The day is saved by Louise speaking in a language she doesn't speak, an appropriate climax for a film all about interpreting language.
The Chinese government is the one that assumes most strongly the aliens have belligerent intent and are accordingly hostile? Is it because they're the US's main geopolitical rival and it's movie produced in the US? Or is it because they have experience with a foreign culture showing up and imposing its will through force, to the country's substantial detriment? Maybe intentional since the author of the original story is the child of immigrants who came to the US after fleeing the Cultural Revolution?
During their first meeting, Ian tells Louise that she was wrong about language being the cornerstone of civilization, arguing that science is instead. What Ian failed to consider is that science is only useful in a civilization if you can find a way to communicate about it. The Heptapods need to be able to communicate with the humans before they can share anything else with them.
Interestingly, Contact would argue the opposite. Without common concepts, there is no way to learn to communicate.
Incidentally, the line Louise wrote that language was a weapon in her book? She probably was influenced by future events to write that line, just as she was dreaming/remembering a daughter she wouldn't have for a few years.
A bit of Fridge Heartwarming, but when the Heptapods decide to help humanity in the present, since they will need our help in the future, as far as their nonlinear time perception is concerned, we have already helped them in the future. In a way, they're thanking us for something we are yet to do.
There's a couple of possible reasons for why Ian happens to be reading a copy of Louise's book. One of them is that he already happened to be reading it and brought it with him when the military picked him up. Another is that he knew ahead of time that Louise was being considered for the mission, and got a copy of the book to get smart on her. A third possibility is that the book was already aboard the helicopter, belonging to one of the military personnel who were trying to learn about her as they were on their way to pick her up (indeed, the book might be Colonel Weber's).
Each of those possibilities hints at the reveal since each implies a basic level of foresight through the medium of language. That is, having read or otherwise been told who they will be working with, they prepared for encountering her before it happens.
More like Fridge Tragedy: When Louise and Ian enter the ship, unaware of the bomb, Ian notes that "Abbott" is absent. Abbott appears moments later. Why did Abbott take longer to come out? Because, thanks to the alien's nonlinear time perception, he knew he would be walking to his death. Despite living his entire life knowing the moment he would die, when the time came he still needed to take a moment, to prepare himself. And then when he can't warn Louise and Ian to leave, he gives his life to save them. The Heptapods are far more like humans than they appear.
Do you remember that song? The one called "On the Nature of Daylight"? Among other places, it was also used in Shutter Island. You may remember that in Shutter Island, there is a house with a lake close behind it. Just like there is at the start of Arrival. You may also remember that, in Shutter Island, the mother who lives there kills her children. In Arrival, the narrator talks of how memory doesn't work the way she thought it did. And we learn that learning the alien language allows one to see what will happen in the future, and what we thought were memories are actually scenes of the future. So our memory of the music from Shutter Island might accomplish this same thing in the viewer, a prediction of what will happen! Cool, huh? Indeed, in Arrival, not only does the child die, but also the mother knew this would happen and chose to let it happen. I'd even go so far as to wonder: is this a (brilliantly communicated) commentary on the morality of having children or something? It's neat, anyways!
Louise chose Hannah, and when her husband finds out the situation he says she's "made the wrong choice". However, she could not have made any other. If she had said No to him, the palindrome could not exist and therefore the retroactive memories/future seeing could not have helped her break the language barrier with Abbott and Costello. Hannah was a necessity and Louise decided to make it the best she could.
To add to this, Louise likely explained this to him. Meaning he has to live with the guilt of now knowing not only what will happen to his daughter, but that his wife knew, and if he had never asked her then his daughter would never have had to suffer her fate.
He was probably angry that she chose not to tell him that their future daughter would die young.
The movie never shows what happens after Hannah's death. It's entirely possible that Ian and Louise reconcile at some future date, when Ian comes to understand circular time and her choice better.
General Shang had been working with the Heptapods as well, and it's suggested that everyone who learned the Heptapods' language would be able to see both ways in time; remember, the Sapir-Whorf Hypothesis states that languages shape thought. He went to the conference knowing he had to close the time loop. In fact, it's strongly hinted that since humanity learned the Heptapods' language, there was world peace because everyone could see the future would be A-OK.
