In case it's not clear - when I play D&D I generally don't sweat too much about hp, but when I do think about them I think of them as a measure of resilience in the face of threats to life and (sometimes) sanity. (The second conjunct is there mostly in relation to psychic damage.) Depletion of hp is the wearing down of resilience; the restoration of hp is the retoration of resilience, whether by physical healing or (more often, in my preferred version of D&D) by the restoration of morale and vigour.
One way to have greater resilience in the face of these threats is to have greater durability. Another is to have greater courage or willingness to go on. So while I agree with @Arch-Fiend that hp are an abstraction, I think I adopt a different view as to what the abstraction is concerned with.
I don't think it's all that important to debate who is right about that. If I turn from 4e to Gygax there is mention (in the DMG, pp 82, 111-12) of "the actual physical ability . . . to withstand damage", "skill in combat . . . [and] the 'sixth sense' which warns the individual of some otherwise unforeseen events" and "luck", "magical protections", "divine protection" and "the aid provided by supernatural forces". Nothing there goes as far as 4e in supporting a morale/vigour/resilience approach. The focus seems to be on skilled and/or lucky avoidance plus magical wardings that result in potentially terrible blows falling only lightly on the character.
If I can handle 4e's resilience approach, and Gygax's defness and good fortune approach, I'm sure I can cope with Arch-Fiend favouring a durability approach. I don't agree with Arch-Fiend that a durability approach does better than those other approaches in avoiding "ludonarrative dissonance" caused by damage types and CON affecting hit points. Gygax's DMG tells me that CON represents "physique, health, resistance, and fitness" (p 15) and that seems to allow for high CON aiding resilience and deftness just as it would aid durability. It's true that there's an overlap with AC, but that applies equally to durability (because wearing armour makes a person more durable). D&D has never been shy of having multiple mechanical systems overlap in respect of the details of the fiction that they pertain to.
One way to have greater resilience in the face of these threats is to have greater durability. Another is to have greater courage or willingness to go on. So while I agree with @Arch-Fiend that hp are an abstraction, I think I adopt a different view as to what the abstraction is concerned with.
I don't think it's all that important to debate who is right about that. If I turn from 4e to Gygax there is mention (in the DMG, pp 82, 111-12) of "the actual physical ability . . . to withstand damage", "skill in combat . . . [and] the 'sixth sense' which warns the individual of some otherwise unforeseen events" and "luck", "magical protections", "divine protection" and "the aid provided by supernatural forces". Nothing there goes as far as 4e in supporting a morale/vigour/resilience approach. The focus seems to be on skilled and/or lucky avoidance plus magical wardings that result in potentially terrible blows falling only lightly on the character.
If I can handle 4e's resilience approach, and Gygax's defness and good fortune approach, I'm sure I can cope with Arch-Fiend favouring a durability approach. I don't agree with Arch-Fiend that a durability approach does better than those other approaches in avoiding "ludonarrative dissonance" caused by damage types and CON affecting hit points. Gygax's DMG tells me that CON represents "physique, health, resistance, and fitness" (p 15) and that seems to allow for high CON aiding resilience and deftness just as it would aid durability. It's true that there's an overlap with AC, but that applies equally to durability (because wearing armour makes a person more durable). D&D has never been shy of having multiple mechanical systems overlap in respect of the details of the fiction that they pertain to.