Nancy Cartwright

How the laws of physics lie

Most scientists are satisfied if the laws they use agree reasonably well with experiments, but philosophers look at the trickier questions of whether those laws are true in any sense. Nancy Cartwright takes the intruiging position that the theoretical models which are used in physics describe something real, but the fundamental laws which supposedly underlie those models do not. The book is aimed at philosophers of science, but it has plenty of concrete examples and so will also be of interest to scientists who want to look deeper into what underlies their subject, especially chapters 5 on phenomological laws and chapter 9 on the measurement problem of quantum theory.

The book is a collection of essays written by the author at different times, and I have to say that this reduced its appeal to me. I would have preferred a more straightforward development of the argument as the book progressed. Also I didn't find Cartwright's argument particularly convincing. She notes that physicists may use several different, sometimes contradictory, models in describing the same phenomenon. I would have said that this points to their being a more realistic underlying theory rather than the opposite. For instance in the final chapter Cartwright suggests that the quantum measurement problem might be overcome by considering what quantum statistical mechanics says about a system, rather than separating unitary evolution and non-unitary collapse. But this seems to be replacing two conflicting accounts with one more fundamental one, which goes against the main claim of the book.

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Paperback 232 pages
ISBN: 0198247044
Salesrank: 782246
Weight:0.7 lbs

Published: 1983 Oxford University Press, USA

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Paperback 232 pages
ISBN: 0198247044
Salesrank: 393614
Weight:0.7 lbs

Published: 1983 OUP Oxford

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Paperback 232 pages
ISBN: 0198247044
Salesrank: 363764
Weight:0.7 lbs

Published: 1983 Oxford University Press

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Product Description
In this sequence of philosophical essays about natural science, the author argues that fundamental explanatory laws, the deepest and most admired successes of modern physics, do not in fact describe regularities that exist in nature. Cartwright draws from many real-life examples to propound a novel distinction: that theoretical entities, and the complex and localized laws that describe them, can be interpreted realistically, but the simple unifying laws of basic theory cannot.

Product Description

In this sequence of philosophical essays about natural science, the author argues that fundamental explanatory laws, the deepest and most admired successes of modern physics, do not in fact describe regularities that exist in nature. Cartwright draws from many real-life examples to propound a novel distinction: that theoretical entities, and the complex and localized laws that describe them, can be interpreted realistically, but the simple unifying laws of basic theory cannot.

Reynart's review misstates the issues ****
Actually 4+ stars. The author -- a trained mathematical physicist -- isn't saying physics equations aren't "useful." She argues that they're generally not "true" in the ordinary sense that "grass is green" is true. Indeed, the "law of gravity" is a great example: No two bodies REALLY interact SOLELY in accordance with the "law of gravity." In the real world, electromagnetic forces, inertia, gravitation from other bodies, and a host of other forces are at play -- and you must "correct" for those other forces, Luc, if you want to land safely on Mars. So in what sense does "gravity" describe something that really happens? "Gravity," the author would argue, is better understood as a feature of a mental "model" that we build by imagining a world in which gravity is the ONLY force. The same is true of other "fundamental forces" that never exist in isolation. It's also the case that physicists often use several different, incompatible mathematical models (up to 13 in one famous example!) to describe the same phenomenon, depending on exactly what they want to investigate about that phenomenon. All of the formulas are useful -- but they can't all be literally "true" in the grass-is-green sense. It gets even more interesting when we enter the world of quantum mechanics and ask whether the "collapse of the wave function" is a "true" event that "truly" occurs out in the world somewhere. (She argues that it's not. You may recognize this as the "Schroedinger's cat" problem.) You might not care about these arguments, as I do, but it's only fair to describe them accurately.

Reynart's review misstates the issues ****

Actually 4+ stars.

The author -- a trained mathematical physicist -- isn't saying physics equations aren't "useful." She argues that they're generally not "true" in the ordinary sense that "grass is green" is true.

Indeed, the "law of gravity" is a great example: No two bodies REALLY interact SOLELY in accordance with the "law of gravity." In the real world, electromagnetic forces, inertia, gravitation from other bodies, and a host of other forces are at play -- and you must "correct" for those other forces, Luc, if you want to land safely on Mars.

