So the thought exercise is this: each player would take a slip of paper from a container without looking. Then they can look at the slip and hide it under something in front of them.
One of the slips says they are also a GM at the table! Lets say the number of slips of paper are equal to three times the number of players – so there’s about a one in three chance of a player being a secret GM – because they do not declare they are a GM. They sit quietly, as if just a regular player.
The point is, though, that the GM cannot try to just ‘run a story’, because if the ‘player’ who is actually their co-GM decides to reveal themselves, they can act like a GM just as much. And if the second GM tried to ‘run a story’, how would that work when it’s not the same story??
It wouldn’t. And that’s the point of this thought exercise – to show how each player is already like a mini GM, because they control one ‘NPC’ each. And you can change a lot of setting with one (N)PC – and more to the point, the player can attempt to run a story.
How will that work out? Well players already play their characters with the expectation that like in real life things don’t always go your way, it wont always go their way for what they do with their character/what they do with the story they run. This leaves players fairly flexible in regards to all of them running their own stories around each other.
Again, that’s the point of the exercise – it shows up whether a GM could handle there being another GM/is flexible like a player. The randomness of the slips would mean you can’t be sure there is another GM but you also can’t be sure there isn’t. You would have to bring together game world elements, but you couldn’t be sure you could just try and run ‘your story’.