This introduction to this handbook begins with the “big picture” questions about the relationship between morality and criminalization, in terms of both whether the law should reflect morality and how we should deal with uncertainty about what morality requires. From here, it turns to the wide-ranging criminalization questions presented by many of the entries, and it juxtaposes top-down and bottom-up strategies. It then draws connections between criminalization questions. Next, the introduction turns to the notions of responsible agency upon which just punishment depends. The questions of who counts as a legal person for punishment, when can a person be held responsible, and how particular features of a person’s psychology or circumstances affect just punishment are considered. Finally, the chapter concludes by examining punishment and the role of the state, asking about the mode and amount of punishment, as well as the justness of the state’s imposition of punishment.