So in what sense does "gravity" describe something that really happens? "Gravity," the author would argue, is better understood as a feature of a mental "model" that we build by imagining a world in which gravity is the ONLY force. The same is true of other "fundamental forces" that never exist in isolation.

It's also the case that physicists often use several different, incompatible mathematical models (up to 13 in one famous example!) to describe the same phenomenon, depending on exactly what they want to investigate about that phenomenon. All of the formulas are useful -- but they can't all be literally "true" in the grass-is-green sense.

It gets even more interesting when we enter the world of quantum mechanics and ask whether the "collapse of the wave function" is a "true" event that "truly" occurs out in the world somewhere. (She argues that it's not. You may recognize this as the "Schroedinger's cat" problem.) You might not care about these arguments, as I do, but it's only fair to describe them accurately.

A terrible ratatouille *
Nancy Cartwright juggles with all sorts of terms (phenomenological, theoretical, fundamental, realism, anti-realism, appearances, observable, non-observable, ceteris paribus ...). But ultimately, why does she pretend that the laws of physics lie? She writes: 'Does this law (of universal gravitation) truly describe how bodies behave? Assuredly not.' (p. 57) Why? Because there are other forces: electromagnetism and the strong and weak radioactive force. She continues:'For bodies which are both massive and charged, the law of universal gravitation and Coulomb's law ... interact to determine the final force. But neither law by itself truly describes the final force ... These two laws are not true; worse they are not even approximately true.' (p. 57) So what is true for her? Only the behaviour of bodies: an apple falling from a tree. More, these crucial sentences are very confusing. The words 'final force' would better be replaced by 'result' (of the interaction). There is no 'new' physical force in play here. But she goes even further (sic!):' I will allow that this law (of universal gravity) is a true law, or at least one that is held true, within a given theory. But it is not a very useful law.' (p. 58) So, one of the 4 basic laws of physics is not useful. Also when mankind is bringing a satellite into orbit with a rocket? And the 3 other forces? I hope the author doesn't have a computer. Furthermore, the author believes that the wave collapse in the quantum universe doesn't 'truly' occur. Nevertheless, the decoherence theory learns us that it is almost certain that there are no existing particle waves in the whole universe. The quantum experiment with one particle in an empty space isn't realistic (although very important). In the universe, all existing particles are continuously bombarded by other particles. Don't loose your time with this one.

A terrible ratatouille *

Nancy Cartwright juggles with all sorts of terms (phenomenological, theoretical, fundamental, realism, anti-realism, appearances, observable, non-observable, ceteris paribus ...).
But ultimately, why does she pretend that the laws of physics lie? She writes: 'Does this law (of universal gravitation) truly describe how bodies behave? Assuredly not.' (p. 57)
Why? Because there are other forces: electromagnetism and the strong and weak radioactive force.

She continues:'For bodies which are both massive and charged, the law of universal gravitation and Coulomb's law ... interact to determine the final force. But neither law by itself truly describes the final force ... These two laws are not true; worse they are not even approximately true.' (p. 57)

So what is true for her? Only the behaviour of bodies: an apple falling from a tree.
More, these crucial sentences are very confusing. The words 'final force' would better be replaced by 'result' (of the interaction). There is no 'new' physical force in play here.

But she goes even further (sic!):' I will allow that this law (of universal gravity) is a true law, or at least one that is held true, within a given theory. But it is not a very useful law.' (p. 58)

So, one of the 4 basic laws of physics is not useful. Also when mankind is bringing a satellite into orbit with a rocket?
And the 3 other forces? I hope the author doesn't have a computer.

Furthermore, the author believes that the wave collapse in the quantum universe doesn't 'truly' occur. Nevertheless, the decoherence theory learns us that it is almost certain that there are no existing particle waves in the whole universe. The quantum experiment with one particle in an empty space isn't realistic (although very important). In the universe, all existing particles are continuously bombarded by other particles.

Don't loose your time with this one.

Rubbish *
Who is the audience for this book? Dumb academics in philosophy departments who think they understand physics. This book does not say anything physicists have not already known for centuries, and it says it in a moronic way.

Rubbish *

Who is the audience for this book? Dumb academics in philosophy departments who think they understand physics. This book does not say anything physicists have not already known for centuries, and it says it in a moronic way.