The priority of internal symmetries in particle physics

In this paper, I try to decipher the role of internal symmetries in the ontological maze of particle physics. The relationship between internal symmetries and laws of nature is discussed within the framework of “Platonic realism.” The notion of physical “structure” is introduced as representing a deeper ontological layer behind the observable world. I argue that an internal symmetry is a structure encompassing laws of nature. The application of internal symmetry groups to particle physics came about in two revolutionary steps. The first was the introduction of the internal symmetries of hadrons in the early 1960s. These global and approximate symmetries served as means of bypassing the dynamics. I argue that the realist could interpret these symmetries as ontologically prior to the hadrons. The second step was the gauge revolution in the 1970s, where symmetries became local and exact and were integrated with the dynamics. I argue that the symmetries of the second generation are fundamental in the following two respects: (1) According to the so-called “gauge argument,” gauge symmetry dictates the existence of gauge bosons, which determine the nature of the forces. This view, which has been recently criticized by some philosophers, is widely accepted in particle physics at least as a heuristic principle. (2) In view of grand unified theories, the new symmetries can be interpreted as ontologically prior to baryon matter.     

Why the Afshar experiment does not refute complementarity

A modified version of Young's experiment by Shahriar Afshar demonstrates that, prior to what appears to be a “which-way” measurement, an interference pattern exists. Afshar has claimed that this result constitutes a violation of the Principle of Complementarity. This paper discusses the implications of this experiment and considers how Cramer's Transactional Interpretation easily accommodates the result. It is also shown that the Afshar experiment is analogous in key respects to a spin one-half particle prepared as “spin up along x”, subjected to a nondestructive confirmation of that preparation, and post-selected in a specific state of spin along z. The terminology “which-way” or “which-slit” is critiqued; it is argued that this usage by both Afshar and his critics is misleading and has contributed to confusion surrounding the interpretation of the experiment. Nevertheless, it is concluded that Bohr would have had no more problem accounting for the Afshar result than he would in accounting for the aforementioned pre- and post-selection spin experiment, in which the particle's preparation state is confirmed by a nondestructive measurement prior to post-selection. In addition, some new inferences about the interpretation of delayed choice experiments are drawn from the analysis.     

Mechanisms, principles, and Lorentz's cautious realism

I show that Albert Einstein's distinction between principle and constructive theories was predated by Hendrik A. Lorentz's equivalent distinction between mechanism- and principle-theories. I further argue that Lorentz's views toward realism similarly prefigure what Arthur Fine identified as Einstein's “motivational realism.”     

On the necessary truth of the laws of classical mechanics

The idealization of primitive mechanical experience is shown to lead to four mutually related formulations of classical mechanics based on connections, action at a distance, stresses, and collisions. For a given structure of spacetime and a given characterization of mechanical systems, fundamental laws (including Newton's law of acceleration and d’Alembert's principle) are derived from a few general principles regarding the comprehensibility of motion. Special emphasis is placed on the “secular principle,” according to which the evolution of a system at the relevant time scale should not depend on finer details of the applied forces.     

The epistemology of hedged laws

Standard objections to the notion of a hedged, or ceteris paribus, law of nature usually boil down to the claim that such laws would be either (1) irredeemably vague, (2) untestable, (3) vacuous, (4) false, or a combination thereof. Using epidemiological studies in nutrition science as an example, I show that this is not true of the hedged law-like generalizations derived from data models used to interpret large and varied sets of empirical observations. Although it may be ‘in principle impossible’ to construct models that explicitly identify all potential causal interferers with the relevant generalization, the view that our failure to do so is fatal to the very notion of a cp-law is plausible only if one illicitly infers metaphysical impossibility from epistemic impossibility. I close with the suggestion that a model-theoretic approach to cp-laws poses a problem for recent attempts to formulate a Mill–Ramsey–Lewis theory of cp-laws.     

Experiment versus mechanical philosophy in the work of Robert Boyle: a reply to Anstey and Pyle

We can distinguish ‘mechanical’ in the strict sense of the mechanical philosophers from ‘mechanical’ in the common sense. My claim is that Boyle's experimental science owed nothing to, and offered no support for, the mechanical philosophy in the strict sense. The attempts by my critics to undermine my case involve their interpreting ‘mechanical’ in something like the common sense. I certainly accept that Boyle's experimental science was productively informed by mechanical analogies, where ‘mechanical’ is interpreted in a common sense. But this leaves my original claim untouched and, in the main, unchallenged.     

