From my basic understanding, there are three basic schools of thought for "justice:" Retaliation, rehabilitation, or preventing recurrences. Revoking a drivers license for a DUI falls under preventing recurrences. Eye for an eye is retaliation. I am rather against retaliatory "justice."
Throw "reparation" in there, too. T'me, the ideal system is one combining reparation, rehabilitation, and preventing recurrence (though note the last is largely a matter of the second, in the majority of cases).
In the case of accidental eye loss, the one inflicting it covers medical fees -- either explicitly through civil fines, or incidentally through a universal health care system the one causing the harm pays in to.
For something like a DUI wreck, the one inflicting the harm would cover any medical or property damage -- either out of pocket, or through the government covering it and the one that did the deed performing community service until the debt is paid back -- then go through rehabilitation and likely temporary or permanent license loss. Potentially blacklisted from purchasing alcohol, as well.
The trend would continue upwards. Rape, covering cost of therapy/medical one way or another -- and likely further fines to cover loss of productivity, quality of life, etc. -- extensive rehabilitation, likely means of preventing recurrence afterwards (surveillance, relocation, etc.).
Murder would be about the only potential exception, since there's not really a way to meaningfully offset the harm done by such. It would likely entail imprisonment and remaining lifetime being spent on some form of useful community service.
Overall, the way I've come to see it is sort of transactional. A crime (ideally, when the designation isn't being abused) is something that draws from the overall account you could label "Societal Good". The base purpose of justice is to offset that transaction so the net effect on the societal good account is zero, and hopefully (in an absolutely ideal scenario) adjust the situation such that the ultimate results is a net
gain. A criminal is still a member of society, and their well being part of the societal good -- a sub-account, if you will. Punishment is a withdrawal from their particular account. If it is not offset by
something -- an improvement in behavior, some form of physical reparation, etc. -- then all you have accomplished is to make the overall account shrink further. There has been no gain, and the net loss is made even greater. The
goal is to balance harm -- shift resources from the one who has caused it to those who were harmed -- and adjust the asset (the criminal, or the overall situation) such that it brings a net gain to the overall good in the future.
A punishment is only effective if its severity is equal to or outweighs the benefits of the crime comitted, so as to make comitting said crime to be unappealing and thereby preventing it.
I'd disagree here, to an extent. Part of the problem of retributive justice -- making sure the punishment exceeds the benefit of the crime -- is that it
doesn't work in many situations. Executing or imprisoning someone who commits a crime of passion does little to nothing insofar as preventing further crime of that nature. Killing off or imprisoning the criminally insane does little to nothing insofar as preventing further crime from such individuals. For a great many crimes and a great many criminals, severity of punishment is literally irrelevant -- it has no bearing on their decision making. For many (most, to my understanding) others, it's
still not a very good deterrent -- societal pressures are more effective by a huge margin. Punishment as a deterrent just isn't very good at what it sets out to do.