Nick Huggett

Weyl symmetry of the classical bosonic string Lagrangian is broken by quantization, with profound consequences described here. Reimposing symmetry requires that the background space-time satisfy the equations of general relativity: general relativity, hence classical space-time as we know it, arises from string theory. We investigate the logical role of Weyl symmetry in this explanation of general relativity: it is not an independent physical postulate but required in quantum string theory, so from a certain point of view it plays only a formal role in the explanation

The positivistic Received View construed scientific theories syntactically as axiomatic calculi where theoretical terms were given a partial semantic interpretation via correspondence rules connecting them to observation statements. This paper assesses what, with hindsight, seem the most important defects in the Received View; surveys the main proposed successor analyses to the Received View—various Semantic Conception versions and the Structuralist Analysis; evaluates how well they avoid those defects; examines what new problems they face and where the most promising require further development or leave unanswered questions; explores implications of recent work on models for understanding theories; and rebuts the few criticisms of the Semantic Conception that have surfaced.

The two books discussed here make important contributions to our understanding of the role of spacetime concepts in physical theories and how that understanding has changed during the evolution of physics. Both emphasize what can be called a ‘dynamical’ account, according to which geometric structures should be understood in terms of their roles in the laws governing matter and force. I explore how the books contribute to such a project; while generally sympathetic, I offer criticisms of some historical claims concerning Newton, and argue that the dynamical account does not undercut ontological issues as the books claim.

Learning through original texts can be a powerful heuristic tool. This book collects a dozen classic readings that are generally accepted as the most significant contributions to the philosophy of space. The readings have been selected both on the basis of their relevance to recent debates on the nature of space and on the extent to which they carry premonitions of contemporary physics. In his detailed commentaries, Nick Huggett weaves together the readings and links them to our modern understanding of the subject. Together the readings indicate the general historical development of the concept of space, and in his commentaries Huggett explains their logical relations. He also uses our contemporary understanding of space to help clarify the key ideas of the texts. One goal is to prepare the reader (both scientist and nonscientist) to learn and understand relativity theory, the basis of our current understanding of space. The readings are by Zeno, Plato, Aristotle, Euclid, Descartes, Newton, Leibniz, Clarke, Berkeley, Kant, Mach, Poincaré, and Einstein.

Why is our knowledge of the past so much more ‘expansive’ (to pick a suitably vague term) than our knowledge of the future, and what is the best way to capture the difference(s) (i.e., in what sense is knowledge of the past more ‘expansive’)? One could reasonably approach these questions by giving necessary conditions for different kinds of knowledge, and showing how some were satisfied by certain propositions about the past, and not by corresponding propositions about the future. I take it that such is the approach of Chapter 6 of Time and Chance (T&C). Here’s another such a proposal, similar to that of, but significantly different from T&C; my purpose in this section is to highlight the differences, by showing how this account fails.

Since the collapse of the 'received view' consensus in the late 1960s, the question of scientific realism has been a major preoccupation of philosophers of science. This paper sketches the history of this debate, which grew from developments in the philosophy of language, but eventually took on an autonomous existence. More recently, the debate has tended towards more 'local' considerations of particular scientific episodes as a way of getting purchase on the issues. The paper reviews two such approaches, Fine's and Hacking's, describing their positions, their prospects, and how they are related. Finally, the paper suggests that local philosophies of science offer a way for our discipline to engage more fruitfully with the public and the scientific community

This paper explains the phenomenon of `entanglement exchange' within the Bohmian approach to quantum mechanics. After explaining Bohmian mechanics and entanglement exchange, in which pairs of particles become entangled without ever interacting causally in the usual, unitary sense, our aim is to use this example, to illustrate how the `pilot wave' mediates non-local correlations. The discussion thus gives a useful new way to think about entanglement exchange, and clarifies the structure of Bohmian mechanics

This item is a chapter from a book in progress, entitled "True Motion". Leibniz’s mechanics was, as we shall see, a theory of elastic collisions, not formulated like Huygens’ in terms of rules explicitly covering every possible combination of relative masses and velocities, but in terms of three conservation principles, including (effectively) the conservation of momentum and kinetic energy. That is, he proposed what we now call (ironically enough) ‘Newtonian’ (or ‘classical’) elastic collision theory. While such a theory is, for instance, vital to the foundations of the kinetic theory of gases, it is not applicable to systems – like gravitational systems – in which fields of force are present. Thus, Leibniz’s mechanical principles never led to developments of the order of Newton’s in the Principia (additionally, he hamstrung their application by embedding them in a baroque philosophical system).

