In a world fascinated by tales of redemption and retribution alike, it is perhaps unsurprising that the question ‘why punish?’ remains challenging to answer satisfactorily even in the 21st Century. Yet money, time and even lives continue to be sacrificed to the endeavour of responding to crime, and so it is vital that the imposition of criminal justice interventions can be defended as both justifiable and useful.By deconstructing the question ‘why punish’, Chapter 1 identifies the goal of freedom enhancement as central to criminal justice, and so proposes the concepts of justice and desistance as a route to establishing a theoretically sound foundation for those interventions. Chapters 2 and 3 analyse these two wide-ranging literatures, identifying a set of hallmarks for each. Finally, Chapter 4 seeks to bring the two foundational concepts together, highlighting the unexpected compatibility of two concepts traditionally perceived as contradictory, while seeking to reconcile their more divergent aspects. By analysing the interplay of each of the justice and desistance hallmarks, the chapter argues that legitimacy and usefulness can be achieved through a genuine collaboration between the two concepts, albeit a collaboration that would demand undeniably radical reform across the criminal justice system and wider social structures. As such, it is acknowledged that the thesis holds up an ideal, challenging the current system of highly punitive sanctions leading to high recidivism rates, rather than accepting or defending it.Ultimately the conclusion of this theoretical study shows that criminal justice interventions must rest on a basis of both legitimacy and utility, responding appropriately to the past facts of offending, and providing an evidence-based contribution to reducing incursions into freedom caused by reoffending. This thesis argues that underpinning criminal justice interventions with ideas of justice and desistance could present a route to such a system, but that in so doing a new question is raised as to the type of system that would be needed to achieve it. The final part of Chapter 4 therefore speculates that understanding criminal justice in the context of a service paradigm might be necessary in order to achieve true legitimacy and usefulness in intervention.