Laws and Symmetry

411 Pages·1990·11.089 MB·English

by  Bas van Fraassen

Laws and Symmetry
Bas C. van Fraassen
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PREFACE
I
The idea that there are laws of nature is by no means the sole
property of philosophers. That this idea is the key to what science
is, often appears as self-evident in popular thought: in The History
of Landscape Painting, John Constable writes ‘Painting is a science’
and he adds, unconscious of any leap in thought, ’and should be
pursued as an inquiry into the laws of nature.’ That these laws
constitute also walls of impossibility that border the course of
events, is a constant preoccupation of Dostoevsky’s narrator in
Notes from Underground: ‘all the same’, he says, ‘the laws of nature
have mistreated me constantly, more than anything else in my life’.
But the idea that there are such laws has also played a major
role in philosophy concerned with science. We find this idea perhaps
most prominently in the philosopher-scientists of the seventeenth
century, but it survived in ours even the logical positivists’
radical rejection of history. Reichenbach, Hempel, and Goodman
themselves invoked laws to shed light on issues prominently-
associated with their names. Their invocation was perhaps critical
and tentative, but it seeped into other areas of philosophy as
certainty. When moral philosophers discuss free will, for example,
should they not be allowed to lean on such certainties as philosophy
of science has established concerning cause, necessity, coun-
terfactuals, and nomological explanation? And similarly, given
those supposed certainties, isn’t it quite proper too for philosophy
of mind to approach uncritically the question whether there arc
psycho-physical laws?
In the first part of this book I shall argue that no philosophical
account of laws of nature does or can succeed. In the second 1
shall rebut the argument that we must believe in them nevertheless.
Now if there are laws of nature we must approach science in one
way, but if there arc no laws, we are freed to leave behind a whole
range of traditional problems. I make a proposal for how to do
philosophy of science, and devote the third and fourth part to
contributions to the semantic approach (as Frederick Suppe baptized
it) which I advocate. The emphasis will be on symmetry, as a key
to theory, though not in the sense that law’s were.
This book was originally twice as long. When a general approach
viii Preface
is announced and advocated, it remains hand-waving except to the
extent that it is implemented. Accordingly, the now missing part
was devoted to a detailed study of the structure and interpretation
of quantum mechanics. It will appear separately, as Quantum
Mechanics: An Empiricist View.
My colleagues in philosophy of science may be a little surprised
by Part I. for the accounts of law taken up belong to the area of
metaphysics which they generally ignore. They are of course free
to ignore that part and turn to the chapters on inference to
the best explanation, theories, symmetry, classical physics, and
probability. I too lack sympathy for metaphysics, though not in
general: only for pre-Kantian metaphysics—and then only if
practised after Kant. I have tried to ensure nevertheless that none
of my arguments rests on this rejection; otherwise my critique
would not be very effective. Those who don’t care to engage the
metaphysicians on their own ground, I would like to urge at least
this: do not rely on such concept as law without inquiring whether
there is anything that could play the required role. For that is similar
to other philosophers relying unquestioningly - on fifty-year-old
philosophy of science.
There are many people and institutions I want to thank. The
original manuscript was written during a sabbatical leave (1986/7)
supported by Princeton University and the National Science
Foundation. Specific debts are acknowledged in many sections, but
I wish to thank Ernan McMullen, David Lewis, Storrs McCall,
Wesley Salmon, Michael Tooley, and Richard Foley for special
help with Part I. For Part II I want to acknowledge the help and
insights received from Gilbert Harman, Richard Jeffrey, and Brian
Skyrms. Elisabeth Lloyd helped me to see new possibilities in the
semantic approach to theories, and R. I. G. Hughes in the many
uses of symmetry. Discussions with Brian Skyrms, Maria-Carla
Galavotti, and Nancy Cartwright helped with causality, while Roger
Cooke helped with the intricacies of both classical mechanics and
subjective probability. Joint work with R. I. G. Hughes appears in
the last chapter. Perhaps needless to say, it was my valued teacher
Wilfred Sellars and my eventual colleague Gilbert.Harman who
started me on the subject of inference to the best explanation, a
number of years ago. Margot Livesey suggested a good deal of
stylistic improvement in the first three chapters and I hope this had
its effect on the later ones as well.
Preface
IX
Anne Marie DeMeo typed endless drafts of this material over a
period of about three years, and kept my practical life functioning
even while I travelled; she deserves special thanks.
Finally, I want to acknowledge with some nostalgia the places
where I wrote the draft during that initial year: Vancouver. Victoria
(BC), Montreal, Notre Dame, Bologna, Assisi, Rome, Jerusalem,
Tiberias, Cambridge (Mass.), Cleveland, and London.

SUMMARY TABLE OF CONTENTS
1. Introduction i
PART I. ARE THERE LAWS OF NATURE? 15
2. What Are Laws of Nature? 17
3. Ideal Science: David Lewis’s Account of Laws 40
4. Necessity, Worlds, and Chance 65
5. Universals: Laws Grounded in Nature 94
PART II. BELIEF AS RATIONAL BUT LAWLESS 129
6. Inference to the Best Explanation: Salvation by
Laws? 131
7. Towards a New Epistemology 151
8. What If There Are No Laws? A Manifesto 183
PART III. SYMMETRY AS GUIDE TO THEORY 215
9. Introduction to the Semantic Approach 217
10. Symmetry Arguments in Science and Metaphysics 233
11. Symmetries Guiding Modern Science 262
PART IV. SYMMETRY AND THE ILLUSION
OF LOGICAL PROBABILITY 291
12. Indifference: The Symmetries of Probability 293
13. Symmetries of Probability Kinematics 318
INDEX 387
CONTENTS
1. Introduction 1
1. The need for global constraints 2
2. The secular, global, and axiomatic method 5
3. The end of metaphysics? 7
4. The birth of symmetry 10
15
PART I. ARE THERE LAWS OF NATURE?
2. What Are Laws of Nature? 17
1. The importance of laws 17
2. Peirce on scholastic realism 19
3. A twentieth-century example: Davidson 23
4. Criteria of adequacy for accounts of laws 25
5. Philosophical accounts: the two main problems 38
3. Ideal Science: David Lewis’s Account of Laws 40
1. The definition of law 40
2. The definition of necessity 43
3. Laws related to necessity 45
4. Do Lewis’s laws explain? 48
5. Lewis’s anti-nominalism 51
6. Laws related to the pursuit of science 55
7. A parable 59
8. Conclusion: deceptive success 62
4. Necessity, Worlds, and Chance 65
1. Are there other possible worlds? 65
2. Laws related to worlds 68
3. The identification problem 72
4. Time and the branching universe 74
5. Probability: laws and objective chance 78
6. The fundamental question about chance 81
7. Possible worlds and explanation 86
8. Relation to science: Pandora’s box 88
9. The perils of a reified model 90