And when pain is not conveying new information, we want it to go away because pain often gets badly in the way of our goals. I find that it's extremely difficult to think clearly whilst in even mild to moderate pain, and it's also difficult to get motivated to think about or do anything, because it's hard to have any goal except "remove the pain".
Obviously, this is adaptive; a lot of the time, if you're in pain, you need to be doing whatever is necessary to get rid of the pain, or you'll meet the fate of the CIPA patients. But there are lots of situations where once the pain has conveyed its information, it's no longer serving that purpose, and yet you're still being distracted from your other goals.
I find migraines very curious as an example of pain. It's not at all clear to me what information the pain of a migraine conveys or how this information can be used, and it is certainly a dehabilitating pain that prevents you from pursuing goals other than "get rid of the migraine" -- or, as usually appears to be the only option (with a sample size of 1 here: my mother suffers from them -- so this is not data!), "wait for the migraine to stop".
Some time ago, I came across the All Souls College philosophy fellowship exam. It's interesting reading throughout, but one question in particular brought me up short when I read it.
What, if anything, is bad about pain?
The fact that I couldn't answer this immediately was fairly disturbing. Approaching it from the opposite angle was much simpler. It is in fact trivially easy to say what is good about pain. To do so, all you need to do is look at the people who are born without the ability to feel it: CIPA patients. You wouldn't want your kid saddled with this condition, unless for some reason you'd find it welcome for the child to die (painlessly) before the age of three, and if that fate were escaped, to spend a lifetime massively inconvenienced, disabled, and endangered by undetected and untreated injuries and illnesses great and small.
But... what, if anything, is bad about pain?
I don't enjoy it, to be sure, but I also don't enjoy soda or warm weather or chess or the sound of vacuum cleaners, and it seems that it would be a different thing entirely to claim that these things are bad. Most people don't enjoy pain, but most people also don't enjoy lutefisk or rock climbing or musical theater or having sex with a member of the same sex, and it seems like a different claim to hold that lutefisk and rock climbing and musical theater and gay sex are bad. And it's just not the case that all people don't enjoy pain, so that's an immediate dead end.
So... what, if anything, is bad about pain?
Let's go back to the CIPA patients. I suggested that they indicate what's good about pain by showing us what happens to people without any: failure to detect and respond to injury and illness leads to exacerbation of their effects, up to and including untimely death. What's bad about those things? If we're doubting the badness of pain, we may as well doubt the badness of other stuff we don't like and try to avoid, like death. With death, there are some readier answers: you could call it a tragic loss of a just-plain-inherently-valuable individual, but if you don't like that answer (and many people don't seem to), you can point to the grief of the loved ones (conveniently ignoring that not everybody has loved ones) which is... um... pain. Whoops. Well, you could try making it about the end of the productive contribution to society, on the assumption that the dead person did something useful (and conveniently ignore why we tend not to be huge fans of death even when it happens to unproductive persons). Maybe we've just lost an anesthesiologist, who, um.... relieves pain.
And... what, if anything, is bad about pain?
Your standard-issue utilitarianism is, among other things, "hedonic". That means it includes among its tenets hedonism, which is the idea that pleasure is good and pain is bad, end of story. Lots of pleasure is better than a little and lots of pain is worse than a little and you can give these things units and do arithmetic to them to figure out how good or bad something is and then wag your finger or supply accolades to whoever is responsible for that thing. Since hedonists are just as entitled as anyone to their primitive notions, that's fine, but it's not much help to our question. "It is a primitive notion of my theory" is the adult equivalent of "it just is, that's all, your question is stupid!" (I don't claim that this is never an appropriate answer. Some questions are pretty stupid. But I don't think that one of them is...)
...what, if anything, is bad about pain?