I criticize a certain view of the 'quanta' of quantum mechanics that sees them as fundamentally non-atomistic and fundamentally significant for our understanding of quantum fields. In particular, I have in mind work by Redhead and Teller (1991, 1992 and Teller 1990). I prove that classical particles do not have the rather strong flavour of identity often associated with them; permuting positions and momenta does not produce distinct states. I show that even the label free excitation formalism is compatible with a mild form of atomism. Finally, I summarise some of the principle objections to an 'oscillator' interpretation of quantum fields.

This paper investigates the mathematical representation of time in physics. In existing theories time is represented by the real numbers, hence their formal proper- ties represent properties of time: these are surveyed. The central question of the paper is whether the existing representation of time is adequate, or whether it can or should be supplemented: especially, do we need a physics incorporating some kind of ‘dynamical passage’ of time? The paper argues that the existing mathematical framework is resistant to such changes, and might have to be rejected by anyone seeking a physics of passage. Then it rebuts two common arguments for incorporating passage into physics, especially the claim that it is an element of experience. Finally the paper investigates whether, as has been claimed, ‘causal set theory’ provides a physics of passage.

Newton's arguments for the immobility of the parts of absolute space have been claimed to licence several proposals concerning his metaphysics. This paper clarifies Newton, first distinguishing two distinct arguments. Then, it demonstrates, contrary to Nerlich ([2005]), that Newton does not appeal to the identity of indiscernibles, but rather to a view about de re representation. Additionally, DiSalle ([1994]) claims that one argument shows Newton to be an anti-substantivalist. I agree that its premises imply a denial of a kind of substantivalism, but I show that they are inconsistent with Newton's core doctrine that not all motion is the relative motions of bodies, and so conclude that they are not part of his considered views on space. The Arguments The Identity Argument 2.1 Identity of indiscernibles for individuals 2.2 Identity of indiscernibles for worlds and states 2.3 Representation de re Kinematic Relationism Conclusion CiteULike    Connotea    Del.icio.us    What's this?

A number of commentators (especially French and Redhead, 1988, and Butterfield, 1993) have investigated the status of the principle of the identity of indiscernibles (PII) for bosons and fermions. In this paper I extend that investigation to the full range of quantum particles of any allowed kind of statistics -- `quarticles', that is. I show that for any kind (except bosons and fermions) there are states in which PII is violated by every pair of particles, some pairs and not others, and by no pairs.

Since antiquity, natural philosophers have struggled to comprehend the nature of three tightly interconnected concepts: space, time, and motion. A proper understanding of motion, in particular, has been seen to be crucial for deciding questions about the natures of space and time, and their interconnections. Since the time of Newton and Leibniz, philosophers’ struggles to comprehend these concepts have often appeared to take the form of a dispute between absolute conceptions of space, time and motion, and relational conceptions. This article guides the reader through some of the history of these philosophical struggles. Rather than taking sides in the (alleged) ongoing debates, or reproducing the standard dialectic recounted in most introductory texts, we have chosen to scrutinize carefully the history of the thinking of the canonical participants in these debates — principally Descartes, Newton, Leibniz, Mach and Einstein. Readers interested in following up either the historical questions or current debates about the natures of space, time and motion will find ample links and references scattered through the discussion and in the Other Internet Resources section below.

Where should we begin our story? Many books start with Newton, but Newton was responding to both Galileo1 and especially (for our purposes) Descartes. But Galileo and Descartes themselves were writing in the context of late Aristotelianism, and so were trained in and critical of that rich school of thought, so if we want to fully understand their work we would need to understand scholastic views on space and motion (see Grant, 1974, Murdoch and Sylla, 1978 and Ariew and Gabbey, 1998). But late scholasticism itself is the result of a long history tracing from Plato and Aristotle through Jewish, Arabic, Islamic and European thought. And of course Plato and Aristotle are explicitly reacting to their predecessors and contemporaries. In other words, we could start the story as early in recorded thought as we like.