Primer is by far the most sophisticated time-travel movie I've ever seen. Director Shane Carruth made a lot of efforts to untie any possible paradox.

As many others have, I've watched the movie quite a few times and read a lot of information about it. The following suggestion refers to the most common analysis of Primer's timeline, and can be seen in this Unreality Mag article, "At Last, A Definitive Timeline for Primer."

Primer Timeline - Unreality Mag

It is assumed that Aaron and Abe visit the party many times before making the successful move (where the gunman is arrested and Rachel is safe). But when you think about the mechanics, there seems to be a paradox:

In order to go back after a failed attempt (or just an observation), they must have a box running. But when they go back in time, in the new timeline, their doubles are also going to the party to make their attempt. Suppose the originals convince the doubles not to go, and let the originals go instead, since they have more experience. If they fail again this time, why would the doubles agree to stay in this timeline, where the party goes wrong? This implies both the originals and the doubles must go back together, which makes sum of series of doubles. Even if they stay in the hotel when the party is going, letting the ones that come out of the box go there, there are still two sets of each person stuck there if they fail.

I can't think of any conventional way they could have looped over the party more than once. In this theory, they got it right the second time, and sent back the doubles with explicit orders of what to do. The originals would then stay in this timeline, and these are the ones we see arguing at the airport. It is possible that the doubles would fail and get stuck with the new doubles, as explained above. In this scenario, they will not get to the same airport scene.

If I squeeze the juice out of this theory, and add that 1) Aaron mentioned the term "sum of series" at the beginning of the film, and 2) considering the mindf**k scene at the end where he builds a huge machine, this could support the theory that they failed multiple times and are trying to fix it (though this is a very flimsy theory).

Could anyone come up with a way they could loop back more than once?

  • 1
    The whole movie is a plot hole. Primer works because it creates good atmosphere by refusing to spoon feed plot points and using realistic props, not because it's accurate or coherent like all its fans try to make it to be. Commented Jan 21, 2017 at 2:54

3 Answers 3


The narrator himself (Aaron2) is an Aaron who encountered a future Aaron (Aaron3) who looped back to do the party a second time. Aaron2 himself has been convinced by Aaron3 to not do the party, instead letting Aaron3 attempt to perfect it:

"So I left. He had already performed the task as I intended to, by recording the conversations of the day just in case."

Any set of Abe and Aaron who encounter future versions of themselves who looped back to redo the party would possibly leave the timeline, but not right away. This is because the set of boxes that the future versions came out of would be the only ones currently running, and the "earlier" versions don't know what would happen if they attempt to shut the boxes off and use them. When Abe and Aaron encounter a future Thomas Granger who has used one of their boxes, Aaron alludes to this risk/unknown situation:

"I say we shut it off and see if he [Granger]'s in there."

When Abe and Aaron do get the party right, they manage a way to get the boxes shut off without any trouble. They loop back one final time and stay isolated in a hotel room. This is where we see Aaron sleeping, and Abe unable to. In this timeline, their earlier selves perfect the party, then shut off the boxes and vacate the timeline, leaving Abe and Aaron to argue at the airport.

I believe that any set of Abe or Aaron that is interrupted by a set of their future selves would then concede control of the timeline to that future set, and then leave town (probably) and try and create their own destinies/futures, just as Aaron2 did.

This is strongly suggested by the final warehouse scene: there are two Aarons here, each in his own warehouse, each building his own big box. Aaron3 (or...Aaron23) has just perfected the party and is clean-shaven. Aaron2 has just left town and the party to Aaron3, and is not clean-shaven.


There is a rather crude way to get this done. We know that Aaron and Abe are both capable of drugging their alternate selves unconscious. One of them could use two boxes and repeat this dark ritual multiple times, and then clean up the mess.

  1. Start box A.
  2. Start box B.
  3. If you receive a voicemail from yourself saying 'mission is go', use box A and go to step 1.
  4. If you encounter yourself, ambush him. Make sure no one finds him before the party.
  5. Go to the party. If you like how the party turned out, go to step 7.
  6. Use box B and go to step 2.
  7. Use box A.
  8. Start boxes A and B (to keep up appearances). Hide and leave yourself a voicemail saying 'mission is go'. Stay hidden long enough to be sure your double has used box A.
  9. Go to the party and repeat your successful choices.

When you are done with all this, there is only one copy of you and no one actually got ambushed after all. Cool huh?

There are some finer points that would have to be worked out, like how to cleanly arrange the situation so the right people get ambushed, but this should get it done with no lasting mess.