Then why would he still launch an attack on the Heptapods? Perhaps he did not understand, as Louise hadn't until the Heptapods explained it to her personally, what was happening to his comprehension of time. And when Louise told him his wife's dying words, he understood because he had the same vision she had of the conference. Louise in present time giving him words that she only could have known if the conference were to happen finally tipped him off about the reliability of his new abilities.
Heptapods are a logical non-human sapient, because most biologists think the next sapient species on Earth may be cephalopods.
Once you realized how Heptapods perceived time, the movie (especially the ending) made far more sense. We perceive time linearly (past —> present —> future) and only a few humans could "see" otherwise. The Heptapods perceived time spherically - the present at a point on the sphere, past and future timelines radiating outward from it around the circumference of the sphere, intersecting at one point on the other side - You Can't Fight Fate. This is perceiving time the way we perceive space. Einstein, Kip Thorne and Steven Hawking would have had an absolute field day with Heptapod thinking — an entire alien species that could perceive time the way only the most advanced human mathematicians could!
And because of this time perception (and a fair amount of Ultra Tech) they could essentially build giant TARDISes and travel through time and space freely, allowing them to find humanity at just the right time to bootstrap our technology with a gift of their knowledge and ultimately come full-circle to help them in their hour of need, 3000 years in the future.
When Louise's brain gets "re-wired" by her learning the alien language, why does she first experience it as something akin to hallucinations? Well, it wasn't intended to be processed by (likely far more primitive) human brains. The film suggests that Louise can only see into the future for a decade or two, for at least as long as Hannah's life. What have the Heptapods managed to learn about the universe, when they have access to 3,000?
Perhaps it's because Louise doesn't know the full language? She knows enough to see a bit into the future, sure, but I highly doubt she understands the proper formation of every single possible word in existence. Another explanation I can think of is that Louise had only known he language for such a short time. Maybe the longer you know the language, the further out you can look.
And maybe people don't need to or want to look into the future, and prefer to experience things freshly.
Or, it could be like being in a moving car. You can see vaguely what's coming, but it doesn't become clear til it gets closer.
According to the book, it works in spurts, during times you need to know the future, and you don't just see the future, you see the past too — at the same time. In addition, the Heptopods themselves are a sort of "signal boost" for her.
Many of the creepy elements in the meeting hall of the Heptapods might have actually been attempts at making humans more comfortable. A straight, linear corridor, a glass that only allows observation from a single direction, fog that will ensure that humans don't have to observe too many things going on at the same time — it may all have been the Heptapods' imperfect idea on how to make a species that can only observe time and space in one direction at a time feel at ease. This may even have been why they crouched with all their limbs bending in one direction, even though they can clearly move more naturally by "swimming" in the air, and symmetrically spread all their appendages around them.
When it comes to all the questions raised about why the Heptapods did any given thing, the repeated theme seems to be why did they allow Marks onto the ship/not use as much human language as they got when they knew it all along thanks to their time-perception/come to earth at all when they are about as close to omniscient as a being could be? Even with all that knowledge, whatever threatens them in 3,000 years is not within their power alone to do anything about it. They have perfect knowledge of what's coming, when, and thousands of years to try to prevent it without getting humanity involved. Yet they believe their only option is to uplift humanity so they can aid the Heptapods in the future. It's not just that the Heptapods saw that humans would help them in the future; they know that that is the only path time can take. They allowed Marks onto the ship because preventing the bomb's detonation was not an option. They're not trying to prevent paradoxes because paradoxes can't happen. Information can be transmitted through their perception of time, but the power to change the future does not come with that information.
Ian named the two Heptapod ambassadors "Abbott" and "Costello". These names prove to be appropriate as Abbott and Costello based a lot of their humor, notably their best known sketch, "Who's On First", on two men attempting unsuccessfully to communicate with each other.
The reveal is telegraphed early on by the very tone of the movie: Ian wonders whether the aliens arrived via Faster-Than-Light Travel. Since this is Hard Sci-Fi, the laws of physics dictate that any FTL ship must ALSO be a time machine.
