I'm picturing a world (similar to that of Harry Potter) where some people but not all are able to use magic to change how people perceive the world around them. Unlike Harry Potter and others, the spells don't actually change the reality of the world.
A few conditions:
- When the spell is cast, it only affects people who would be able to see the object of the spell if they were to look at it. So, if Bob casts a spell on a rock in Paris, Alice, who's in London, will not be affected by Bob's spell. However, any 'immovable' object that would prevent a person from the seeing the object of the spell will also prevent them from seeing any of the spell's effects. For example, if Alice is on the right side of a ten-foot tall solid wall and Bob is on the left side, when Bob casts a spell on a rock (which is also on the left side of the wall) Alice will be unaffected because no matter how she moves (without changing her position) she cannot see the object of Bob's spell. On a flat plain the only thing that will prevent the spell from affecting everyone would be the horizon.
- You cannot cast spell if you do not have a direct line of sight to the object of your spell.
- You cannot kill with spells.
- You cannot circumvent condition number 1 or 2 by increasing your altitude (with the object of your spell) at the time of the casting which would extend the horizon line. There's a completely arbitrary limit of 100 miles because there's not enough "spell power" to cover more distance.
What would happen if a person who was not present at the time of Bob's casting (Person A) visited the rock Bob cast a spell on was asked to describe the properties of the rock to another person who was not there at the time of Bob's casting (Person B)? Both would share their view of the rock and they would obviously differ. The spell Bob cast changed the color of the rock from gray to green. Person B would say gray and the Person A would say green.
Who would be right? Neither is lying because that's how they see it. You can't say that the rock is actually gray so Person B is right because how would you know if someone cast a spell on the rock and made it gray and Person B was present for that spell but not for Bob's.
How (if possible) would disputes be settled in official settings? Imagine someone reports their car as stolen and tells the authorities their car is black and they find the car with matching plates and the right VIN but the car owner is charged with perjury because the car (as seen by the authorities) is red.
Also, people who are not able to cast spells don't understand how this is possible (magic is fake, just like in our world) and the people who can are not able to tell them.
Thanks for your help!