<p>Most people think that the state may incarcerate those who commit serious crimes. Most also think that a criminal justice system characterized by mass incarceration is unjust. Yet a state could bring about mass incarceration while only incarcerating those who commit serious crimes. In response to this puzzle, this paper offers a framework to explain how mass incarceration can be unjust even if each individual punishment that makes it up is independently justifiable. It argues that resolving this puzzle requires adopting a holistic approach to criminal law focusing on its relationship to the broader political order rather than narrowly on the moral quality of individual punishments. This approach reveals how mass incarceration is presumptively in tension with the state’s claim to legitimate public authority. In all but exceptional circumstances, mass incarceration involves the state using its power to punish in ways that are inconsistent with the public purposes that justify and constrain that power.</p>