Both, and some other stuff. Traditionally, the justice system is supposed to have 5 recognized goals, they are: deterrence, incapacitation, rehabilitation, retribution, and restitution
deterrence is about preventing others from breaking the law (this one is not about the incarcerated individual, but about currently law-abiding citizens outside of prison)
incapacitation is about preventing harm to society by completely removing certain people from it
rehabilitation is reasonably obvious. That being said, there are traditionally considered some people who are "beyond rehabilitation". From this view, that's not ideal, but still not the end of the world, as prison in these cases has value for several of the other reasons described.
retribution is about making the victim (or victim's family) feel better by inflicting pain on the guilty. This is a combination of explicit revenge, and keeping buy-in from the local populace by making them feel like the system is just, and keeping them feeling secure/valued.
restitution is just about financial payments to make up what the victim has lost. If someone steals your car, having them buy you a new car, plus pay some amount extra for your time is generally seen as a reasonably fair solution. This one doesn't necessarily involve prison unless the defendant refuses to pay.
Also, this is a nit but deterrence is usually considered to be about both the incarcerated individual and other citizens. Deterrence against re-committing the crime is an important part of incarceration, and I don't think it reasonably fits under rehabilitation.
Yes, I would consider it part of the rehabilitation process.
> Also, this is a nit but deterrence is usually considered to be about both the incarcerated individual and other citizens.
This is fair. I was trying to draw the point that it's about people outside the prison (which the convict who may later re-offend would be when they're facing the choice to re-offend). I think I phrased this poorly/wrongly. Thanks for pointing it out.
That reason is because “penance” is, in ecclesiastical law, the earthly penalty for sin, and a “penitentiary” is a place dedicated to the experience of those consequences.
The connection to “penitence” (“the action of feeling sorry and regret for having done something wrong”) is more distant. (Also, the desire to cause penitence is more directly retribution, though it can be viewed as instrumental to rehabilitation.)
Deterrence is about preventing the offender (specific deterrence) or other people (general deterrence) from breaking the law through intimidation by making manifest the adverse consequences thereof.
Rehabilitation is about preventing the offender from committing crimes by removing/reducing/counteractinf the inclination to do so (other than by intimidation.)
Incapacitation is about preventing the offender from committing crimes by denying them capacity, to some degree or for some period.
(Restitution and retribution are not aboit preventing crime.)
In practice, the US tends to ignore the science and deterrence ans rehabilitation and not optimize for it, and marginalizes restitution in the criminal justice system, so thr criminal justice system is mostly about retribution and incapacitation.
As downtown SF is currently demonstrating, prison is designed to separate. If you let violent criminals and the mentally ill sleep on the street and steal at will, it makes life much worse for everyone else than it makes life better for them.
I think it's meant to remove.