On the Exploring Pain: Research and Meaning group on Facebook, Phil Greenfield asks:
“Seeing pain as a ‘thing’ is somewhat inevitable. Pain is so immediate and unpleasant that sufferers naturally want rid of ‘it’. This has spawned a whole raft of of therapeutic models turning out technicians who would claim to be able to remove that ‘thing’ for you.
The experience of pain also has a noun assigned to it (pain) making it even more likely to be seen as a ‘thing’.
The big issue is, how can we uproot that rather persistent problem, and reframe our view of pain as being more akin to love, or grief, or anger, insofar as it has certain sensations associated with it, but that those sensations are not by any means the whole story”.
My response to Phil’s question was (edited):
As I argued in the group here and here, the word ‘pain’, like ‘nausea’, or ‘itch’, is a name of a sensation, but not in the way in which ‘table’ or ‘chair’ are names of furniture. We can point at a table and say that ‘table’ is the name of this (pointing gesture) piece of furniture, but I don’t think we can point at a sensation and say that ‘pain’ is the name of this (pointing gesture) sensation.
I think to say that ‘pain’ is the name of a sensation is to say that there are typical behavioural manifestations of pain, which support statements like ‘Bob is in pain’, and that people who self-report pain are not describing a hidden (Cartesian) object ‘in the mind’, but are signalling to others what is going on with them.
Still, we find it natural to think that pain behaviour is the external sign of a mental object private to the sufferer, which in principle is hidden from observers. In the context of pain underestimation, Kenneth Prkachin writes:
“Evaluating others’ pain is a classic case of decision-making in uncertainty. The difficulty of the task is complicated by the fact that the clinician must try to “look inside” another person. In an ideal world, the clinician would be able to use some kind of “mental dipstick” to slide inside the patient’s consciousness, capture her or his current state, and, on the basis of this reading, recommend further action.
What are the potential sources of underestimation?
A first answer to this question harkens back to the dipstick problem. Because observers do not have direct access to sufferers’ internal experiences, their judgements are reliant on sources of evidence in the sufferer’s behaviour or context. In the setting of most empirical studies, access to that evidence is limited.”
We tend to think that the sole purpose of language is to represent reality; but pain behaviour, including linguistic self-report, does not function to accurately represent a private pain ‘object’. It sounds odd to say, but pain behaviour is not caused by the pain sensation!
Pain behaviour promotes the survival of our species, and is linked with caregiving and care-solicitation; resource allocation and conservation; charity and responsibility toward other members of our big family.
Simon van Rysewyk 
Simon, another claim that is being championed around the physical therapy world posits pain as a protector of bodily tissues, and that “it” also facilitates healing after injury. The fact that no one who believed this claim when being burnt alive at the stake has survived to tell the tale tends to make me skeptical.