Can someone please help me understand the difference between Predestination and Bootstrap Paradox by pointing me in the direction of movies that deals with each of them?

For instance, Predestination the movie seems to deal with Predestination Paradox, hence the name.

Can someone point me in the direction of a movie that deals primarily with the Bootstrap Paradox?

I am NOT looking for a list of movies, just looking to understand through an example.

• The Wikipedia article on the bootstrap paradox has an "in fiction" section which might help you get started. Mar 4, 2015 at 13:18
• Thanks @alexwlchan Wow, the most recent in the suggestions is from 1980. Mar 4, 2015 at 13:26
• Like I said, something to get you started, not a comprehensive reference. :-) Mar 4, 2015 at 13:29
• i really want to answer this but it's almost the definition of a list question (which I know because I started to write a list answer) Mar 4, 2015 at 14:40
• I focused on the "help me understand" part, hopefully that made a better answer. Mar 4, 2015 at 14:48

The two kinds of paradox are extremely closely related, so many times a movie which seems to deal with one actually deals with both. In fact, I've found quite a few places that consider them to be different names for the same thing.

In a predestination paradox, an event in the past creates a chain of events that leads to some second event in the future, but that second event is ultimately the cause of the first event. This is equivalent to what theoretical physicists would call a "closed time-like loop" (something that is "allowed", though extremely unlikely to be real, according to relativity.) The key here is that the action in the future only happened because the action in the past happened, but the action in the past was explicitly caused by the action in the future.

In a bootstrap paradox, an object (which could be a physical object, or a piece of information) is sent to the past, and the receipt of that object triggers a series of cause/effect, which ultimately leads to a future event whereby the same object is sent back in time. The key here is that the object/information did not come from anywhere. It exists because it always existed. (This kind of paradox is not, as far as I understand, even theoretically possible under relativity, it violates several conservation laws.)

## TV Shows

I know that you asked for movies, but really, TV shows are a much bigger pool of information on this stuff, if for no other reason than simple quantity. A good primer on both of these kinds of paradox is Doctor Who, since it involves quite a lot of time travel. An example of each (there are tons more):

• The highly popular, acclaimed episode Blink contains a bootstrap paradox: The Doctor (stuck in the past) reads a transcript of a conversation into a camera, which he arranges to be embedded on a DVD. A girl in the future watches the DVD and transcribes the conversation, then later gives the transcript to The Doctor, who takes it into the past with him to read.

• The mini-episodes Time/Space and Time Crash both feature The Doctor giving information to a future version of himself; it's much more explicit in Space.

• The episode Fires of Pompeii contains a (sort-of) predestination paradox. The Doctor finds himself in Pompeii just before Vesuvius erupts, and spends much of the episode trying to escape. It is later learned that he caused the eruption, in order to prevent a much worse disaster that would have resulted in the destruction of the entire Earth. Had he not done so, at the very least his companion from present-day Earth would never have existed, so he would never had taken her back to Pompeii, etc.

Many other TV Shows that deal with time travel mix the two up; the entire third season of Fringe is a giant bootstrap/predestination paradox:

Peter sent the blueprints for The Machine back into the past, along with some of it's parts, by using the machine that was built from the blueprints he sent into the past.

## Movies

As far as movies, it seems to be much harder to find recent examples of this; many time-travel movies these days explicitly avoid these two kinds of paradox by changing the future (Looper, Butterfly Effect, Days of Future Past, etc.) Both of these paradoxes involve a stable timeline -- nothing changes as a result of the time traveler. Most of the examples I found are from previous decades (or based on older books).

For the predestination paradox, other than Predestination, a good example would be:

• The Time Traveler's Wife: the protagonist travels through time meeting his wife at various stages: She only falls in love with him because he time traveled to meet her as a child, but he only visited her because they were in love in the future, etc.

For the bootstrap paradox, a few that I came up with:

• The Terminator series (specifically, 1 & 2): The original Terminator was sent back in time by Skynet to kill Sarah Conner; that Terminator is later found by Cyberdine, reverse-engineered, and used as the basis for Skynet. Thus, the technological information needed to build Skynet came from Skynet.

• Bill and Ted's Excellent Adventure: a very small one, but they only know to call Rufus "Rufus" because they hear themselves call him that; he never actually gives his own name.

There's also a lot of implied bootstrap paradoxes in movies, but they require a bit of assumption. For example, in Star Trek IV, Scottie gives an engineer the formula for transparent aluminum. If we assume that engineer patented that formula, and the rest of the world learned it from him, that would count. However, that requires us to reject the possibility that someone else independently discovered that knowledge on their own, which is something that happens all the time in science and math.

• But Predestination is also an example of a bootstrap paradox, since (spoilers!) the main character is a kind of "object" whose life forms a closed loop of sorts (or at least part of his body does--it would be analogous to an amoeba that went back in time, split in two, and then one became the younger version of the same amoeba that would later go back in time, while the other just aged and died). Mar 4, 2015 at 14:54
• Also, a clear example of a bootstrap paradox involving an actual physical object (rather than just information, as in your examples) can be found in the movie "Somewhere in Time", there's a watch in the movie that seems to have no origin--see the discussion here. Lastly, I disagree about the implied bootstrap in Interstellar--it would only be a bootstrap if Cooper sent the information back in time after being given it by humanity's descendants, but instead he and TARS actually discovered the information when falling through the black hole. Mar 4, 2015 at 14:55
• @Hypnosifl Yeah, that counts; there's also a predestination paradox in Terminator -- John Conner sends Kyle Reese back in time so John Conner can be conceived. As mentioned, lots of time travel movies contain examples of both. Mar 4, 2015 at 15:31
• (I took out the interstellar bit since I never actually saw the movie, only read about the science/math in it so I'll take your word for it. :) ) Mar 4, 2015 at 15:34
• One more point, I think your explanation here needs a little improvement: "In a bootstrap paradox, an object (which could be a physical object, or a piece of information) is sent to the past, and the receipt of that object triggers a series of cause/effect, which ultimately leads to a future event whereby the same object is sent back in time." This seems more like a description of a predestination paradox, which is not just any old causal loop, but a specific form of causal loop where a person's trip back ends up influencing their younger self to make that very trip. Mar 4, 2015 at 17:25