Foundations of Space-Time Theories, by Michael Friedman, falls naturally into two parts. In the first, he presents the general framework within which he will characterize and discuss space-time theories, and then he devotes a chapter each to Newtonian physics, special relativity, and general relativity. Although there is some rich philosophical discussion along the way, these chapters are, of necessity, somewhat technical expositions of the general framework in action. It is in the second part, consisting of two substantial chapters, one on (...) relationalism, the other on conventionalism, that more general philosophical issues are addressed. (shrink)

In this paper I first describe some simple, but interesting string theory. Then I discuss string field theory and suggest that even though we do not have a complete mathematical formulation, we can get an idea of some of its ontological implications. Next, the significance of supersymmetry and superspace in string theory is briefly considered. Lastly, I consider the question of whether there is, in fact, (good) reason to think string theory may (or will) emerge to replace quantum field theory.

In this paper we will take a careful look at the well-known fact that a complete 2 rotation in three dimensional space, while leaving vectors, tensors and generally the integral representations of the rotation group unchanged, causes a sign change in the half-integral spinor representations of the rotation group. First, in a brief introduction, we review the origin of the sign change of spinors by a 2 rotation. Next, we analyze Aharonov and Susskind's (hereafter referred to as A. & S.) (...) (1967) original proposal for detecting such a sign change and compare it with a later proposal1 for detecting the sign change using neutron beams that are coherently split and recombined. While the A. & S. experiment is, we think, conceptually more interesting, the neutron beam experiment has actually been carried out. And finally, we discuss the philosophical significance of the rotationally induced spinor sign change. (shrink)

In this paper a few facts about Feynman diagrams and the perturbation expansion of the S-matrix are reviewed and discussed in connection with the question of the ontological status of virtual particles.

We must conclude, from the above discussion, that Putnam has not satisfactorily explained how a person can go back in time and thus has not offered any compelling reason why we should accept his description of Oscar rather than his objector's description. However, earlier in our discussion, a possible way to show that Oscar did go back in time came to light: namely, if it could be shown that Oscar2 was at B at t 1 because Oscar1 entered the time (...) machine at t 2. Thus, if backward causation were possible, such backward causes could be used to send a person back in time. But whether backward causation is a conceptual possibility or not is the topic for another paper. (shrink)

It has been suggested by several philosophers that many of the so-called paradoxes of backward time travel can be resolved if we conceive of the backward time traveller as having a zig-zag or N-shaped world line in spacetime. In this I am in general agreement. But there is still a problem in conceiving of backward time travel this way. In this note I will show how we can solve this problem by conceiving of backward time travel in terms of the (...) closed time-like world lines in certain general relativistic space-times. Indeed, it has often been claimed that such world models as Godei spacetime show that backward time travel is conceivable. Our discussion will help to make clear just why this claim is correct. (shrink)

Recently, Michael Redhead has argued that the grouping of particles into multiplets by grand unified gauge theories (GUT's) does not, by itself, imply an ontological reduction in the number of elementary particles. While sympathetic to Redhead's argument, in this note I argue that under certain conditions involving Kaluza-Klein theories, GUT's would provide such an ontological reduction.

Much apprehension has been expressed by philosophers about the method of renormalisation in quantum field theory, as it apparently requires illegitimate procedure of infinite cancellation. This has lead to various speculations, in particular in Teller (1989). We examine Teller's discussion of perturbative renormalisation of quantum fields, and show why it is inadequate. To really approach the matter one needs to understand the ideas and results of the renormalisation group, so we give a simple but comprehensive account of this topic. With (...) this in hand, we explain how renormalisation can and should be understood. One thing that is revealed is that apparently very successful theories such as quantum electro-dynamics cannot be universally true; resolving the tension between success and falsity leads to a picture in which any theory may be viewed as irreducibly phenomenological. We explain how, and argue that the support for this view is tenuous at best. (shrink)

Topology is a kind of abstraction from metrical geometry. The metrical geometry is the distance geometry of a space and gives rise to concepts such as length, angles, and curvature. Topology studies spaces with a much more general conception of “nearness” than that provided by the metric. Thus, although the metric geometry distinguishes spheres, cubes, and pyramids from one another due to their different metrical properties, topology classifies them together as instances of the same object. However, topology does mark a (...) difference between spheres and doughnuts since, loosely speaking, “holes” are topological properties. Explaining the difference between topological and metrical properties is therefore the natural first order of business when introducing the ideas of topology. (shrink)

As recently documented in J. Cushing’s excellent book, throughout its almost fifty-year history, Bohm’s interpretation of quantum mechanics has been systematically misunderstood and ignored. On the rare occasions it was examined, it was usually dismissed for reasons having more to do with politics, religion, positivism, and sloppy thought, than for reasons central to physics. In recent times, however, Bohm’s theory has received much more serious attention from physicists and philosophers, thanks mainly to J. S. Bell’s positive influence on the theory. (...) Most of this work reacts favorably toward Bohm’s theory. And this is not surprising, for Bohm’s theory provides us with a consistent, empirically adequate picture of the quantum world. (shrink)

Throughout its history, Bohm's interpretation of quantum mechanics has been systematically misunderstood and ignored. It was often dismissed for reasons having more to do with politics, religion, positivism, and sloppy thought, than for reasons central to physics. Still, like any physical theory, Bohm's theory faces challenges of varying degrees of severity. Here we review and evaluate some of these challenges.

