Before I thank the many people who have contributed to this book, a few apologies and explanations are in order. Although I spend my days punishing people, I am no expert in the science of punishment. Amateurism is, unfortunately, part of this interdisciplinary territory. Whether you prefer a scientist stomping around in law or a lawyer in the china shop of science may be a matter of taste and perspective. I just hope the chasm I leave between the law and the other disciplines I invade is not so great that I cannot be saved by helping hands from the other side. Some of my descriptions of natural selection and neuroscience may sound naive or even flat out wrong to science-savvy readers. No doubt there are many examples of both naivet´e and error. But other times missing the mark has been quite intentional, when I’ve decided to sacrifice scientific precision on the altar of readability. Examples include phrases that seem to suggest evolution is goal-oriented, including the very first sentence in the Introduction (“Evolution built us to punish cheaters”). I know that natural selection proceeds by chance, driven by random mutations and the ineluctable fact that genes will tend to be selected for whenever they give their carriers a fitness advantage in a particular environment. A special apology goes to my biologist friend Tim Goldsmith, who schooled me early on in our joint writing efforts never to use the words “urges” or “instincts” to describe behavioral predispositions. But until Tim or someone else comes up with words substantially less clunky than “behavioral predispositions,” “urges” and “instincts” will just have to do.