wait what? that's an extremely unusual stance!
What do you mean separated from the whole? all the non hand parts of me are also no longer whole but I am willing to believe amputees, even multiple amputees, even people who have lost the majority of their body can feel pain if their brain is alive and mostly intact.
This is consistent with my belief that pain experiencing happens in a centralised mass of nervous tissue we call a brain.
If you don't think centralised masses of nervous tissue are needed to experience pain (required for plants to, given that no brain is something we can prove) what do you think is? Why would a patch of grass have that thing but not a blade of grass (grass lacks localised organs afterall) or my hand?
We appear to be imagining different scenarios. Imagine it is freshly amputated and is still alive, or that we amputate it and hook it up to an artificial circulatory system, or indeed my circulatory system but at a distance so nothing else is connected (curious if you think the pain chance changes in that situation).
I'm sorry, I could have been more explicit. It seemed obvious to me discussing a dead hand was silly but being the internet it's worth clarifying these things.