Introduction

The question of the existence of intelligent life on other worlds has never been a purely scientific one. Philosophical, religious and literary issues have been intertwined with scientific ones throughout the history of the “plurality of worlds” debate. This collection of papers in –Studies in History and Philosophy of Science– explores the interrelation of science, philosophy, religion and literature in debates about extraterrestrial life.     

Measuring constants of nature: confirmation and determination in piezoelectricity

Exact measurements are a central practice of modern physics. In certain cases, they are essential for determining values of coefficients, for confirming theories, and for detecting the existence of effects. The history of piezoelectricity at the end of the nineteenth century reveals two different methods of exact measurement: a mathematical versus an “artisanal” approach. In the former, a scientist first carried out the experiment and later employed mathematical methods to reduce error. In the latter, a scientist physically manipulated the experimental apparatus to bypass possible sources of error before its performance. These two approaches were related to German theoreticians and to French experimentalists, respectively. However, affiliation with a particular school rather than nationality was the decisive factor in the differences between the two approaches. Despite differences, adherents of both approaches sought to attain high precision and to eliminate even small experimental errors.This history exhibits the complexity and flexibility of experiments and their analysis. It supports the claim of the “New Experimentalism” that theory does not supply complete directions for practical experimental decisions. An example for this is found in the way an experimental error was discovered (after incorrect results had already been published) only by a comparison to an earlier experiment rather than to a theory.     

Did Einstein prove E=mc2?

Although Einstein's name is closely linked with the celebrated relation E=mc² between mass and energy, a critical examination of the more than half dozen “proofs” of this relation that Einstein produced over a span of forty years reveals that all these proofs suffer from mistakes. Einstein introduced unjustified assumptions, committed fatal errors in logic, or adopted low-speed, restrictive approximations. He never succeeded in producing a valid general proof applicable to a realistic system with arbitrarily large internal speeds. The first such general proof was produced by Max Laue in 1911 (for “closed” systems with a time-independent energy–momentum tensor) and it was generalized by Felix Klein in 1918 (for arbitrary time-dependent “closed” systems).     

A philosophical study of the transition from the caloric theory of heat to thermodynamics: Resisting the pessimistic meta-induction

I began this study with Laudan's argument from the pessimistic induction and I promised to show that the caloric theory of heat cannot be used to support the premisses of the meta-induction on past scientific theories. I tried to show that the laws of experimental calorimetry, adiabatic change and Carnot's theory of the motive power of heat were (i) independent of the assumption that heat is a material substance, (ii) approximately true, (iii) deducible and accounted for within thermodynamics.I stressed that results (i) and (ii) were known to most theorists of the caloric theory and that result (iii) was put forward by the founders of the new thermodynamics. In other words, the truth-content of the caloric theory was located, selected carefully, and preserved by the founders of thermodynamics.However, the reader might think that even if I have succeeded in showing that laudan is wrong about the caloric theory, I have not shown how the strategy followed in this paper can be generalised against the pessimistic meta-induction. I think that the general strategy against Laudan's argument suggested in this paper is this: the empirical success of a mature scientific theory suggests that there are respects and degrees in which this theory is true. The difficulty for — and and real challenge to — philosophers of science is to suggest ways in which this truth-content can be located and shown to be preserved — if at all — to subsequent theories. In particular, the empirical success of a theory does not, automatically, suggest that all theoretical terms of the theory refer. On the contrary, judgments of referential success depend on which theoretical claims are well-supported by the evidence. This is a matter of specific investigation. Generally, one would expect that claims about theoretical entities which are not strongly supported by the evidence or turn out to be independent of the evidence at hand, are not compelling. For simply, if the evidence does not make it likely that our beliefs about putative theoretical entities are approximately correct, a belief in those entities would be ill-founded and unjustified. Theoretical extrapolations in science are indespensable , but they are not arbitrary. If the evidence does not warrant them I do not see why someone should commit herself to them. In a sense, the problem with empricist philisophers is not that they demand that theoretical beliefs must be warranted by evidence. Rather, it is that they claim that no evidence can warrant theorretical beliefs. A realist philosopher of science would not disagree on the first, but she has good grounds to deny the second.I argued that claims about theoretical entities which are not strongly supported by the evidence must not be taken as belief-worthy. But can one sustaon the more ambitious view that loosely supported parts of a theory tend to be just those that include non-referring terms? There is an obvious excess risk in such a generalisation. For there are well-known cases in which a theoretical claim was initially weakly supported by the evidence     

