Hit points are an abstraction that can represent almost anything you want, from sheer superhuman toughness, to incredible luck, to flesh wounds, to simple fatigue.
But a long time ago I actually asked Gygax when I was attending Gen Con. He told me to think of it as "points until you get hit."
That's still pretty vague, but I always thought he meant 'until you take a vital hit' or something like that. Either way, it stuck with me to this day.
As I recall the AD&D DMG, that's precisely what GGG meant - until your foe lands the killing blow, hit points are an abstract, the wearing down of your stamina and defenses. Being reduced to zero hit points means your foe landed the killing blow. Before then, you get knocked about, nicked up, bruised and scratched. It's a
melee, fer crissake.
The way D&D in its multiple iterations manages the reduction of combat stamina is not perfect, but it's quick, it's easy to grok, and it's easy to build a game engine to resolve.
Gary's concept of HP as abstract is also why this...
Consider the case of an assassin with a poison dagger. Even at full hp, if the dagger hits, the target will have to save versus poison. Clearly that is not a case of a blocked attack or a mere bruise. The target must have been cut (even if it is only a scratch) in order to introduce the poison to the bloodstream (which in turn prompts the saving throw).
...makes sense, especially in the context of the many save or die poisons in AD&D.
It also is partly consistent with this...
Read the sidebar from page 197 of the PHB. I'll quote the relevant part below.
"When you drop below half your hit point maximum, you show signs of wear, such as cuts and bruises."
That right there proves that more than bruising happens at 1-49%. You also get cuts, and cuts bleed. They just don't bleed enough to threaten your life like the serious cuts that happen when a PC hits 0. It also shows that piercing and slashing damage do puncture the skin and do more than bruise PCs. Same with spells.
...but not entirely. I think somebody dropped the ball on this, and that it needs to be addressed in future printings, as it is incompatible with a target taking poison damage before being reduced to half hit points.
In other words, "you take 6 points of piercing" doesn't necessarily equate to "the goblin shoots you with an arrow for 6 points of piercing damage." The arrow doesn't have to actually puncture your skin to deal the damage. It can be abstracted as the stamina reduction of dodging out of the arrow's path. If you have some sort of physical or magical resistance to piercing damage, you could abstract that as your adamantine armor means you don't take full stamina damage from dodging - because you don't have to dodge by leaping out of the way - but the physical blow of the arrow hitting you might leave a bruise, you still flinch, and that distracts you.
As others have noted, this argume...I mean debat...I mean
discussion has been recurring for 40 years. The only workable way I've seen to make HP less abstract within the D&D umbrella of games is the old weapon vs. armor type tables of AD&D. Those were clunky, slowed the game to a crawl, and frankly still didn't capture the differences in combat damage application. Even other systems, like Rolemaster, with infinitely more realistic combat and damage mechanics, still rely on HP as abstract to a greater or lesser extent.
The trouble is HP as abstract isn't very satisfying as a story element. That's understandable, as this whole shebang developed as an expansion of tactical wargaming rules. And once anyone noticed, it was The Way We Do Things, and now it's so firmly traditional that to change it would change the flavor of D&D to its detriment. That makes resolving the discussion, as others have pointed out above, a fool's errand. All we can do is cope with it as best we can. Personally, when I DM I try to remember how each PC can conceivably take physical damage, so as to describe the HP reductions in a way which is consistent with my concept of "HP as abstract." That's as far as I can go without porting over the Rolemaster combat rules - which I have considered!
Cheers,
Bob
www.r-p-davis.com