The many facets of Everett’s many worlds

Abstract

The 50th anniversary of Everett’s 1957 paper has brought in its wake the publication of a number of important books on Everett’s life, work and theory. This book provides arguably the most vivid and comprehensive treatment of both state-of-theart developments within and criticism of the Everett interpretation (hence the question mark in the title!). By ‘vivid’ I mean a display of argument and eloquence in papers and discussions that at times makes the book literally difficult to put down. The papers were originally given at the two main conferences that marked the Everett anniversary, at the University of Oxford and at the Perimeter Institute for Theoretical Physics (Waterloo, Ontario). The end result, published in 2010, is a wonderful achievement by the four editors, Simon Saunders, Jonathan Barrett, Adrian Kent and David Wallace, who have managed to combine a vast breadth of diverging views (including their own) into a volume that is a must for anyone interested in the Everett theory. Chapter 1 is a masterly introduction by Simon Saunders, almost 50 pages long, in which he explains and comments on the material in the book. This introduction is both detailed enough to be a really useful guide to the rest of the book and very even-handed in its treatment of contrasting positions. Part I (Chapters 2–4, by David Wallace, Jim Hartle and Jonathan Halliwell) is devoted to discussing the theory of decoherence and its role in modern-day Everett theory. Indeed, it is only with the advent of decoherence—specifically in its ability to create temporally stable structures at the level of components of the wavefunction—that the problem of the ‘preferred basis’ in Everett has achieved a solution commanding a broad consensus. Wallace’s chapter is already a classic, and arguably the place to look if one wants to understand the modern-day approach to the ontology of the Everett theory, which