For many years I have been eagerly awaiting the second edition of Neil Ashcroft and David Mermin’s Solid State Physics (Holt, Rinehart, and Winston, 1976). It is undoubtedly one of the best physics books ever written, but it is not aging well: An insensitive community keeps advancing the field with little respect for its prophets. However, after learning in Physics Today (July 2012, page 8, and Mermin’s response to letters, December 2012, page 12) that Mermin has become a QBist, I am afraid the sharp explanations in the first edition might become as blurred as Marcel Duchamp’s Nude Descending a Staircase (No. 2). How are we supposed to understand statements such as “Filled Bands Are Inert,” one of the book’s subheadings, from a QBist perspective? What is the Bayesian account of an exciton? And how about effective masses? Are they the second derivative of a belief?

My only hope is that Neil Ashcroft remains, if not a full-blown Realist, at least an Impressionist whose motifs can be clearly identified by our aging eyes.