AD&D1e: Abstractions work

Bill the Dungeon Delver does a regular livestream which you should subscribe to, and each week I join him to talk all things gaming. If you prefer video, watch - we get right into the guts of it from 22'40" in. This is the text version which is clearer but not as funny. 

We talked about how AD&D1e's abstractions just work. You shouldn't mistake precision for accuracy. Just because it's detailed doesn't mean it's right, and just because it's abstract doesn't mean it's wrong. Armour Class and Hit Points are not precise, but they're accurate. 

The first thing to say that all game rules must be subordinate to the referee's common sense. If a fighter in plate mail with 100 hit points is tied to an altar to the evil ape god Ollirog, the priest Thulsa Ook need not roll to hit or for damage, still less would they need to strike 30 or so times to sacrifice them to the hungry god. He's tied up and helpless, he will die. The wise player will endeavour to avoid the ever having to hear the blood-curdling cries of "ook! ook!" and finding the man-eating apes upon him. This discussion assumes the players and DM are not idiots, and we are discussing AC and HP in normal combats. 

In science, accuracy means how close the measurement is to the true value; precision means how exact and reproducible the measurement is. For example, I am actually 1.78m tall. If you measure me 3 times and the values are 1.75341, 1.75343 and 1.75340m, then the measurement is precise but not accurate. If you measure 3 times and the values are 1.82, 1.76 and 1.78, the measurement is not precise, but it is accurate. Ideally we want both accuracy and precision, in practice it's hard to get both, and there are all sorts of techniques employed to correct for this. 

It's a common tactic of sloppy journalists and unethical scientists (they're often friends) to confuse precision for accuracy. If we say that during a diet the average person's weight dropped 10.98438kg, this seems more credible to us than if we say "about 10kg." They hit you with precision to convince you of accuracy. 

In roleplaying game design there are similar considerations and issues. Commonly game designers will bombard you with precision to convince you their system is accurate. 

For example, GURPS has you account for every last gram of encumbrance, then asserts that the average person under ideal conditions can march 80km a day every day indefinitely, and can put 70kg overhead. It is precise, but not accurate. 

Rolemaster gave us critical damage and fumble tables, so you had something like a 1 in 200 chance that when you fired your bow you'd lose an ear. By the end of the Battle of Agincourt the English longbowmen would not have any ears left. It is precise, but not accurate. 

An abstract system like AD&D1e is imprecise - hit points, armour class, etc - abstractions, and abstractions are always imprecise - they're not exact, and they're not perfectly reproducible. The real question is whether it is accurate. I think it is.

Let's consider Armour Class. A common criticism of armour class is "armour doesn't make you harder to hit, it makes it harder for the hit to do damage", and this is true - but it comes to the same thing. 

1. Armour stops damage: Let's say your weapon does 4 points of damage, there is a 50% chance to hit someone and the armour will take away 50% of the damage - over several rounds of combat, 50% x 50% = 25% of the damage or 1 point will get through.
2. Armour makes it harder for you to be hit: With the same weapon, we now give you a 25% chance of hitting someone, but the armour takes away none of the damage - over several rounds of combat, 25% of the damage or 1 point will get through. 

So long as you choose the probabilities right - the to-hit roll changes and/or the damage resistance - the end result is exactly the same. However, the first option requires the to-hit roll and then subtracting the damage from the damage resistance, while the second option requires just the to-hit roll. It's simpler. It's an abstraction which works. Imprecise, but accurate.

Likewise Hit Points. These actually contain a few separate things, it's not sheer physical bulk and blade spongeiness. There are a few factors.

Combat stress. Anyone who has experienced a physical confrontation or trauma situation will know that their heart rate rises, they get tunnel vision, they become deaf and numb, they become clumsy and so on. Thus Mike Tyson's comment that "everyone has a plan until they get punched in the mouth." But someone who is more experienced with being punched in the mouth is more likely to be able to stick to their plan. They are accustomed to the adrenaline rush and can control it better. 

