What are prisons for?

We need to begin by asking what people are sent to prison *for*.  Unless it’s a whole-life sentence (which might better be called an ‘until death’ sentence), they are going to come out again, so the aim must surely be to persuade and enable them to change their behaviour.  The next question is, Do they have to be locked up for that?  If not, a community programme is more likely to work, doesn’t disrupt their lives so much, doesn’t cost so much.  What happened to Day Training Centres?  If the ‘public’ (or what the media and politicians assume to be the public) requires the offender to be held accountable, that can be done through reparation, more constructively than by punishment (but it shouldn’t be punishment dressed up as reparation).  It might be called the ‘Berlusconi substitution method’!
Punishment merely for the sake of inflicting pain doesn’t work and should be removed from the vocabulary. If it is felt that the seriousness of the offence must be quantified, it can be arbitrarily converted into a period of time (a prison sentence), but it can be suspended unless there is good reason for custody.  As for proportionality, if sentences are proportional now, they would still be proportional if they were all reduced by a third or a half.
No new imprisonable offences should be created unless accompanied by research evidence that they have a greater prospect of reducing than a community sentence.
A prison which cannot provide 35 hours a week of purposeful activity should be considered full and should accept no more prisoners.