American Scientist

Quantum Philosophy: Understanding and Interpreting Contemporary Science. Roland Omnès. Arturo Sangalli, trans. 296 pp. Princeton University Press, 1999. $29.95.

The line separating physics from philosophy, like the one between the quantum world and the classical, is often blurred. Roland Omn?s, a distinguished French physicist whose work has centered on the interpretation of quantum mechanics, affirms the connections between the two fields in his latest popular volume, which draws on his own work but places it in a much broader historical and intellectual context.

Omnès believes there is a crisis in epistemology—the philosophy of knowledge—brought on by developments in modern physics. Although his primary emphasis is on quantum mechanics, he also intends his remarks to accommodate general and special relativity. Indeed, the book's scope is even grander, for Omnès takes as his starting point the philosophy, mathematics, logic and science (if it can be called that) of ancient Greece. The book traces, from antiquity to the present, the histories of epistemology, mathematics, logic and science.

Omnès's goal is to show that from its initial grounding in everyday experience —what he refers to alternatively as "common sense" and "intuition"—science has become increasingly "formal." According to Omnès, science has become so formalized that it is incompatible with common sense and inexpressible in everyday language. Furthermore, because science is as close as we have yet come to direct contact with Reality (Omnès uses a capital "R"), the fact that our everyday experience is incompatible with it threatens the philosophical foundations of our understanding of the world.

Omnès not only diagnoses this malady and traces its etiology over 2,000 years. He also prescribes a cure: a revolutionary new epistemology—grounded in work done by him and others—that he believes turns the old epistemology on its head and rescues everyday experience from the maw of the quantum beast.

This is a project of epic proportions, and it begins with the intrepid physicist-turned-philosopher cast as classical hero, arriving in Hades to receive the collected wisdom of his adopted Greek forebears and shock them with his contemporary knowledge. This prelude and other passages scattered throughout the book demonstrate Omnès's creative flair and delight in language. The author has also read widely in philosophy, the history of ideas and the history of science.

Unfortunately, despite Omnès's valiant efforts, this book is flawed.

Omn?s is of course right to observe that the study of nature has become increasingly dependent upon specialized mathematical tools, certainly since Newton's Principia and perhaps earlier still. These tools are often far removed from the everyday experience of most of the world's inhabitants—only a tiny fraction of whom know anything about calculus and still fewer of whom can manipulate Schrödinger's equation. But in itself, this does not herald a crisis—after all, few people know how to fly an airplane, but that does not induce metaphysical dread in anyone.

The crux of Omnès's argument lies in his claim that modern physics is inherently counterintuitive—that it defies any attempt to understand it using "common sense" or normal, everyday experience. On the face of it this seems plausible—few everyday experiences confront us with spacetime curvature, Heisenberg's uncertainty principle or quantum effects that apparently have no cause.

Now, because Omnès also believes that modern theoretical physics should be the basis of all our knowledge, he thinks its apparent disagreement with everyday experience means we are in danger of losing our grip on the world. Physics undermines the philosophy, intuitions and even the logic based on everyday experience that we have painstakingly developed. To be valid, a theory of knowledge must be compatible with modern physics. In the latter half of the book, Omnès "saves" much of our everyday world.

Given the book's scope, it could be criticized on many different fronts. The author himself admits that he will be forced to play fast and loose with the details to make everything fit. In depicting Newton, for example, as the pinnacle of "common sense" physics, Omnès minimizes the revolutionary nature of Sir Isaac's work. Without a careful examination of contemporary thought, it is inappropriate to make assumptions about what was or was not "commonsensical" at the time. When we cast back as far as Omnès does, we must remember that, for most, inertial motion was counterintuitive, God was immanent in all things everywhere and countless angels could dance on the head of a pin. Common sense is not static.

Moreover, it is not obvious to me—and Omnès makes no serious effort to support his claim—that the oddities of modern physics are as foreign to natural language as he suggests. By venturing beyond mathematical formalisms many physicists deepen their appreciation of their theories and gain new insights. Indeed, without some everyday language, the formalism would be devoid of meaning. It is the interpenetration of the formalism with our everyday intuitions that makes the theories so productive and powerful. Here, it is perhaps telling that reading Quantum Philosophy did little to improve my understanding of the quantum world.

But suppose we grant Omnès his claims about common sense and the formalism. Even then, his idea that quantum mechanics, with the help of "decoherence" and "consistent histories," can somehow rescue everyday experience is curious. For everyday experience was never really threatened. Rather, it is quantum mechanics that has been saved, by additions like decoherence, from the embarrassment of Schrödinger's famous cat. If there were no plausible way to get from weird quantum phenomena to the macroscopic world, then most people would be inclined to think that the theory, not our experience, was due for review. The quantum menace may be strong, but in epistemology at least, everyday experience still reigns.—Daniel B. Radov, Brookline, Massachusetts