They don't work. And they're undeniably inhumane.
Prison is just about the most astonishingly stupid and inhuman way to punish crime. It is inexplicable that it is the main crime punishment tool we use.
Typically, the answer I get when I say this (which is often) is, "What's your alternative?" The alternatives are plentiful, and easy, and all better. But, first, let me dwell a little bit on why prison is so awful.
Prison is an incredibly stupid way to fight crime because, as is well known, it is the enemy of rehabilitation. In prison, criminal gangs flourish. This means prison becomes a graduate school for crime, a facility for turning mediocre criminals into hardened ones. More generally, who thinks locking people in places where they are fed and housed and boxed up and surrounded only by other dysfunctional people is going to turn them into productive members of society? The idea would be laughable if it wasn't part of the status quo. Prison, by its very design, breeds crime and social dysfunction.
And of course, it is impossible to talk about prison without talking about the prison rape epidemic. Can there be anything more abject than a society whose police-procedural TV shows include prison rape jokes — and nobody is outraged? Everyone knows that it goes on. Everybody knows that it's endemic. Lock up a bunch of men in tight quarters, without access to females. Many of the men are violent, over-testosteroned, and dysfunctional. What will happen? And we joke about it. On those grounds alone, the entire system deserves to be scrapped.
Maybe these problems are just from lack of reform? Maybe we just need to fund prisons more, to make the way they work better, to set up more rehabilitation programs. Sorry, that won't work. Prison doesn't suck because of historical accident. It sucks because of structural political reasons. In a democracy, an interest group gets attention and funding from the government in proportion to its numerical size and public sympathy level. The one group that will never be big enough, and certainly never popular enough, to get good treatment are prisoners. Because of the way the political system works, prisoners will never be able to get the political capital to get the reforms that might (might!) in theory make prisons not awful. We all live in Omelas.
Prisons are also contrary to the values of liberty that any civilized society ought to aspire to. As the French writer Michel Foucault argued in his landmark essay Discipline and Punish, prison is a historical oddity that arose as a result of the modern state's increasing ability and eagerness to control more and more of its citizens' lives. Well-meaning modernist reformists believed the way to set the crooked timber of man straight was through institutions that would, well, discipline and punish — schools, military barracks, prisons. It's no coincidence that the celebrated progressive Enlightenment thinker Jeremy Bentham is also the author of the Panopticon concept, one of the creepiest ideas in all history.
Prison has to go.
The comeback is inevitable: "Then what's your alternative, smart guy?"
The alternatives are actually countless, and all better. But it all depends on the kind of crime we're talking about.
For petty crime, the obvious answer is community service. It's real punishment, without the inhumane and crime-breeding drawbacks of prison. The work of community service should be geared toward reparation: For example, if you've been caught doing graffiti, you should clean graffiti; if you've been driving drunk, you should embalm corpses of people who died in car accidents. And if all fails, there is always the lash or the cane — easy, quick, much less destructive.
For more serious crimes, ankle bracelets. Did you kill someone in a fit of passion or drunk rage? Then instead of spending three years in prison, you should spend six years working minimum wage in a tedious job, your wages garnished, stuck at home with no internet or TV, with only a single night out allowed once in a while. That is real punishment — but punishment that does not have unacceptable moral costs.
As for the very serious crimes — well, I used to think the awfulness of prison was reason to support the death penalty. Now, I tend to think that prison might be acceptable for a very small percentage of crimes. If we have five percent the number of prisoners we currently have, I would be very happy.
In any case, the point should be clear: We can abolish prison — and we must.