It’s been about a month since I first opened the topic of hit points in D&D. Although I still haven’t had the time to get in to the meat of it, I did want to look at a little bit of history of hit points. That being said, I didn’t enter the hobby until the late ’90s, so none of my history lessons come first-hand.
In Chainmail, as near as I can tell, there was no notion of hit points; a unit was hit or not and, once hit the unit was dead. There was apparently a set of rules made to model Civil War era ironclads (as noted by Roles, Rules, and Rolls), where the structure of a ship could take so much damage before being sunk. According to the interview RR&R references, those rules were incorporated into D&D in order to ease the harshness of sudden, random death that Chainmail would have otherwise. This let D&D players act and feel like heroes.
Anecdotal evidence (the first comment, not the linked post) suggests that hit points for humans were originally set at 7, but player complaints lead to an increase. Though, it seems like OD&D had starting hit points ranging from 1 to 7 (d6+CON), and 0 hit points was dead. Then in AD&D, various hit dice were introduced based on class, with a range of 1 to 9 (depending on class and CON) for first level characters. Again, evidence suggests these numbers were historically meant to represent regular people; the average joe.
So originally (for some value of “originally”) something around 4 points of damage were enough to kill a man (on average), but a burly fighter might be able to withstand twice that. This is a rather coarse-grained system in that it can really only measure one quarter of a man’s vitality — anything less is too small to be measured. This was alleviated a little bit with the addition of “below zero” rules, where a character was incapacitated (and dying) at 0hp, but they weren’t dead until -10 — it effectively takes 14 points of damage to kill the average man and 19 to kill a burly fighter, which is a much closer ratio than 4:9. This addition makes the system a bit more granular and levels the playing field a bit (fighters are no longer taking two mortal wounds before they die). With 15 to 20 points of granularity (though, less than half of those count as “action-ready”), there’s a lot more room to address ‘lesser’ wounds, but we’re still talking about the sorts of things that are going to leave a mark and require a bit of time to recover from. A busted lip is probably not hit point damage.
Hopefully it won’t take me another month to address ‘modern’ notions of hit points (I don’t think current systems stray too far from the historic baseline, at least not at first) and the contention that hit points are incoherent, that they are explained as “luck, divine favor, etc” but treated as actual physical wounds.