This book is the result of the third Erasmus Ascension Symposium organized by the Praemium Erasmianum Foundation in Amsterdam. The Praemium Erasmianum is known primarily for the Erasmus Prize which, since 1958, has been awarded annually to individuals or organizations in Europe that have exceptionally distinguished themselves in the field of European culture. In addition to this activity, every two years the Foundation also organizes a symposium in the Netherlands concerning a specially chosen multi-disciplinary topic of current interest. In 1992, in conjunction with a day that was open to the public, a select group of 40 young Dutch scholars once again had the opportunity to engage in a penetrating and in-depth discussion on the chosen topic with a number of specialists during the three-day symposium.

The choice of the theme for the 1992 symposium, Physics and Our View of the World, was prompted by the great interest that exists for this topic, as is evident from the appearance of so many semi-popular publications in this field. In this way, the Foundation hoped to provide a forum for the useful exchange of views and ideas about the philosophical and religious implications of recent developments in modern physics. We thus hoped to help bridge the gap between the realms of the exact and the spiritual sciences, a division which is still so apparent in our time.

Of all the systems of thought aimed at understanding the world, what we call the scientific method stands out as the most successful. Not only has science led us to many new and unexpected discoveries about the world, it provides a powerful conceptual framework within which to organize our thinking about natural processes. Moreover, within the scientific community there is a remarkable degree of agreement about the way the world is.

In the chapters by Professors 't Hooft and Barrow we read that physics — the foundational science — may be approaching a point of culmination with a so-called Theory of Everything. We have been rightly cautioned against expecting too much from this endeavour; nevertheless, the very fact that such sweeping claims are even discussed itself attests to the power and scope of modern physical theory.

While remaining enthusiastic but sceptical about a Theory of Everything, I believe that the discussion of such a theory throws into sharp focus many of the basic assumptions that underlie the physicist's approach to the nature of reality.

In its most ambitious form, a Theory of Everything seeks to combine all physical laws and principles into a single, unified mathematical scheme, hopefully captured by a single, simple formula that you might be able to wear on your T-shirt.

Introduction

In the last three centuries physicists have come up with a surrogate for God. It is the conception of laws of Nature as universal and eternal, comprehensive without exception (omnipotent), independent of knowledge (absolute), and encompassing all possible knowledge (omniscient). In other words the structure of physical laws has all the classic metaphysical attributes of the Deity (Davies, 1992). In this light are discussed many of the perennial problems about the meaning of the Universe that have traditionally been the concern of religion: how and when the Universe began, possibly how it will end, its evidences of design, its deep and comprehensive orderliness, the beauty of the theories devised to explain it, the wonder of human capacities to penetrate its mysteries, the duty that rational beings have to pursue precise explanations of things as far as these will go.

There is no doubt that there is great fascination and excitement among the educated public about these metaphysical- and theological-sounding claims. Why? Probably for two chief reasons: first because in our secular society we have lost the depth, coherence and value that used to be given to life and the world by religion, and second because natural science has appeared to be the only decisive successful way of reaching the truth about things, and has been exploited as such by post-Enlightenment philosophy, particularly that of the Anglo-American world.

My topics are the relation between science and myth, and the possibility of empiricism as an approach to life as well as to science. But philosophy is a thoroughly historical enterprise, a dialogue that continues in the present but is always almost entirely shaped by our past. So I will devote the first half of this chapter to setting the historical stage.

Two philosophical traditions

There are two main traditions in philosophy about science and about our knowledge of nature; I'll refer to them as realist metaphysics and empiricism. Both of these can be approached more narrowly as concerning how we should understand science. But we can also think of them more broadly as concerned with making sense of the world and, at the same time, of our attempts to make sense of the world.

For the realist, science is a journey of discovery. In fact, realists think of philosophy and science as jointly trying to uncover what is really going on in nature, even ‘behind the scenes’ so to speak. And at the same time, the realist sees science as aiming at real understanding of how nature works, and why it is the way it is. The two aims, of discovering what the world is like, and understanding or making sense of it, are not automatically the same! But for realism there is no tension between them — they are happy to identify the What and the Why.

Summary

The last two decades witnessed a new breakthrough of fundamental physics in its struggle towards a better understanding of the World of the Small. This gave rise to new speculations concerning the idea that there may exist a single ultimate Law of Physics underlying all particles and forces, and therefore also everything made out of these particles held together by these forces, which could include us and the universe. Discovering this Law would be a tremendous achievement, but would not at all imply our understanding of most of its consequences. In this chapter I focus on two themes:

1. Speculations that such a fundamental Law exists and that there is a possibility that we humble human beings may in due time be able to find this Law and give a detailed and precise formulation of it — including boundary conditions and initial conditions if necessary — are far from ridiculous (Section two), in spite of lessons from the past. Our present knowledge indicates that the possibility is real (Section three).

