Many technologies seen in science fiction stories simply exist to enable the plot.
A common example is faster than light travel, as in Star Trek's Warp Drive. Without faster than light travel, it would be difficult to have stories about ranging all over the galaxy and seeking out new life. If it took hundreds of years to travel between stars, as conventional physics suggests as a best case, there wouldn't be much time for adventuring.
Antonym: the Deus Ex Machina.
A Deus Ex Machina is a violation of the fictional world in order to move the plot. The classic example is the a god being lowered to the stage in a Greek tragedy for the purpose of rescuing the hero from being killed by an angry mob, or something such, particularly when there is no anticipation of such a thing being possible in the minds of the viewers. Imagine watching a typical Western, set in the 19th-century, where the hero is tied to a railroad track, and there's a steam train barrelling toward him at full speed. Just as our hero is about to be crushed by the locomotive, a UFO appears from nowhere and incinerates the train with it's raygun. *That's* a Deus Ex Machina.
Machina ex deo?
No, the term comes strictly from theatre: as partly noted above, the god character solved problems by himself, without gadgets, but came on stage lowered by a suitably impressive machine. The machine was a typical trait of the problem-solving god that made a flashy entrance at the end, whereas other god characters (e.g. disguised ones) behaved more plainly.
In Life Of Brian by Monty Python, Brian is being chased by Romans when he falls off a building to a certain death, but falls into a passing alien space craft. Handy.
A Plot Enabling Device, on the other hand, *is* consistent with the fictional world. When Captain Kirk is beamed aboard the Enterprise just as a foe is about to clunk him over the head with a battle axe, the action is consistent with the fictional world. The viewer already knows that such things are possible in the Star Trek world.
There's a middle term here, too: consider the unanticipated and utterly non-sensical, but plot-crucial "Obi-wan not getting there in time" apparatus featured in Star Wars I (while the Sith takes on his master) and IV (when everyone else got back to the Millennium Falcon in time). This kind of gadget aids the plot, and while not violating the conventions of a fictional world in the way that a Deus ex Machina would, also doesn't have an justification for existing in that world, either. See the "choppy, crushy things" in the movie Galaxy Quest for further discussion. -- Keith Braithwaite
(Galaxy Quest Chompers could be a page all to itself (and now is), as there are countless examples of similar "does that have any other purpose than to cause drama?" that most of us Tv Watchers take for granted.)
Plot Enabling Devices usually are inconsistent, in that they usually have implications which are not adequately explored. For example, Doctor Who is not about what it would be like to have a time machine. The time machine is merely a plot device to get the Doctor to his next adventure. It is typically used twice per story, once at the start and once at the end.
To prevent too many unlikely miracles, such as jumping back in time to correct a blunder in episode 3, the Doctor's time machine is out of repair and cannot reliably make short hops.
The implications of the Star Trek transporter are not often explored. For example, if we can transport things, why can't we copy them? Some of this did get developed in the later series, in the form of the Holodeck. -- Dave Harris
Some of the implications did start to be explored in Star Trek Voyager, where unexpected things did happen quite often with the transporter - IIRC in one episode they hid a large group of refugees by dematerialising them and keeping them in the transporter buffer for a while. Also, in the episode Symbiogenesis, a bizarre transporter mishap resulted in two of the crew members being merged into one person. (Yes, that's very unlikely, but this is Star Trek we're talking about... :)
This reminds me of a poem from the Hitchhiker's Guide to the Galaxy by Douglas Adams:
I teleported home one night With Ron and Sid and Meg. Ron stole Meggie's heart away And I got Sidney's leg.
Contrariwise, on TNG they knew that it was possible to duplicate a being via transporter, but when they tried to restrict Data to stay in a research facility, using his uniqueness as a reason, they did not suggest duplicating him in the transporter - which Star Fleet would have had the authority to at least suggest, since they were claiming Data was not a sentient. -- Pete Hardie
Star Trek has far too many plot-enabling devices by now. So far, the transporters can duplicate objects, split people in two, combine two different people, and oh yeah, reverse the aging process. Not to mention the rampant use of time travel to work miracles. There's no rigid set of limitations on the capabilities of the protagonists, and that's why the next Star Trek series is going to be a prequel. You can write stronger stories when you don't have a universe where 99% of conflicts can be resolved through magic. -- Nick Bensema
Which, I believe, makes Star Trek writing a classic example of the "slippery slope".
Star Trek is only a TV show.
Your point?
That there are other TV shows?
The positronic brain of Isaac Asimov's robot stories might be a Plot Enabling Device. When someone asked him how the positronic brains were supposed to work, and why positronics should be superior to electronics for the job, he said he simply didn't know.
But the implications are effectively nil. Daneel's brain could be an artifact of pure bolognium, but that wouldn't require any changes to the plot at all. It's scenery.
I'm bothered by the lack of demarkation here. Space fiction has two fundamental questions that must be addressed in some way (1) how do we get somewhere interesting? ( Answers: FTL, Warp drive, Warp Points, Hyper Drive, Improbability Drive, Bergenholms ....) (2) how do we talk to the people we meet there? (Answers: Universal Translators, Lens, Babel fish....)
If that's what a Plot Enabling Device is, then the term should exclude plot elements (i.e. the Death Star, which is the motivation for the action in A New Hope) and Sonic Screwdrivers (teleporters, and other magic gizmos applied to various predicaments).
I'd always thought the Brian-falling-off-the-tower thing was a reference to one of the temptations of Christ - where the devil urges him to prove himself the son of God by jumping off a tower and having God dispatch his angels to catch him?
A related term used in The Science Of Disc World (by Terry Pratchet, Ian Stewart and Jack Cohen) is Narrativium Substance. A substance present in the universe of most fantasy and obviously many science fiction universes, that facilitates the narrative story line.
Compare with: Deus Ex Machina, Mc Guffin
See original on c2.com 