Those are good points, ndkid.
I'd just put out there that some people will play D&D foremost as a game where you come across problems and solve them, and other people will play D&D foremost to take on the character's perspective and interact with situations.
Secondly, if the game is meant to challenge the player's problem-solving skills, it doesn't make sense to have a rule where you roll to solve a problem. If it's meant to challenge a player's communication skills, it doesn't make sense to roll to communicate effectively. I think D&D wasn't intended to challenge the player's ability to fire an arrow, or to search for secret doors.
I think it was intended to challenge the player's ability to plan for circumstances in which he's need a bow and arrows (encumbrance minigame), to select a good encounter strategy (melee vs. archery, spells, use an item, flaming oil, sneak away, negotiate, etc.) in the former example.
And in the latter example, to know when would be a likely time to search for secret doors (accurate mapping, suspicion of local monster activity and egress, noticing clues like scrapes in the floor or tracks that end at a wall, etc.), to decide whether it's worthwhile to search (time management - chance to find a secret vs. time wasted causing random encounter checks).
For these reasons I'd say the player should choose whether to shoot an arrow, but a roll should be made for accuracy. The player should choose whether to search, but a roll should be made for success.
Similarly, your negotiation strategy should be chosen by the player, but the character's ability to carry that out would be a roll. You could try to bribe a guard but fail. Less likely would be an inadvertent seduction.
This follows the typical pattern for D&D interactions with the environment: the player declares an attempt and the DM determines the outcome, giving the player feedback on what happened. The player can say "I jump to the moon!" and the DM would refer to the character's jumping ability and probably say "You jump and jump but don't get much higher than 3' or so".
One could argue that a dumb player can't come up with a plan that his smart character would come up with. But coming up with the plan is player skill. Executing the plan is character skill. If your player skill is not up to snuff, you should watch, learn, ask questions, read, try harder; improve. You get better at something if you persist against challenges.
The specific example, of a player with high CHA paired with a character with low CHA, would result in the player figuring out a great way to talk to the NPC (maybe this guard is known to be underpaid, overworked, and of low morale - thus susceptible to bribery) but his character rolls with his low CHA score and may botch it.
A player with low CHA paired with a high-CHA character will probably come up with lame approaches ("hey baby, wanna come back to my place?" to the guard who was just talking to his buddy about how much he loves his wife) but is more likely to pull them off because the character rolls with a high CHA - even with the penalty due to the lame plan.
A player with high INT but character has low INT would come up with an awesome plan to set up a Ponzi scheme, but when rolling his character would probably fumble some details and it would end up not working.
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@sambojin: I used to think a good DM fudged dice rolls. That is was important for the game to go on, for people to have fun. People get attached to their characters and their magic items. They frequently want to experience cool stuff they don't get to experience in their daily lives.
Then I changed my mind and thought a good DM was fair and honest, presenting clear challenges and letting the players decide what to do - let the dice fall as they may. If the players decide to fight a dragon and they're way too low level, don't lower the HD of the dragon. Don't reduce the breath damage. Don't let them get super high save bonuses because after they attack they all say they're hiding behind their shields. Through hardship there is growth. You don't appreciate wealth until you're poor, or success until you fail.
Then I changed my mind and currently think a good DM is someone who runs a game, tells his players the truth, and if they enjoy it and stick with the game that's wonderful. I personally play and DM as the second paragraph because that's what I think is best. I don't want to play in a game where there is no risk of loss, except what loss the DM decides to cause and which is unavoidable. I'm not going to tell you that your description of a game is the wrong way to play it, or that it sucks (because I'm sure there are plenty of players who think that's perfect), but that it's not for me.
Understanding that, is it really plausible for you to claim that "a good DM ... ignores what the dice roll was" with the unspoken corollary that it is a bad DM who sticks with the rules and dice results?
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Finally, and I hesitate to bring this up because it's strawmannish, but it sounded like you were saying a DM should change rules at a whim and ignore them if it's inconvenient for him. That seems like a pretty dick move to me.
Example 1: The rules say werewolves need a silver or magic weapon to hit, but a PC succeeds in charming one. A DM could say "oh he's on your side now so he can be hit by any weapons, because I don't want you guys to have that ability".
Example 2: Flaming oil in the game does 2d6 damage the first round, 1d6 the second, but only 1 hp per round if it's a splash or you move through it. You've got a werewolf that needs a magic weapon to hit - which is to say it's immune to non-magical daggers, swords, maces, arrows, etc. The players planned well and all bought oil. They strategized well and all threw oil at the same time, then someone threw a torch. They got really lucky and a lot of them hit. The damage would destroy this "boss werewolf" in one round, and you had intended the battle to go on for some time (including some exposition by the Boss just before he ducks into a secret door and escapes). The DM says that the flaming oil counts as a non-magic weapon because it isn't magical fire, so the monster is immune. Then you splash a vial of acid on it and he says the acid isn't magical so it's immune. Remember that the game will note when a monster is resistant to fire or acid, and this monster doesn't have those notes.
Example 3: Intelligent ravenous monsters attack the PCs, and get some really lucky hits in. The PCs all go down. The monsters then lose interest in the PCs and their living horses and wander off without taking any treasure. The horses drag the PCs back to town where everyone is nursed back to health - even the dead.
(By the way, all of these happened to me as a player)
So, are these the sort of circumstances in which you'd advocate the DM ignore rules and fudge things? Because in my game (1) werewolf keeps his resistance and makes a great, though problematic, servant, (2) boss werewolf dies horribly and everyone high-fives ... there are plenty more challenges to come, (3) either the monsters eat the PCs and we roll up a new party, or the living ones wake up in their den (like the Hoth wampa ice cave thing in star wars) and need to figure out how to escape!
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There's this argument that whatever the DM says, goes. And that's great if he's not a dick DM. The wonderful thing is you can always leave that shitty game and play with cool people.