2. Claims made by several theoretical physicists that they are coming very close towards actually realizing this hope are highly premature and naive. ‘Superstring theory’ is almost certainly not the answer. The dispute concerning the physical interpretation to be given to the formalism called ‘quantum mechanics’ will have to be continued, and it is as yet impossible to predict the vastness of the undoubtedly formidable obstacles that are still in our way (Sections four and five).

Introduction

Despite the topicality of Theories of Everything in the literature of science and its popular chronicles, they are at root a new edition of something very old indeed. If we cast our eyes over a range of ancient mythological accounts of the world we soon find that we have before us the first Theories of Everything. Their authors composed elaborate stories in which there was a place for everything and everything had its place. These were not in any modern sense scientific theories about the world, but tapestries within which the known and the unknown could be inter-woven to produce a single meaningful picture in which the authors could place themselves with a confidence born of their interpretation of the world around them. In time, as more things were discovered and added to the stories, so they became increasingly contrived and complicated. Moreover, whilst these accounts aimed at great breadth when assimilating perceived truths about the world into a single coherent whole, they were totally lacking in depth. That is, in the ability to extract more from their story than what was put into it in the first place. Modern scientific theories about the world place great emphasis upon depth — the ability to predict new things and explain phenomena not incorporated in the specification of the theory initially.

Aims of the paper

Philosophers have much extended our understanding of the foundations of spacetime physics in this century. They go on doing so. Much of this is the work of positivists and conventionalists. Friedman (1983, Introduction) tells us in his excellent book that we must learn from their mistakes if we hope to go beyond them. I will look at two of their mistakes: one is about simultaneity and the other is about the relativity of motion.

In my view, the most interesting and suggestive arguments take the old-fashioned form that the world could not possibly be as our best scientific theories say it is. One argues that physics, as the scientists hand it down to us, is conceptually awry and must be rewritten, either by amputating parts of it or by interpreting these parts as conventions, not factual claims. They are metaphysical arguments. In this century, Mach, Einstein, Reichenbach and Grünbaum have urged them. Epistemology appears in them only by ruling out concepts from a fact-stating role unless they meet some observational criterion or other.

It would be absurd to claim that this exhausts the normative role of epistemology in the philosophy of science. But I see little value in asking, about these dismembered forms of physical theory, whether they are better evidenced than the standard forms used by the practising physicist. We philosophers are not likely to choose better than they do, even if we enlarge their view of what they may choose among. Further, a main theme will be that a focus on the observationality of ideas and on parsimony of theoretical structure misled us for decades as to what spacetime theories were about.

First edition

It has been my aim in this book to revive and defend a theory generally regarded as moribund and defeated. Consequently, I owe most of my intellectual debt to those against whom I try to argue in these pages. Above all, Hans Reichenbach's brilliant Philosophy of Space and Time has been the central work I wished to challenge and my model of philosophical style. My debt to the books and papers of Adolf Grünbaum is hardly less important. I am glad indeed to take this formal opportunity to express both my admiration and my debt to these writers who are subjects of so much criticism in this book. Quite generally, indeed, I acknowledge a real debt to all those philosophers whose work it has seemed important to examine critically in these pages.

This book is the fruit of courses I have given for a number of years in the philosophy departments of the University of Sydney and of Adelaide. Among many students whom it has been an education to teach, I hope it is not invidious to mention Michael Devitt, Larry Dwyer, Clifford Hooker and Ian Hunt as particularly helpful in early stages.

The whole of the typescript was read by Dr Ian Hinckfuss and Professor J.J.C. Smart (my first teacher in philosophy). Their comments and criticism have been invaluable. Various parts of the book have been read and discussed with Robert Farrell, Bas van Fraassen, Henry Krips, Robert Nola, Hugh Montgomery and Wai Suchting. I am grateful to my colleague Dr Peter Szekeres for his patience with many queries I have put to him about General Relativity.

The essays in this part are about issues which arise within special relativity in one way or another. Each of them argues that the special theory is a more structured, ontologically richer and deeper theory than many philosophers have taken it to be. Several of the essays raise questions of methodology for the metaphysics of spacetime. All of them sustain and explore the theory that spacetime performs a unique and crucial role in explanation which earns it a secure place in our ontology.

From rather early in its development it was realized by Robb (1914) that the full metric structure of spacetime could be built on surprisingly slender foundations. Robb laid down a few axioms on a relation which he called after. This idea failed to seize general attention for a number of years. It was taken up subsequently by a number of writers, notably, for our purposes, Zeeman (1964), Hawking and Ellis (1973) and Winnie (1977). (A compact, accessible and elegant account of this may be found in Lucas and Hodgson (1990), chapter 3.) The key relation was now called causality by all these writers and is now thoroughly established in the literature under that name. This lends colour to the idea that, somehow or other, a notable reductive victory has been achieved: the geometry of spacetime has been dethroned from its status as an abstract structure within which material structures are contained. The only structure we need to be concerned with is fully physical and unpuzzling. It is causality.