Must space be a unity? This question, which exercised Aristotle, Descartes and Kant, is a specific instance of a more general one; namely, can the topology of physical space change with time? In this paper we show how the discussion of the unity of space has been altered but survives in contemporary research in theoretical physics. With a pedagogical review of the role played by the Euler characteristic in the mathematics of relativistic spacetimes, we explain how classical general relativity (modulo (...) considerations about energy conditions) allows virtually unrestrained spatial topology change in four dimensions. We also survey the situation in many other dimensions of interest. However, topology change comes with a cost: a famous theorem by Robert Geroch shows that, for many interesting types of such change, transitions of spatial topology imply the existence of closed timelike curves or temporal non-orientability. Ways of living with this theorem and of evading it are discussed. (shrink)

A realist causal model of quantum cosmology (QC) is developed. By applying the de Broglie-Bohm interpretation of quantum mechanics to QC, we resolve the notorious 'problem of time' in QC, and derive exact equations of motion for cosmological dynamical variables. Due to this success, it is argued that if the situation in QC is used as a yardstick by which other interpretations are measured, the de Broglie-Bohm theory seems uniquely fit as an interpretation of quantum mechanics.

Onc of thc problems of quantnun cosmology follows from thc fact that thc Hamiltonian H of classical general relativity equals zero. Quantizing canonically in thc Schrodinger picture, thc Schrodinger equation for thc wave function *1* of thc universe is thcreforc thc so-called Whcelc:r—DeWitt..

Foundations of Space-Time Theories, by Michael Friedman, falls naturally into two parts. In the first, he presents the general framework within which he will characterize and discuss space-time theories, and then he devotes a chapter each to Newtonian physics, special relativity, and general relativity. Although there is some rich philosophical discussion along the way, these chapters are, of necessity, somewhat technical expositions of the general framework in action. It is in the second part, consisting of two substantial chapters, one on (...) relationalism, the other on conventionalism, that more general philosophical issues are addressed. (shrink)

In this paper we critically review the various attempts that have been made to understand quantum field theory. We focus on Teller's (1990) harmonic oscillator interpretation, and Bohm et al.'s (1987) causal interpretation. The former unabashedly aims to be a purely heuristic account, but we show that it is only interestingly applicable to the free bosonic field. Along the way we suggest alternative models. Bohm's interpretation provides an ontology for the theory--a classical field, with a quantum equation of motion. This (...) too has problems; it is not Lorentz invariant. (shrink)

The Einstein-Podolsky-Rosen (EPR) paradox and the correlated states it introduced comprise one of the central interpretive problems of quantum mechanics. Because of the apparent nonlocal character of this paradox, it should be given a relativistic treatment. The purpose of this paper is to provide such a treatment.

In this note a recently developed quantum oscillating finite space cosmological model is described. The principle novelty of the model is that there is a quantum blurring of the classical singularity between cycles, instead of a singularity free bounce. Recently, Quentin Smith (1988) has argued that present theoretical and observational evidence justifies the belief that the past history of the universe is finite. The relevance of this cosmological model to Smith's arguments is discussed.

Paul Teller's new book, “An Interpretive Introduction to Quantum Field Theory”, is a pioneering work. To the best of our knowledge it is the first book by a philosopher devoted not only to explaining what quantum field theory is, but to clarifying the conceptual issues and puzzles to which the theory gives rise. As such it is an important book, which we hope will greatly stimulate work in the area as other philosophers and physicists react to it.

Paul Teller's new book, “An Interpretive Introduction to Quantum Field Theory”, is a pioneering work. To the best of our knowledge it is the first book by a philosopher devoted not only to explaining what quantum field theory is, but to clarifying the conceptual issues and puzzles to which the theory gives rise. As such it is an important book, which we hope will greatly stimulate work in the area as other philosophers and physicists react to it.

