements obey a many-valued logic, in which the truth values are identified as probabilities. (shrink)

I discuss the meaning of probability in the Everett-Wheeler interpretation of quantum mechanics, together with the problem of defining histories. To resolve these, I propose an understanding of probability arising from a form of temporal logic: the probability of a future-tense proposition is identified with its truth value in a many-valued and context-dependent logic. In short, probability is degree of truth. These ideas appear to be new, but they are natural and intuitive, and relate to traditional naive ideas of time (...) and chance. Indeed, I argue that Everettian quantum mechanics is the only form of scientific theory that truly incorporates the perception that the future is open. (shrink)

We examine the possible states of subsystems of a system of bits or qubits. In the classical case (bits), this means the possible marginal distributions of a probability distribution on a finite number of binary variables; we give necessary and sufficient conditions for a set of probability distributions on all proper subsets of the variables to be the marginals of a single distribution on the full set. In the quantum case (qubits), we consider mixed states of subsets of a set (...) of qubits; in the case of three qubits we find quantum Bell inequalities—necessary conditions for a set of two-qubit states to be the reduced states of a mixed state of three qubits. We conjecture that these conditions are also sufficient. (shrink)

There are two broad opposing classes of attitudes to reality with corresponding attitudes to knowledge. I argue that these attitudes can be compatible, and that quantum theory requires us to adopt both of them.

In lieu of an abstract, here is a brief excerpt of the content:A Bridge From Analysis to Action:Psychodynamic Analyses of Religion and Michael S. Hogue's American ImmanenceAJ Turner (bio)I. IntroductionThe purpose of this essay is to work constructively with Michael S. Hogue's groundbreaking American Immanence: Democracy for an Uncertain World to demonstrate how psychodynamic analyses of religion are essential theoretical allies in the fight for resilient democracy. The "revolution in mind"1 that psychodynamic approaches contribute, especially in their analyses of religion, (...) both complements and complicates socio-political theory as a whole. In the improvisational spirit of "yes-and," the goal here is not to identify and decry the failures and shortcomings of Hogue's theopolitical vision but rather to inspire the recovery of a sibling discourse—a kind of "rebirth of a forgotten alternative"2—that also draws deeply from the American immanental tradition in order to add psychodynamic depth to Hogue's timely and important analysis. Psychodynamic theories of religion shed light on how symbolic identifications, including and especially ultimate concerns, structure personal and collective experience. By engaging religion and theology sympathetically, constructively, and creatively, theorists such as Rollo May, Gordon Allport, Karen Horney, Erich Fromm, and Ernest Becker departed from the skepticism, reductionism, and dismissal that characterized psychoanalytic analyses of religion in the wake of Freud.3 Each of these figures, and especially Becker whose work will be a focus in this essay, are noteworthy interlocutors for extending Hogue's theopolitical theorizing of resilient democracy, particularly in how they drew unique inspiration from the American immanental tradition [End Page 44] in their social analyses. In this respect, they provide a more robust theorization of the psychosocial conditions of the associational ethos needed to connect Hogue's conception of resilient democracy with forms of agonistic organization and democratic activism. Briefly stated, psychodynamic approaches are a helpful bridge for connecting these proposals to strategies of organization, their impediments, and collective action.In this way, both psychodynamic analyses of religion and Hogue's theopolitical innovation insist that no revolutionary political change is possible, and certainly not of the kind or scale needed to counter our wickedly entangled global crises, without a deep engagement with theological imaginaries. They differ, however, in their theoretical aims. Whereas Hogue compellingly argues for the political upshot of a theology deriving from the American immanental tradition, psychodynamic analysts of religion focus on the function of ultimate concerns in individual and collective life. In other words, American Immanence rests on a methodology of analyzing the philosophical and theological assumptions that have contributed to our climate crises and then presenting clear and compelling articulation of an alternative paradigm meant to open up new ways of being. In contrast psychodynamic analyses leverage conceptual clarity of psychic reality for the fundamentally therapeutic aim of transformation. At their best, both approaches share what could be called an etiological orientation to ontological questions in order to provide liberative alternatives through rational understanding and clarification, but the terrain, and thus the problems they hope to mitigate in their analyses are focused differently. Extending the visual metaphor, they are different lenses highlighting different areas of the same landscape. Furthermore, it must be said that neither are sufficient in themselves, but the psychodynamic theorists of religion to be highlighted in this essay share deeply with Hogue's heading in American Immanence.II. A Problematic AssumptionIn emphasizing and attempting to explain4 the role of non-rational processes in the both individual and social processes of perception and organization of experience, psychodynamic theories confound a widely held and problematic assumption that the triumph of rational analysis is the hallmark for building the society to which we should aspire. Political theory in general, [End Page 45] especially as it has taken its cues from a rationalist legacy about the inherently liberating force of Reason, has been weighted toward an assumption that its task of exposing the mystifications of power would suffice in inspiring more "rational" and therefore necessarily equitable social organization. This speaks to the longstanding socio-political interest in "consciousness raising" tactics, which are often meant to dispel "false consciousness." It even comes across in the emphases of Deweyan pragmatists on education. Psychologists of all stripes point out that this approach... (shrink)

A. W. Price explores the varying ways in which context is relevant to our reasoning about what to do.

Publicación compilatoria que recoge los avances que en los últimos tiempos se han producido en materia normativa sobre acceso a los recursos genéticos, en un intento por implementar los principios del Convenio sobre la Diversidad Biológica (1992).

Ludwig Wittgenstein (1889-1951) was an extraordinarily original thinker, whose influence on twentieth-century thinking far outside the bounds of philosophy alone. In this engaging Introduction, A.C. Grayling makes Wittgenstein's thought accessible to the general reader by explaining the nature and impact of Wittgenstein's views. He describes both his early and later philosophy, the differences and connections between them, and gives a fresh assessment of Wittgenstein's continuing influence on contemporary thought.

The elephant in the room -- Crabs and octopuses -- The central intelligence of a frog -- The cerebral cortex and consciousness -- Social consciousness -- Yoda and Darth: how can we find -- Consciousness in the brain? -- The hard problem and other perspectives on consciousness -- Conscious machines -- Uploading minds -- How to build visual consciousness.

The Human A Priori is a collection of essays by A. W. Moore, one of them previously unpublished and the rest all revised. These essays are all concerned, more or less directly, with something ineliminably anthropocentric in our systematic pursuit of a priori sense-making. Part I deals with the nature, scope, and limits of a priori sense-making in general. Parts II, III, and IV deal with what are often thought to be the three great exemplars of the systematic pursuit of (...) such sense-making: philosophy in the case of Part II, ethics in the case of Part III, and mathematics in the case of Part IV. Much of the attention throughout is devoted to the work of other philosophers: Kant and Wittgenstein feature prominently, and five of the essays take the form of reviews or critical notices of recent work in philosophy. But the interest in never purely exegetical. One of the lessons that emerges from the essays, either in opposition to the views of these other philosophers or by invocation of their views, is that we humans achieve nothing of real significance in philosophy, ethics, or mathematics except from a human point of view, and hence that all three of these pursuits can be said to betoken what may reasonably be called 'the human a priori'. (shrink)

For many Christians, personal experiences of God provide an important ground or justification for accepting the truth of the gospel. But we are sometimes mistaken about our experiences, and followers of other religions also provide impressive testimonies to support their religious beliefs. This book explores from a philosophical and theological perspective the viability of divine encounters as support for belief in God, arguing that some religious experiences can be accepted as genuine experiences of God and can provide evidence for Christian (...) beliefs. (shrink)