Pain is the ground reality that is to be explained. If you manage to explain away pain rather than explain it, you haven't actually answered the question at all. If your answer at the end is "pain is not real", this doesn't prove that pain is not real, it proves that your premises were wrong.
If you tell me "I'm in pain", are you actually in pain?
If you are sedated with a memory blocker, and are then hurt, but you don't remember it afterward, were you actually in pain? (This isn't an academic question - many medical procedures simply paralyze the patient and add a memory blocker, but don't provide much analgesia. The patient can not express pain, and does not remember it. So does the pain they felt matter?)
You want an explanation of the wrong "ground reality", you are discussing the wrong question, it's not "is pain" real.
It's all about the subjective experience of pain, and can a robot share in that? Can a person in a coma share in that? Can an animal?
> If a computer prints on the screen "I'm in pain", is it actually in pain?
Maybe. If you SMS me that you are in pain, are you in pain? "I'm in pain" is evidence of someone being in pain. But being in pain, the referent, is just being in pain. There's no additional indirection.
> If you are sedated with a memory blocker, and are then hurt, but you don't remember it afterward, were you actually in pain?
Yes.
> You want an explanation of the wrong "ground reality", you are discussing the wrong question, it's not "is pain" real.
No, this is an issue that was actually brought up.
> > maybe [...] you [...] [don't] actually feel pain
All reason is grounded in experience. If I know anything, it's the things that I experience directly. Pain is probably the most direct experience there is.
edit:
> It's all about the subjective experience of pain, and can a robot share in that? Can a person in a coma share in that? Can an animal?
Yes. No. Yes.
These are not difficult questions to answer... You're phrasing it like there's some kind of philosophical difficulty here, but I don't think there is. If you define pain as an aversive sensory experience, ie. a sensory experience that makes you wish it would stop (this definition covers disgust and discomfort as well, and I think that's valid), then it seems clear that anything that can form goals (and yes, a memory blocked sedated person can form goals, they just can't act on them) can experience pain. I think the objection to computers is just that we rely too much on our empathy to determine when something "is in pain". I think an NPC in a game that moves away from a fire is experiencing pain, even though its mind is extremely simple, just like an amoeba would when it avoids a harmful chemical. It doesn't have such a thing as a qualia of pain, maybe (I'm not convinced!) - but that's hardly necessary.
I feel we must overcome our distrust of functional descriptions. Pain is a functional pattern, and not a very complex one.
If somebody links "free will" to "determinism", they're very confused about what free will is.
There are a lot of philosophers doing genuinely useful work, but so much of the field is pre-occupied with trivial (and non-trivial) variations of the "if a tree falls in a forest, does it make a sound?" koan.
1. Non-determinism is equivalent to determinism plus extra, random input.
2. The addition of random noise does not bestow free will upon something that didn't have it without the random noise.
3. 1 and 2 imply no non-determinstic systems can possess free will if deterministic systems cannot possess free will.
4. 3 implies free will is independent of determinism.
Maybe so are you.
Dualism holds that living entities are special, and can never be replicated artificially. So your question can actually be turned into dualism vs monism (which is not a question with a settled answer).