In this paper we contrast the idea of a field as a system with an infinite number of degrees of freedom with a recent alternative proposed by Paul Teller in Teller (1990). We show that, although our characterisation lacks the immediate appeal of Teller's, it has more success producing agreement with intuitive categorisations than his does. We go on to extend the distinction to Quantum Mechanics, explaining the important role that it plays there. Finally, we take some time to investigate (...) the way in which strings are to be considered fields, and the important differences with scalar fields. Overall, we aim to show that many types of systems may be viewed as fields, and to point out significant distinctions amongst them, thereby expanding our understanding of what it is to fall in this category. (shrink)

We explicate recent results that shed light on the obscure and troubling problem of renormalization in Quantum Field Theory (QFT). We review how divergent predictions arise in perturbative QFT, and how they are renormalized into finite quantities. Commentators have worried that there is no foundation for renormalization, and hence that QFTs are not logically coherent. We dispute this by describing the physics behind liquid diffusion, in which exactly analogous divergences are found and renormalized. But now we are looking at a (...) problem that is physically and formally well-defined, proving that the problems of renormalization, by themselves, cannot refute QFT. (shrink)

We explicate recent results that shed light on the obscure and troubling problem of renormalization in Quantum Field Theory. We review how divergent predictions arise in perturbative QFT, and how they are renormalized into finite quantities. Commentators have worried that there is no foundation for renormalization, and hence that QFTs are not logically coherent. We dispute this by describing the physics behind liquid diffusion, in which exactly analogous divergences are found and renormalized. But now we are looking at a problem (...) that is physically and formally well-defined, proving that the problems of renormalization, by themselves, cannot refute QFT. (shrink)

The abstract structure of inquiry - the process of acquiring and changing beliefs about the world - is the focus of this book which takes the position that the "pragmatic" rather than the "linguistic" approach better solves the philosophical problems about the nature of mental representation, and better accounts for the phenomena of thought and speech. It discusses propositions and propositional attitudes (the cluster of activities that constitute inquiry) in general and takes up the way beliefs change in response to (...) potential new information, suggesting that conditional propositions should be understood as projections of epistemic policies onto the world.Robert C. Stalnaker is a professor in the Sage School of Philosophy at Cornell University. A Bradford Book. (shrink)

Winner of the 1975 National Book Award, this brilliant and widely acclaimed book is a powerful philosophical challenge to the most widely held political and social positions of our age--liberal, socialist, and conservative.

Robert B. Brandom is one of the most original philosophers of our day, whose book Making It Explicit covered and extended a vast range of topics in metaphysics, epistemology, and philosophy of language--the very core of analytic philosophy. This new work provides an approachable introduction to the complex system that Making It Explicit mapped out. A tour of the earlier book's large ideas and relevant details, Articulating Reasons offers an easy entry into two of the main themes of Brandom's (...) work: the idea that the semantic content of a sentence is determined by the norms governing inferences to and from it, and the idea that the distinctive function of logical vocabulary is to let us make our tacit inferential commitments explicit. Brandom's work, making the move from representationalism to inferentialism, constitutes a near-Copernican shift in the philosophy of language--and the most important single development in the field in recent decades. Articulating Reasons puts this accomplishment within reach of nonphilosophers who want to understand the state of the foundations of semantics. Table of Contents: Introduction 1. Semantic Inferentialism and Logical Expressivism 2. Action, Norms, and Practical Reasoning 3. Insights and Blindspots of Reliabilism 4. What Are Singular Terms, and Why Are There Any? 5. A Social Route from Reasoning to Representing 6. Objectivity and the Normative Fine Structure of Rationality Notes Index Displaying a sovereign command of the intricate discussion in the analytic philosophy of language, Brandom manages successfully to carry out a program within the philosophy of language that has already been sketched by others, without losing sight of the vision inspiring the enterprise in the important details of his investigation ' Using the tools of a complex theory of language, Brandom succeeds in describing convincingly the practices in which the reason and autonomy of subjects capable of speech and action are expressed. --J'rgen Habermas. (shrink)

In a new retelling of the romantic rationalist adventure of ideas that is Hegel's classic The Phenomenology of Spirit, Robert Brandom argues that when our self-conscious recognitive attitudes take Hegel's radical form of magnanimity and trust, we can overcome a troubled modernity and enter a new age of spirit.

Winner of the Los Angeles Times Book Prize With a new preface by the author In his most powerful and important book, renowned psychiatrist Robert Jay Lifton presents a brilliant analysis of the crucial role that German doctors played in the Nazi genocide. Now updated with a new preface, The Nazi Doctors remains the definitive work on the Nazi medical atrocities, a chilling exposé of the banality of evil at its epitome, and a sobering reminder of the darkest side (...) of human nature. (shrink)

This paper revisits some foundational questions concerning the abstract representation of a discourse context. The context of a conversation is represented by a body of information that is presumed to be shared by the participants in the conversation – the information that the speaker presupposes a point at which a speech act is interpreted. This notion is designed to represent both the information on which context-dependent speech acts depend, and the situation that speech acts are designed to affect, and so (...) to be a representation of context that is appropriate for explaining the interaction of context and the contents expressed in them. After reviewing the motivating ideas and the outlines of the apparatus, the paper responds to a criticism of the framework, and considers the way it can help to clarify some phenomena concerning pronouns with indefinite antecedents. (shrink)