Ashcroft replies: Realist, and calibrated as full-blown? Given the subtleties of the notion of reality, I somehow doubt it. Impressionist? I delight in freely recorded broad-brush renditions of the observable physical world. But Marcel Duchamp’s painting comes across more as a superimposition of rather sharp images. They seem to reflect quite lucidly a progression in time of a more developed form.

Over the years many readers have remarked that the initial edition of our book should “not be touched”; it is just right in its treatments of the fundamentals. But by all means augment it with a sequel, encompassing the many advances in condensed-matter physics that have occurred over the past 38 years. The view that it should not be touched seems to have been shared by those who translated our 1976 text into French, German, and Portuguese just within the past decade.

José Menéndez’s laudatory comments about our book are generous in the extreme. David and I are both grateful, and together we hope that the aging process, of ourselves and of our textbook, will not unduly accelerate.