Parrying. AD&D1e has rules for parrying (give up an attack, and the opponent takes a malus equal to your Strength to-hit bonus, if any) which few ever use, and in any case are no use to average Strength characters. In the book Bounce, which is about mastery, the authour mentions how in his ping-pong club the players once went to an exercise science centre, and they measured everyone's reaction time - and the player who was known as the fastest measured the slowest reaction times. They scorned the exercise scientists' input from then on, but what was happening, he said, was that the player was anticipating the other players' moves rather than reacting to them - so his reaction speed wasn't as important. He knew from experience that when someone moved their shoulder this way, the ball was going to come that way, and so on. He knew the language of ping-pong so well he could finish other people's sentences. 

It's the same with combat, and an accomplished combatant will be able to do this better than an inexperienced one. Of course, doing this is tiring. But an experienced combatant can do it for longer. 

Fatigue. Combat is of course an act of physical exertion, but combat stress makes it more fatiguing than would doing the same movements without worrying about anyone trying to stab you. Again, anyone who's been in a fistfight or attended a car crash will know this - right afterwards you're exhausted. People practising CPR can go for hours, people actually performing CPR on a casualty need to swap out every few minutes at most. But experienced people can go for longer. 

The three factors of combat stress, parrying and fatigue are all abstracted in what we call Hit Points. Thus, a 5th level fighter with 28 hit points is not 7 times physically tougher than a Common Man with 4 hit points. But he is experienced in dealing with combat stress, he knows where his foe is going to strike almost before his foe does and can put his blade against it, and he's more combat fit.

Obviously, there is some upper limit to what is realistic in this regard. There is probably no-one in human history with the equivalent of 100 hit points, but there are probably many with 28. At higher levels, the game gets further and further from reality. But it is of course a fantasy adventure game. Nonetheless, the abstraction of Hit Points is not precise, but it is accurate - and it works.

But what about hit locations? Would that make it more realistic? Yes and no. In real world combats it's common for people to receive significant injuries and, because of adrenaline, not realise until after the combat - they still function. For game purposes all we're interested in is which of three states the combatant is in:

1. up and fighting unhindered
2. fighting, but hindered in some way
3. not fighting

Hit Points allow us to distinguish between #1 or #2 and #3, but not between #1 and #2. Hit locations would let us distinguish between #1 and #2 - maybe his leg is smashed but he can still sit and pling away with his bow, maybe his shield arm is broken but his sword arm still works, and so on. 

To some degree we can say this is something missing from AD&D1e, and it's said this was one of the things that gave us RuneQuest. But consider that the original Gygaxian game groups had a dozen players going for hours every night several nights a week. You can see why a DM wouldn't want to bother with hit locations. Consider also that as someone's Hit Points decline during a combat, they may start holding back, fighting more cautiously, and thinking about retreat - which is exactly what someone would do if they'd had a crippled limb, or found it harder to see, and so on. And so in ignoring hit locations, the abstraction of Hit Points is not precise, but it is accurate - and it works.

The last objection to the abstraction of Hit Points is healing. If only however many Hit Points of damage is a physical wound, given that natural healing 1 a day with rest, with a Constitution bonus each week - if a 28HP 5th level fighter and 4HP Common Man each fight down to 1HP, the 5th level fighter will take longer to get better. What?

Yes and no. The 5th level fighter takes just as long as the Common Man to heal up to 4HP - 3 days. In 3 days he's as good as the Common Man will ever be. But it'll take him most of a month to be back to himself, a 5th level fighter. 

This is actually realistic. In the real world we see that amateur boxers can fight a match every month, but a professional heavyweight only once or twice a year. And if someone does a top-level powerlifting competition and moves (say) 250kg, they can't do it again tomorrow - it's something they can do only a few times a year. Which is to say, low-level performances can be repeated often, top-level performances can't be. That 5th level fighter is going to achieve a lot more in a combat than will a 0-level Common Man. He does a lot, so he has to recover a lot. 

Once again, the abstraction of Hit Points is not precise, but it is accurate - and it works.

In conclusion, the abstractions of AD&D1e work. And that's why we're still playing it decades later.