The cosmological constant, the fate of the universe, unimodular gravity, and all that

The cosmological constant is back. Several lines of evidence point to the conclusion that either there is a positive cosmological constant or else the universe is filled with a strange form of matter (“quintessence”) that mimics some of the effects of a positive lambda. This paper investigates the implications of the former possibility. Two senses in which the cosmological constant can be a constant are distinguished: the capital Λ sense in which lambda is a universal constant on a par with the charge of the electron, and the lower case λ sense in which lambda is a humble constant of integration. The latter interpretation has been touted as the means to a solution to various problems in physics. These claims are critically examined with an eye to discerning the implications for philosophy of science and foundations of physics.     

Energy conservation and supertasks

The most recent results in the dynamics of infinite systems of particles have shown there is no necessary connection between the performance of a deterministic supertask and the non-conservation of energy. Much more difficult to prove is the non-existence of any necessary connection between the performance of an indeterministic supertask and the non-conservation of energy; however, this paper does just that. So the requirement that energy be conserved does not mean we can exclude as “non-physical” either of the two major types of supertask considered to date. The paper also proposes, in this context, a “hidden variables method” to prove general results of compatibility in dynamics.     

Thomas Reid and the problem of induction: from common experience to common sense

By the middle of the eighteenth century the new science had challenged the intellectual primacy of common experience in favor of recondite, expert and even counter-intuitive knowledge increasingly mediated by specialized instruments. Meanwhile modern philosophy had also problematized the perceptions of common experience — in the case of David Hume this included our perception of causal relations in nature, a fundamental precondition of scientific endeavor.In this article I argue that, in responding to the ‘problem of induction’ as advanced by Hume, Reid reformulated Aristotelian foundationalism in distinctly modern terms. An educator and mathematician self-consciously working within the framework of the new science, Reid articulated a philosophical foundation for natural knowledge anchored in the human constitution and in processes of adjudication in an emerging modern public sphere of enlightened discourse. Reid thereby transformed one of the bases of Aristotelian science — common experience — into a philosophically and socially justified notion of ‘common sense’. Reid's intellectual concerns had as much to do with the philosophy of science as they did with moral philosophy or epistemology proper, and were bound up with wider social and scientific changes taking place in the early modern period.     

Symmetry and asymmetry in electrodynamics from Rowland to Einstein

Halfway through the paper in which he laid down the foundations for the theory of special relativity, Einstein concludes that “the asymmetry mentioned in the Introduction … disappears.” Making asymmetry disappear has proved to be one of Einstein's many significant moves in his annus mirabilis of 1905. This elimination of asymmetry has led many commentators to claim that Einstein was motivated by either an aesthetic or an epistemic argument which gives priority to symmetry over asymmetry. Following closely the development of electrodynamics in the period from 1880 to 1905 and the usage of the related terms reciprocity and symmetry, we suggest a different way of understanding Einstein's motivation and the path he took. In contrast to the received view, we argue that Einstein responded to a debate in the literature on electrodynamics and that he was concerned neither with an aesthetic nor with an epistemic argument; rather, his reasoning was physical in the best sense, and most original. We will show that by providing a new perspective on the relation between electricity and magnetism, Einstein succeeded in bringing the discussion of symmetry in electrodynamics to an end.     

History of Science through Koyré's Lenses

Alexandre Koyré was one of the most prominent historians of science of the twentieth century. The standard interpretation of Koyré is that he falls squarely within the internalist camp of historians of science—that he focuses on the history of the ideas themselves, eschewing cultural and sociological interpretations regarding the influence of ideologies and institutions on the development of science. When we read what Koyré has to say about his historical studies (and most of what others have said about them), we find him embracing and championing this Platonic view of his work. Ultimately I think this interpretation of Koyré's history of science is lopsided and in need of correction. I claim, rather, that a careful reading of Koyré's work suggests that a tension exists between internal and external methodological considerations. The external considerations stem from Koyré's commitment to the unity of human thought and the influence he admits that the ‘transscientifiques’ (philosophy, metaphysics, religion) have on the development of science. I suggest in conclusion then, that if we are to put a philosophical label on his work, rather than ‘Platonist’, as has been the custom, ‘Hegelian’ makes a better fit.     