A recurring theme among the essays of this part is that nothing of the kind has occurred. I must emphasise that I don't dispute the main substance of the work of Robb, Zeeman and the others.

Space and shape

Naively, we think that left and right hands differ in shape. But we just saw that there is actually no intrinsic difference of this kind between the things themselves; there can only be a difference in the way they are entered in a certain kind of space. Hands can differ if their containing space is orientable. If it is not they will all be alike however we enter them in it. We found this out by looking at the spaces defined by a paper strip from outside it. A paper cylinder is orientable, but if we cut it and twist it we can change it into the non-orientable Möbius strip. It alters what things do when they move in the space defined by the strip. This looks as if we can say that the difference in the spaces is a difference in their shapes. The shape of space is to play an explanatory role in our theory of the world. That is what we need to make some sense of. But making sense is just the problem. Can we properly speak of the shape of space?

Now it seems all very well to say that space has a shape when we can regard it as defined by a strip of paper, the surface of a ball or of an arbitrarily far extended table top. We see it from outside in a space of higher dimension and it is visibly twisted, curved or flat from that vantage point.

Introduction

Euclid's geometry is so brilliant that it has always dazzled us. It shone for centuries so brightly as to blind us to any model for an established branch of knowledge but the deductive system based on a few self-evident axioms. Thus it misled metaphysics. But that is not my theme. I want to show how it led Leibniz to some mistaken arguments in the central letters of the Leibniz–Clarke Correspondence. The letters are about quite special issues in the metaphysics of space. But they have dominated philosophy since then as our models of how epistemological arguments should decide metaphysical questions. My theme is to reveal the arguments as mistakes.

Space sets ontology one of its most acute, searching and elegant problems. To change my visual metaphor, the reason why we have not been able to see further into this subject is because a giant has been standing on our shoulders. He is Leibniz. Though the arguments in his letters are fallacious, surely he is a giant. What can make those fallacies clear to us was not available to him nor to his great opponent, Newton. But first, what is the problem space sets for ontology?

On the face of it, space has disconcerting properties. The list below is loosely phrased, and neither exclusive nor exhaustive.

Introduction

Almost everyone who has a considered opinion about what the conceptual foundations of SR (Special Relativity) might be, thinks that they lie in causality. (But see Lacey 1968, Smart 1969 and Earman 1972 for opposite opinions.) Cause is said to be the basic concept of the theory. The basic thesis (statement, postulate) of SR which makes use of this concept is said to be the Limit Principle: nothing (including causal processes) goes faster than light. This opinion about SR's foundations which I will call the standard view, is a philosophical one, not just because it is about conceptual foundations but also because many who hold it envisage the success of a programme attributed to Leibniz. It reduces the metaphysically uncomfortable ideas of space and time to the single familiar idea of physical material cause. This picture of the theory as specifying for itself how its bold new structure rests neatly on secure old foundations, as basic as can be, does much to shape our wider ideas about how people build their concepts and theories and about how these grow out of older concepts and theories.

Despite the widespread enthusiasm for it, and the careful and ingenious way it has been developed, the standard view remains doubtful. The Limit Principle is very probably not even a consequence of SR and certainly not among its basic postulates. It is uncertain which concept causality is and whether the relation is fundamental to anything. I think that the standard view is false and that is what I will try to argue.

Introduction

What physics books are apt to say about SR (Special Relativity) is not quite the same as what philosophy books are apt to say about it, as Wesley Salmon points out in his excellent Space, Time and Motion (1975, p. 113). He explains this difference reasonably enough, as due to disparate main interests which SR has for physicists as against philosophers. The former want to develop quickly an apparatus which allows the clear, deft portrayal of central principles and results in physical prediction and explanation. The latter prefer a more leisured approach to this goal so as to give scope for a deeper insight into the semantic-syntactic structure of SR. Most philosophy books say that the language of SR has various conventional elements in it, which means that the theory can have no very simple relation between its syntax and its semantics. In particular, the matter of the simultaneity of space-like separated events is settled conventionally, and this gives rise to a contrast in SR between sentences which form a factual core (Winnie 1970, p. 229; Salmon 1975, p. 117) and others which make up a periphery of non-factual sentences with a merely syntactic function. In what follows I ignore the problem of what other conventions might have a place in SR. I want to examine and reject just this idea that simultaneity is a convention, as this gives rise to the idea that we can contrast a core of factual sentences of SR with a periphery of merely conventional ones.

Wesley Salmon's thought on this central problem is certainly conventionalist. Besides its admirable clarity and precision, Salmon's work contains many valuable arguments and observations on the structure of SR.