Forgotten Phlebotinum: Difference between revisions

* A very subtle version of this happens in L. E. Modesitt's ''Spellsong Sorceress'' cycle. In the first chapters of the first book, a spell is cast that teleports the main character in from Earth. It's implied that although the lady casting this spell isn't a very strong sorceress, she can still send people to locations halfway across the continent with a bit of help. This use of magic is never mentioned again, despite the fact that it would be tremendously useful in a variety of circumstances.

* ''[[Harry Potter (novel)|Harry Potter]]'': Sirius' two-way mirror, which is basically a magical walkie-talkie. In Harry's defense, he was never told exactly what it was, and swore never to use it for fear it would cause Sirius to come to Hogwarts and get arrested and/or killed. It still qualifies as forgotten phlebotinum, however, because even after Harry has gone through great risk to speak to Sirius through Umbridge's fire, it didn't occur to Sirius to tell him "Next time, use the mirror I gave you." which would have {{spoiler|saved his life}}.

* Science Fiction author [[Larry Niven]] coined "Niven's Law," which states that once a technology is introduced into a setting, it must continue to be present in all later stories in that same setting.

** Civilization-wide Forgotten Phlebotinum can be somewhat justified if there are [[No Plans, No Prototype, No Backup]], or if the civilization enters a Dark Age when lots of stuff is forgotten, but Niven's Law is still a good rule of thumb. At any event, once the technology has been proven to work once, then the natural laws which permitted it to happen must remain consistent from then on, regardless of whether the tech is ever rediscovered.