The evidential significance of thought experiment in science

The most promising way to regard thought experiment is as a species of experiment, alongside concrete experiment. Of the authors who take this view, many portray thought experiment as possessing evidential significance intrinsically. In contrast, concrete experiment is nowadays most convincingly portrayed as acquiring evidential significance in a particular area of science at a particular time in consequence of the persuasive efforts of scientists. I argue that the claim that thought experiment possesses evidential significance intrinsically is contradicted by the history of science. Thought experiment, like concrete experiment, has evidential significance only where particular assumptions—such as the Galilean doctrine of phenomena—are taken to hold; under alternative premises, in themselves equally defensible, thought experiment is evidentially inert.     

Laws of nature and natural laws

The relationship between conceptions of law and conceptions of nature is a complex one, and proceeds on what appear to be two distinct fronts. On the one hand, we frequently talk of nature as being lawlike or as obeying laws. On the other hand there are schools of philosophy that seek to justify ethics generally, or legal theory specifically, in conceptions of nature. Questions about the historical origins and development of claims that nature is lawlike are generally treated as entirely distinct from the development of ethical natural law theories. By looking at the many intersections of law and nature in antiquity, this paper shows that such a sharp distinction is overly simplistic, and often relies crucially on the imposition of an artificial and anachronistic suppression of the role of gods or divinity in the worlds of ancient natural philosophy. Furthermore, by tightening up the terms of the debate, we see that the common claim that a conception of ‘laws of nature’ only emerges in the Scientific Revolution is built on a superficial reading of the ancient evidence.     

Incommensurabilities in the work of Thomas Kuhn

I distinguish between two ways in which Kuhn employs the concept of incommensurability based on for whom it presents a problem. First, I argue that Kuhn’s early work focuses on the comparison and underdetermination problems scientists encounter during revolutionary periods (actors’ incommensurability) whilst his later work focuses on the translation and interpretation problems analysts face when they engage in the representation of science from earlier periods (analysts’ incommensurability). Secondly, I offer a new interpretation of actors’ incommensurability. I challenge Kuhn’s account of incommensurability which is based on the compartmentalisation of the problems of both underdetermination and non-additivity to revolutionary periods. Through employing a finitist perspective, I demonstrate that in principle these are also problems scientists face during normal science. I argue that the reason why in certain circumstances scientists have little difficulty in concurring over their judgements of scientific findings and claims while in others they disagree needs to be explained sociologically rather than by reference to underdetermination or non-additivity. Thirdly, I claim that disagreements between scientists should not be couched in terms of translation or linguistic problems (aspects of analysts’ incommensurability), but should be understood as arising out of scientists’ differing judgments about how to take scientific inquiry further.     

Against defaultism and towards localism in the contingency/inevitability conversation: Or,why we should shut up about putting-up

Philosophers and historians of science have for some time now debated whether the results of current science are ‘contingent’ or ‘inevitable’. Scholars have noted that inevitabilism often enjoys the status of a presumptive default position. Consequently, contingentists are, from the outset, lumbered with the burden of proof. This is evident in the case of the inevitabilist demand that the contingentist “put up or shut up” (PUSU). This paper adds to the existing case which says that inevitabilism's default-status is unjustified. However, whilst some have suggested that contingentism should replace inevitabilism as the default position, I argue that the contingency/inevitability (C/I) conversation should proceed sans default. This move is motivated largely by my claim that the C/I issue is best conceived as a ‘local’, rather than a global or universal one. The main problem with taking inevitabilism or contingentism as the default is the globalist nature of such a tack. Whilst localism is arguably an emergent reality of the growing C/I literature, its implications have not been fully realised. I suggest that fully and explicitly embracing localism, including the closely related move of doing away with defaults, represents the most promising way forward for the C/I conversation. In addition, I will show how these moves entail that we stop worrying about the inevitabilist PUSU demand, or more bluntly, that we shut up about putting-up.