But going back to
@pemerton 's original question -- what ARE rules for?
Some of Vincent Baker's thoughts only make sense in the context of a game where there's a need to carry over gamestate information across situational contexts, and where the conceptualization of the "rational actor" that exists changes as the situational context changes.
For example: consider taking
Keep on the Borderlands and literally just playing the combats in some sequence. There's no gameplay at all of any kind between the combat sequences. The GM literally concludes a combat, and immediately shifts to the next site of combat and says, "Roll initiative," and instructs the players that all expended resources are immediately available again.
Very much like just playing 5 or 6 Heroclix combats in rapid succession, with no intervening roleplaying, exploration, etc.
If you played
Keep on the Borderlands in this fashion, have the rules of D&D provided anything that any other set of wargame mechanics could not? Could you not swap out the D&D combat rules for the Heroclix combat rules, or the Gloomhaven combat rules, or the Journeys in Middle-Earth combat rules, or the Mythras combat rules, or the GURPS combat rules, and achieve largely the same experience?
Sure, some of the underpinnings and choice / resolution factors change, but at the end, either you've conquered all of the combats as a team, or you have not.
But the second you introduce a "rational actor" gamestate into the mix, something fundamentally changes. For example, after say, Combat 3 of 6 in the
Borderlands sequence, one of the players is allowed to say, "Hey, we just killed Orc Leader #6. Doesn't that change something about what we're required to do next? Am I allowed to say now that my cleric pawn is no longer interested in continuing these battles, because conquering Orc Leader #6 was his whole motivation all along, and he has no need to continue?"
What fundamentally changes about the game being played if that's the case?