In time travel, a stable time loop occurs when the root cause of an event can ultimately be determined to be that event itself. A typical example is when a hero goes back in time to prevent something bad from happening, only to cause the very thing he was trying to prevent. If the event in question would obviously never have happened if it weren't for the loop, this is derogatorily referred to as a predestination paradox.
If something comes into existence merely by virtue of being part of a stable time loop, this is referred to as an ontological paradox. A stock example is a time traveler who tells his past self everything he needs to know to become a time traveler; where did the information come from?
The same trick is occasionally used to create actual objects out of nothing, too, especially time machines. However, this requires one to overlook the fact that technically such an object would need to have perfect durability/an infinite lifespan, not losing even so much as a single atom each pass.
Game and Story Use
- One of the things about this that bothers philosophers most yet is most valuable for writers is that anything, no matter how implausible it would otherwise be, can "plausibly" happen as part of a stable time loop. It can also happen at any time, and ontological paradox gives even more freedom.
- Furthermore, if the chain of events is long and convoluted enough the audience might not even notice that it's a predestination paradox!
- Through ontological paradox, any character can be "plausibly" given any information at any desired point in the story.
- Ontological paradox can be used as a rationale for a supernatural ability that lets a character temporarily create and use any desired item.