It is plausible that exactly this happened off camera. And it is only necessary for one person (Aaron) to do the going back and the ambushing. Abe doesn't have to be in on the scheme - in fact he shouldn't be in on it. Each time Aaron just coaches Abe on what to do, and after it's done, Aaron gets back in the box.

  • That's very clever! I assume (7) is a precaution for if (8) fails? What would they do in this case?
    – shay__
    Commented Dec 23, 2017 at 10:38
  • 1
    Actually I made a logical error. Fixed now, I think. But if your "final" party visit goes badly, you would need a third box like A to use as a failsafe, to be able to try again without having two copies of you in the final timeline.
    – wberry
    Commented Mar 15, 2018 at 1:45

Only the last revision to the timeline counts

In the world of Primer, only the final iteration of time travel truly matters. This concept is crucial to understanding the film's complex narrative and resolving apparent paradoxes.

Let's start with a key piece of narration from Aaron-2 (the hooded Aaron) about Aaron-3 (white jumper Aaron) (emphasis mine):

Aaron-2: I can tell you with certainty what I did that night when it was my turn.
But I think it would do little good, because what the world remembers, the actuality, the last revision is what counts, apparently.
So how many times did it take Aaron as he cycled through the same conversations lip-synching trivia over and over?
How many times would it take before he got it right? Three? Four? Twenty?
And eventually he must have got it perfect and it must have been beautiful with all the praise and adoration he had coming.
He had probably saved lives, after all.
Who knows what would have happened if he hadn't been there?

This narration suggests that while we might see multiple timelines in the film, only the final revision of events ultimately "counts." The Primer universe allows for timeline modifications in later iterations, effectively overwriting previous attempts.

Resolving the paradox: clones only appear when a time-traveler is prevented from making their journey

Now, let's tackle the paradox you mentioned about multiple versions of Aaron and Abe appearing at the party:

In order to go back after a failed attempt (or just an observation) they must have a box running. But when they go back in time, in the new timeline their doubles are also going to the party to have their attempt . Suppose the originals convince the doubles not to go, and let the originals go instead, since they have more experience. If they fail again this time, why would the doubles agree to stay in this timeline, where the party goes wrong?

The key here is that clones only appear when a time-traveler is prevented from making their journey. We see this when Abe-2 drugs Abe-1, and Aaron-2 drugs Aaron-1.

Remember the physical confrontation between Aaron-2 and Aaron-3? It resulted in Aaron-2 leaving town instead of using the time machine again. Aaron-2 explains (emphasis mine):

Aaron-2 [speaking as the narrator ]: And that's where I would have entered the story. Or exited, depending on your reference.
Because when Aaron came back the second time, it wasn't so easy.
He wasn't expecting me to put up a fight. And by that time, he was too exhausted to take me.
But for reasons that are only evident to me now, I understood that he simply wanted it more. That he just had more invested. So I left.
He had already performed the task, as I had intended to... of recording the conversations of the day just in case.
Through that earpiece he had a three-second lead on the world.

This scenario demonstrates how the film avoids the "sum of series" paradox you mentioned. Since the timeline is overwritten by the last revision, the doubles won't be going to the party in the final iteration. The last Aaron (Aaron-3) can simply repeat his actions to stop his doubles – drugging one and convincing the other to leave.

The concept of overwriting timelines is further hinted at in Aaron's conversation with Abe at the gas station:

The worst thing in the world is to know that the moment you are experiencing has already been defined, that this is the second or third time through, or whatever.

And do you ever feel like... maybe things aren't right, like maybe your life is in disarray or just not what you would like and you start to wonder what caused this. How did things get like this?
What if you knew for sure this is not the way things are supposed to be?

This dialogue suggests Aaron's awareness that their current timeline might be altered by future iterations.

Shane Carruth, the film's writer, director, and actor who played Aaron, offered some relevant insights into this aspect of the film (emphasis mine):

Question: Where did the title come from?

Carruth: First thing, I saw these guys as scientifically accomplished but ethically, morons. They never had any reasons before to have ethical questions. So when they’re hit with this device they’re blindsided by it. The first thing they do is make money with it. They’re not talking about the ethics of altering your former self. So to me, they’re kids, they’re like prep school kids basically. To call it a primer or a lesson was the easy way to go. And then there’s also this power they have in using the device is something almost worse than death. To put someone else in the position where they’re not sure they’re in control of anything. They’re not in the front of the line anymore and they’re living in someone’s past, to be secondary in that world. The thing that is most important is to feel like you’re at the front of the line, to be prime or primer. I definitely never wanted to say that in the film, but that’s where it comes from.

Source: DVD RE-RUN INTERVIEW: Shane Carruth on “Primer”; The Lessons of a First-Timer — IndieWire

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