Discussions of punishment and its role in modern societies often proceed as if punishment is co-extensive with the criminal justice system. Instead, I want to begin with the observation that a large part of punishment as a social institution is outside the criminal law — indeed much of it lies outside the legal system. To understand the working of punishment in our societies and what the law can do with it and about it requires that we examine the entire span of punishment, not just that part which epitomizes it in legal theory.
What is punishment? I hesitate to get into a definitional struggle on what must be well-worn turf. It seems to me that we can identify a core idea of “bad for bad” — i.e., the imposition of a harm, injury, deprivation or other bad thing on someone on the ground of the commission of some offence. The infliction of harm on the offender may be viewed as a goal (or as proximate to a goal of justice) or it may be viewed instrumentally as a means to social betterment, through rehabilitation, incapacitation, deterrence, reassurance, and so forth. Thus, the harm may be thought to redound to the offender's ultimate benefit or that of the society.