DETERRENCE
A common justification of punishment is that it discourages law breaking: both by the individual who is punished, and by others who are aware that the punishment has taken place and will be meted out to them if they break the law. If you know that you are likely to end up in prison, so the argument goes, you will be less likely to choose a career as a burglar than you would if you thought you could get away without punishment. This justifies punishing even those who will not be reformed by the punishment: it is more important that punishment is seen to be the result of crime than that the individual concerned is changed. This sort of justification focuses exclusively on the consequences of punishment. The suffering of those who lose their liberty is outweighed by the benefits to society.