Addiction may or may not be a highly prevalent condition, but the concept of addiction is undeniably ubiquitous. From the people who cheerfully and publicly announce their addiction to coffee, or chocolate, or shopping, to those who ruefully and perhaps only in very special settings admit their addiction to alcohol or drugs, ‘‘addiction” is an oft-invoked explanatory frame for the presentation and characterization of individual behavior. Lately, it has even been applied to the behavior of super-personal entities, as in America’s ‘‘addiction” to oil. Although the ubiquity of the concept is surely a sign of its usefulness, it also gives one pause; can a term of such broad application really have precise meaning (compare the word ‘‘thing”)? And if not—if there is nothing that all the ‘‘addicted” entities above have in common—then why is the concept so apparently useful, and what is it useful for? Such questions may seem tailor made for Ivory Tower semantic analysis, but in fact the matter is much more urgent than that. For we live in a world where involuntary commitments and other coercive measures are sometimes considered justified in the course of dealing with addicted persons. Why is this so? What could be wrong with addicted persons that would justify such treatment? And why is the word extended to apply to persons for whom such treatment would presumably not be justified? These are some of the several questions asked by the authors of Midbrain Mutiny, and they have not just scientific, but also political and philosophical motivations for wanting to answer them. So what is an addict? One possible definition—one that would seem to accord with the widespread use of the term—is an agent with abnormal preferences, in the sense that the addict is willing to pay far more, and to pay for far higher quantities of a good than is the average consumer. Here we should think not just of the novelist maniacally devoted to the twin pleasures of writing and alcohol, but also of the late Steve Irwin ‘‘addicted” to contact with dangerous animals, or of the infinitely more prosaic CEO who devotes all of her time to work...