On occasion, time travel movies, time travel logic, or multiverse logic will make the rounds because of some popular piece of fiction. Many moons ago it was Back to the Future, and more recently Avengers: Endgame. A bit of a running theme in the popularity of these works is that to lack thinking of the specifics is to enjoy the movie. In both the cases mentioned, I'd say that's very accurate. It's almost a necessity of your expectation. Into the Spider-Verse can, in some realm, also be considered one of those movies. This is mostly due to a lack of focus on the spider-verse concept, and instead a mostly grounded story that centered around Miles Morales's origin story.
Across the Spider-Verse immediately differs from these aspects, as in some ways the meta narrative is the concepts of the multiverse itself. There are many pieces divulged to us by the characters on how the multiverse works; in fact, much of the second half of the movie centers around the main character's emotional force challenging these ideas. By extension, the movie almost makes explicit that Miguel O'Hara and the Spider-People are working on some sense of logic as to how the Spider-Verse works; canon events are detectable, they must occur, and these canon events build webs between the different universes. If too many canon events are stopped, webs will be broken, and eventually the Spider-Verse web will collapse on itself.
But I say some sense of logic precisely because the logic itself is inconsistent. To talk about why, it's important to dive into the concept of free will.
Forced Fatalism
Firstly, it's important to establish that the narrative that Miguel O'Hara and the Spider-People purport is a forced fatalistic perspective. I say forced because Canon Events can be stopped, although, in their belief, stopping them will have drastic consequences. Thus, they must be forced to occur by the Spider-People.
This perspective is evidenced by Miguel O'Hara's own personal origin story; he moved to a universe where his alternate self was dead, but his family was still living. By living in a universe that wasn't his own for too long, it caused the entire universe to get culled. It's important to note that the visuals demonstrated in this scene are of the universe experiencing many glitches.
Miguel O'Hara then says that Miles is a "mistake". The spider that bit him was meant to bite someone else in another universe; in essence, he was never meant to be Spider-Man, and his universe is the origin of all these mistakes.
I have a couple of proofs as to why this perspective is flawed:
Proof 1: Within universe logic, this anecdote can already be broken down as insufficient evidence for his perspective; when characters visit other universes, they not only glitch themselves, but cause their surroundings and what they touch to glitch. These phenomena are relatively unrelated to Canon Events; the cause of Miguel O'Hara's alternate universe to cull was his prolonged existence there, not the halting of Canon Events.
Proof 2: We also already know from the start of Across the Spider-Verse that, as long as people from alternate universes leave, then the universe will have no further consequence. More importantly, the actions from the Spider-People of other universes are incorporated into the canon of that universe, or at least, there are no "realigning" events where history is rewritten to where they never existed in that universe. Time just moves on like normal.
Proof 3: Miles Morales's universe discovered and interacted with the multiverse without any outside interference. What this means is that even if the fatalistic perspective were true, then Alchemax discovering the multiverse and bringing the spider from another universe is a part of the canon of Miles's universe. Miles is not a Spider-Man by mistake; it was supposed to happen in his universe. Miguel O'Hara slips up in his assessment; by implying that Miles is a mistake, he is also implying that Alchemax discovering the multiverse on their own was a mistake, thereby championing that Alchemax had a choice. Fatalism doesn't allow for choice; events are predetermined and inevitable.
Compatibilism
Now, it's important to mention that, in my belief, the Spider-Verse works under a compatibilist perspective; the other, imaginary choice is there; however, determinism is true, thus only one choice will actually happen. If none of the universes interacted with each other, then Canon Events as they are named would always happen as per determinism.
The "mistake" would come from the fact that both Miguel O'Hara's universe and Miles Morales's universe had a deterministic chain of events that eventually led them to break causality itself; by literally interacting with other chains of causality (universes), they would be able to change Canon Events. As long as alternative universe elements are present or were present in a universe, then the imaginary choice can become the actual choice.
In other words, the chain of determinism for that universe has been altered.
But the question then becomes this: so what? As far as the Spider-People know, there is no entity that enforces a chain of determinism to a universe. Miguel O'Hara's anecdote is likely to be the cause of an entirely different effect, as shown previously. Miles and Gwen's band will make the choices necessary to alter the chain of determinism in Miles's universe. But as long as they leave Miles's universe afterwards, then there is no known consequence. Time will move normally, as it had done in the time skip between the events of Into the Spider-Verse and Across the Spider-Verse.
Remaining Threads
I purposefully left out some mentions in the movie as their flaws didn't pertain to the argument behind this, and they can be broken too easily. I'll answer them here:
Black Hole in Spider-Man India After Halted Canon Event: The black hole was very likely to not be caused by the halting of a Canon Event, but by The Spot and his appearance in Spider-Man India. The events that led to the Canon Event were caused by The Spot in the first place, an entity that exists outside of Spider-Man India's universe. This is also further evidenced by the fact that the black hole looks and spreads the exact same way as The Spot's holes do. Miguel O'Hara mentions this as being "a consequence of stopping the Canon Event", but it is somewhat apparent to the viewers that the information is not entirely correct.
The Spot: The Spot exists because the collider was stopped in Into the Spider-Verse. It could be said that The Spot was created because the chain of determinism for Miles's universe was altered; however, when tracing back the events as The Spot does, he mentions that the original collider experiment that brought the irradiated spider from another universe was the beginning. Alchemax's experiments were part of the original chain of determinism for Miles's universe, and they had no external interference from another universe. There were two possibilities here:
1 (Imaginary). Miles and the band fail to stop Kingpin and the collider; The Spot is never created. Glitches become rampant as alternate universe entities exist in a universe that isn't theirs; Miles's universe gets culled ala Miguel O'Hara's anecdote.
2 (Altered Chain of Determinism). Miles and the band stop Kingpin and the collider explodes; The Spot is created.
In this case, the imaginary choice was always imaginary; the altered chain of determinism was always going to happen. In some ways, it could be said that using "altered chain" here is incorrect, as it may well be the original chain for Miles's universe, but I choose "altered" here as it involves multiverse interference through the irradiated spider and the other Spider-People.
Conclusion
To be honest, I don't even believe the writers were thinking about this as deeply as I am; Miles's conviction is, as mentioned previously, emotional in nature. He is "just doing his own thing" and disregarding the consequences. The point of this post was more of a hypothetical as to how the writers may have subtly demonstrated that Miles is not only emotionally correct in his conviction, but also accidentally logically correct. A proper and true exercise in over-analyzation. Whether any of what I said is going to be further elaborated on in Beyond the Spider-Verse, or whether I'm going to be proven completely incorrect will be revealed in 9 months time. I can't fucking wait.
