The Basic Rules give a couple definitions of roleplaying under “Social Interaction”. The first is a general definition: “Roleplaying is, literally, the act of playing out a role.” This tells us nothing about who determines what a particular role entails. The second definition is D&D-specific: “In this case, it’s you as a player determining how your character thinks, acts, and talks.” (emphasis added)
It isn’t me, or any other player at the table, that determines those things for your character. It’s you. And given that D&D is an RPG, that’s what we’re all here for, to make those decisions for ourselves. Anything that takes that away from a player (barring magical exceptions, of course) undermines the basic activity of playing the game.
However, this doesn’t mean there’s no mechanical option for influencing the thoughts and actions of another player’s PC. It just means the social interaction mechanics are not it. You have to work with the player, not against him/her. 5E has given us this lovely tool called Inspiration. By framing requests, arguments, threats, etc. in terms which speak to the personal characteristics of a PC, another character can gain influence over his/her decision making by creating an opportunity for that PC’s player to gain Inspiration, incentivizing an otherwise undesirable choice.
The premise of my games includes PCs’ personal characteristics being commonly known by all the players at the table, but even at tables where they aren’t, they could be learned through a successful Insight check as they can from NPCs.
A case that troubles me is thinking about Strength (Athletics) for a grapple, versus Charisma (Persuasion) to persuade. You, as the player, can't determine that your character isn't grappled, if you lose the contest against an NPC's Strength (Athletics). You could well say "
I walk away from the NPC", choosing not to ignore that your Speed has been made 0 in that situation: the skill check overrides your decision. So far as I understand, many people agree with that. Implying that perhaps many people agree that a skill check can override a player decision. A similar case can be made for Dexterity (Stealth). I think many people would agree that ordinarily, a player can't
decide to see a hidden PC or NPC.
This line of reasoning makes me hypothesise that it's not just about "
you as a player determining how your character thinks, acts and talks", because in the cited instances skill checks override that. You don't get to act how you want, if what you want is to walk away from a successful grapple or perceive a successful hider. For me this suggests a couple of options.
One option is that you get to determine how your character intends to think, act and talk, but that is then mediated through game mechanics. Overwhelmingly, that's what happens at the table. "
I decide to hit the Orc"... "
Okay, roll dice according to the game mechanics and we will see if your intended action happens".
Another option is that the above is generally true, except for certain skills, which are a special exception. I actually think this is fine as an argument, but what I want to know is why are they a special exception? I think we can point to a confounding aspect to social skills. In the case of being grappled, my game avatar has its speed made 0: nothing interferes with my intent to walk away. I just can't. Whereas with an application of social skills, such as a PC persuading me to stay put, it could feel like my intent is being rewritten: I can't even form an intent to walk away. I think this is ignoring the essential duality of the player-game relationship (see Miguel Sicart for more detail on that). What could really be happening in both instances is this -
#1 Clearstream the real life player forms an intent that Dross, their character and avatar in the game, will walk away. They tell the DM this.
#2a Dross is grappled. It's understood that Dross wants to walk away, but the avatar's speed is 0.
#2b Dross is diplomanced. It's understood that Dross doesn't want to walk away, regardless of the avatar's speed.
In each case, it's you - the player - that made all the decisions. Those decisions were mediated into the game world in different ways, depending on what game mechanics were in play.
Something like that is roughly the argument I'm looking at. I think so far it hasn't been addressed.