Abstract

These two books, both by distinguished authors, are excellent. Though they are written by and for physicists, they are an invaluable resource for philosophers interested in the grand theme of how classical physical phenomena emerge from the quantum realm. Both individually and taken together, they are fine representatives of the present state of knowledge about this theme, and about many more specific topics falling under it. They are also pedagogic, though aimed at an advanced level—graduate students and beyond, in physics and mathematics. Thus, they are packed with sophisticated expositions of such topics as quantum Brownian motion, and decoherence in quantum field theory, the rigorous definition of macroscopic observables and of their evolution laws in quantum statistical physics, and the rigorous treatment of open quantum systems. So overall, they provide an invaluable overview of a large and lively research area of physics. But the books are also different in several ways. The first book, by Joos et al., has six authors, all theoretical physicists based in Germany and part of the ‘Heidelberg school’ of decoherence physics, which has grown up in the last twenty-five years under the tutelage of Heinz- Dieter Zeh. The second book is a monograph: Sewell is a British mathematical physicist, most of whose work has been in the algebraic approach to quantum statistical mechanics. Other, less obvious, differences follow on from these. By and large, the material in Decoherence is both more familiar and more accessible to philosophers of physics. And for reviewing the books for philosophers of physics, it will be a convenient strategy to spell out the three reasons for this contrast. But as we shall see, Quantum Mechanics being more difficult need not mean it is less valuable. First, decoherence processes of the kinds that Joos, et al., mostly discuss are now well-known to philosophers of quantum theory, not least through the work of the Heidelberg school itself and of the ‘Los Alamos school’ of Zurek and coauthors. Indeed, Joos’ own Chapter 3, “Decoherence through Interaction with the...