Online research in philosophy

This book is about how to understand quantum mechanics by means of a modal interpretation. Modal interpretations provide a general framework within which quantum mechanics can be considered as a theory that describes reality in terms of physical systems possessing definite properties. Quantum mechanics is standardly understood to be a theory about probabilities with which measurements have outcomes. Modal interpretations are relatively new attempts to present quantum mechanics as a theory which, like other physical theories, describes an observer-independent reality. In this book, Pieter Vermaas summarises the results of this work. The book will be of great value to undergraduates, graduate students and researchers in philosophy of science, and physics departments with an interest in learning about modal interpretations of quantum mechanics.

Quantum theory is highly successful in explaining properties of classes of systems: e.g. chemistry --- molecular binding energies optics --- frequency-dependent susceptibilities superconductivity --- energy gaps nuclear magnetic resonance --- chemical shifts particle physics --- scattering cross-sections cosmology --- helium abundance but many questions arise: What does quantum theory tell us about the nature of reality? Is quantum theory universally valid? Can quantum theory describe individual events? Can quantum theory be applied consistently at the macroscopic level? Is an algorithmic treatment of measurement theory possible? Is it possible to provide an interpretation of quantum theory which is compatible with special relativity/ general relativity/ quantum field theory/ this week's theory of everything?

This paper attempts to build a bridge between the interpretation of quantum theory and the philosophy of mind. In contrast to other such attempts, the bridge which this paper suggests does not consist in extending features of quantum theory to the philosophy of mind. The argument of this paper is that the discussion about a revision of the Cartesian tradition in current philosophy of mind is relevant to the interpretation of quantum theory: taking this discussion into account sharpens up the task for the interpretation of quantum physics as far as the scope of what is known as quantum holism is concerned. In particular, considering this discussion makes out a strong case against the interpretation that considers quantum holism to be universal in the physical realm.

A fully micro realistic, propensity version of quantum theory is proposed, according to which fundamental physical entities - neither particles nor fields - have physical characteristics which determine probabilistically how they interact with one another (rather than with measuring instruments). The version of quantum "smearon" theory proposed here does not modify the equations of orthodox quantum theory: rather, it gives a radically new interpretation to these equations. It is argued that (i) there are strong general reasons for preferring quantum "smearon" theory to orthodox quantum theory; (ii) the proposed change in physical interpretation leads quantum "smearon" theory to make experimental predictions subtly different from those of orthodox quantum theory. Some possible crucial experiments are considered.

A physical and mathematical framework for the analysis of probabilities in quantum theory is proposed and developed. One purpose is to surmount the problem, crucial to any reconciliation between quantum theory and space-time physics, of requiring instantaneous "wave-packet collapse" across the entire universe. The physical starting point is the idea of an observer as an entity, localized in space-time, for whom any physical system can be described at any moment, by a set of (not necessarily pure) quantum states compatible with his observations of the system at that moment. The mathematical starting point is the theory of local algebras from axiomatic relativistic quantum field theory. A function defining the a priori probability of mistaking one local state for another is analysed. This function is shown to possess a broad range of appropriate properties and to be uniquely defined by a selection of them. Through a general model for observations, it is argued that the probabilities defined here are as compatible with experiment as the probabilities of conventional interpretations of quantum mechanics but are more likely to be compatible, not only with modern developments in mathematical physics, but also with a complete and consistent theory of measurement.

Mainstream cognitive neuroscience typically ignores the role of quantum physical effects in the neural processes underlying cogni¬tion and consciousness. However, many unsolved problems remain, suggesting the need to consider new approaches. We propose that quantum theory, especially through an ontological interpretation due to Bohm and Hiley, provides a fruitful framework for addressing the neural correlates of cognition and consciousness. In particular, the ontological interpretation suggests that a novel type of 'active information', connected with a novel type of 'quantum potential energy', plays a key role in quantum physical processes. After introducing the ontological interpretation we illustrate its value for cognitive neuroscience by discussing it in the light of a proposal by Beck and Eccles about how quantum tunneling could play a role in controlling the frequency of synaptic exocytosis. In this proposal, quantum tunneling would enable the 'self' to control its brain without violating the energy conservation law. We argue that the ontological interpretation provides a sharper picture of what actually could be taking place in quantum tunneling in general and in synaptic exocytosis in particular. Based on the notions of active information and quantum potential energy, we propose a coherent way of understanding how mental processes (understood as involving non-classical physical processes) can act on traditional, classically describable neural processes without violating the energy conservation law.

Confused ideas about the weirdness of quantum mechanics have sometimes been blamed for the spread of anti-realist positions in philosophy. In this seminar, I shall re-examine the relation between realism and quantum theory. My goal is to argue that one can remain a realist in a reasonably familiar sense, while adopting a theory which amounts to a form of idealism. After sketching the abstract mathematical structure of quantum theory, I will introduce realism and consider some of its problems and some counter-arguments. Next I will look at why quantum theory needs an interpretation and at some of the features common to many proposed interpretations. Then I will discuss some of the gaps in decoherence theory, when it is considered as an interpretation of quantum theory, and I will end with a sketch of my own realist version of idealism in which the fundamental entities are structures which define minds, and the fundamental laws govern the stochastic developments of those structures.

How come quantum theory has anything to do with mind? Is your theory refutable? What is the point of all the technical detail? Do you suggest that the operation of the brain involves large scale quantum coherence? Isn't large scale quantum coherence necessary to solve the problem of the unity of consciousness? How does a many-minds interpretation survive Occam's razor? What, briefly, is your current philosophical position? What is your understanding of the relationship between mind and brain for split-brain patients? Do you believe that the mind can survive the death of the brain? No journal reference is given for several of the recent papers on your home page. Where will these papers be printed? How are the “source” and “pdf” versions of the papers on your home page produced and viewed? Why does the page with your photograph behave oddly in some browsers? Where can I find an elementary introduction to the interpretation of quantum theory? Doesn't decoherence theory solve all the problems of the interpretation of quantum theory? How do the ambiguities of decoherence affect the many-worlds interpretation? Could you expand on your answers to the two previous questions? Why isn't the conventional interpretation of quantum theory adequate? What about the Bohm interpretation? What about consistent histories? Does the present many-minds interpretation solve all the problems?

Orthodox Copenhagen quantum theory renounces the quest to understand the reality in which we are imbedded, and settles for practical rules that describe connections between our observations. Many physicist have believed that this renunciation of the attempt describe nature herself was premature, and John von Neumann, in a major work, reformulated quantum theory as a theory of the evolving objective universe. In the course of his work he converted to a benefit what had appeared to be a severe deficiency of the Copenhagen interpretation, namely its introduction into physical theory of the human observers. He used this subjective element of quantum theory to achieve a significant advance on the main problem in philosophy, which is to understand the relationship between mind and matter. That problem had been tied closely to physical theory by the works of Newton and Descartes. The present work examines the major problems that have appeared to block the development of von Neumann’s theory into a fully satisfactory theory of Nature, and proposes solutions to these problems.