The cardinal rule of RPG epistemology is that nothing about the game is true or real until it's been said and understood ("established") at the table.

DMs lose sight of this because they track dozens of things they plan to say - but plans are not reality.

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It's not CHANGING what's behind the door if you decide the room is full of skeletons instead of kobolds BEFORE it's opened.

It NEVER WAS kobolds.

You only PLANNED to make it kobolds.

When you establish that it's skeletons, it HAS ALWAYS BEEN skeletons in the game world.

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From the DM's chair, it FEELS like a change.

From the player's chair, it feels like it was ALWAYS skeletons.

In the fiction, it has ALWAYS been skeletons.

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Playing a GMless RPG will make this VERY clear to you VERY quickly. Your intentions in a GMless game DON'T MATTER unless you talk about them.

The other players are also basically GMs, and since they don't know your intentions, they will run right over them and never look back

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None of the game world is true in the real world. (DUH)

It only exists in the imagination, and only what exists in the SHARED imagination is true in the shared game world.

This goes for GMless games AND traditionally GMed games.

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This is why it feels weird when a player has their character act confidently on a player assumption that contradicts an idea (plan) the GM had about the world. The GM feels that their un-established idea is true, and the player thinks something was established that wasn't.

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"I use my Banish Ghosts power to buy you all time to escape. This only lasts a minute, so run fast! I'll catch up!"

(But I wrote down 'faeries' not 'ghosts'! It's not haunted, it's infested with gremlins!)

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Epistemically, they're both wrong:
- It's not established to be ghosts
- It's not established to be faeries

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In a traditionally GM'ed game, the player's assumption does not establish a game-world truth.

The GM must now establish: "Your power doesn't work! The doors all slam shut, blocking your escape and proving that these aren't ghosts..."

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Like everything else in shared fictional worlds, the fact that "these aren't ghosts" only became true after you said it.

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As a GM, you probably FEEL like it was true before, because it was in your notes and had the power to establish it at any time, BUT IT WASN'T.

You had the AUTHORITY to make it true before. You have the authority to make it true now - even against the player's assumptions.

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Prep (faeries, kobolds) is not truth until it is spoken into the game world.

The reasons we prep are:
- Continuity
- Planning ideas (conflicts, threats, opportunities, flavor, details, surprises) to put into the game world

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Of these two, CONTINUITY is why GMs think it's important to respect your prep.

And you SHOULD respect your prep! It saves you from breaking continuity!

But your prep is still not TRUTH.

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Continuity is "reminder: 3 sessions ago I established that there are kobolds in the dungeon, so I write, 'room 6: 4 kobolds'."

Your prep is still not truth, but it's an important continuity note. Changing kobolds to skeletons breaks continuity.

You have to fix it somehow.

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But remember: You can establish in the game-world-before!

You can just add room 7 to your map and put kobolds in it.

The time that matters to the table is when the information is established in the real world, not when it was added to your prep.

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Changing room 6 from kobolds to skeletons and then adding room 7 and putting kobolds in it doesn't change the game world.

It doesn't change the past in the game world.

It just changes your plans for stuff to add to the game later in real world time.

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The skeletons were only established to be in room 6 at exactly 9:32pm on Friday night, December 18th, 2020 when you said, "...you see 4 skeletons!" In the game world, nobody knows exactly when they got there. "Before" but how long before? Not established.

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They did not get there at 3:39pm when you wrote "Room 6: 4 kobolds"

They did not get there at 9:27pm when you crossed out "kobolds" and wrote "skeletons"

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Your un-established prep is a truth that never was.

Nor is it a truth that "will be."

It's always a "maybe." Remember that.

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As you get better at improvising as a GM, you'll find it's better to leave intentional blanks in some places and to prep three or four possibilities in others, most of which will be thrown out.

Your prep becomes less a script, more a toolbox.

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