When Ian joins Louise in taking off his hazmat suits, he comments that "everybody dies". That comes off as bit of bravado about taking a risk, but it's actually a very poignant commentary on what Louise's final perception of times means. Seeing all time together forces you to accept that everyone eventually dies. Even if Hannah wasn't going to die young, Louise would have still been aware of her death from the moment she was born. So being a parent means that you have to focus on and be grateful for the time you have, while being painfully clear that it's not going to last.
One of the brief flashbacks/flash-forwards shows tweenage Hannah shouting "I hate you!" (presumably at Louise). Age-Appropriate Angst? Or did she just find out her mother knew she was Doomed by Canon (either by someone telling her, or by learning Heptapod)?
Just what are the Heptapods going to need help with? What kind of crisis could occur that a highly advanced, future-seeing race can't deal with on their own without uplifting humanity (and possibly other species)? The implications are not pleasant.
On the other hand, this is a somewhat human-centric way of looking at the question, it still assumes a causality. From the Heptapod perspective, causality evaporates; things just are. It could be something that would be, to our own perception and linear worldview, in fact quite trivial; perhaps not easy, but nothing that requires interstellar travel and uplifting a random primitive civilisation. But to the Heptapods' perspective, there is no other choice, that is just how it happens. They didn't develop interstellar travel thinking of reaching humanity to uplift us so that we will save them, they do it because that is just how things will happen. You Can't Fight Fate.
It could simply be that Humans Are Bastards or even Humans Are Cthulhu. We're good at killing things, maybe in no small part because we have no trouble distinguishing beginnings from endings. Heptapods have trouble conceptualizing "weapons" to the point that they either weren't able to communicate a distinction between weapon and language - or they believed that the bomb WAS a form of human language. (Why else would we bring it to them?)
Another possibility is that the "quantum blindness" that humans have while unaware of the future allows us to change it in ways that are physically or mentally impossible for the Heptapods, but some of us still had to learn to "open time" to save our species from mutually assured destruction. This could be why Abbott pounded on the barrier trying to alert Louise and Ian to the bomb despite knowing it would be too late: they may have been aware of the eventual ability of humans to change the future, and hoped against fate that it would manifest this soon.
Regardless of what the Heptapods will need help with, is it a good thing to give humanity in general the ability to see into their personal futures? Who knows what someone will do to try to change things if he/she sees a future they don't like? This is assuming they can even change it.
The power of the language implies that there is no free will. While the characters may feel like they have made choices, ultimately if the future is predetermined, they haven't made a choice at all.
Fridge Brilliance within Fridge Horror: Of course none of the characters have any free will. Being characters in a work of fiction, they're at the mercy of the author. The Heptapod language lets them read the script without quite letting them know about the Fourth Wall.
Louise takes the revelation of her doomed daughter in stride. This kind of foreknowledge might drive others insane if their future turns out to be even less pleasant.
The way the story explains free will, or the lack thereof, is that if you imagine a person being able to read a diary which details their own life, then the obvious question is if one can then act against what is written. However, there is another possibility. Reading the diary may in fact create an urgency in oneself to carry out all the actions described therein. So Louise and the Heptapods are aware of how things play out, but accept their fate, and aren't distressed by it.
This might stretch to WMG territory, but while Louise's encounter with the Heptapods in their own atmosphere, without any protective gear appeared to have no lasting effects, it's possible it may have had something to do with Hannah's illness.
The doctor in the scene when the find out about the illness appears to be checking her lymph nodes. This is often used to determine the presence of an infection, which certainly gives this impression, but this could also indicate lymphatic cancer. However, there is no scene of her being examined after her encounter with Castello at the end, and the facilities for examining her afterwards would have been dissembled in the evacuation. Even if the facilities were still intact, she would already know she's infected, how many people she would have transmitted it to, and that there's nothing she can do to prevent it from spreading to Hannah.
Lymphatic cancer isn't transmittable (at least in humans), you can't spread it to someone else the way you might the flu. Do notice, however, that there is a constant worry about radiation: the military constantly mentions radiation readings, and they wear NBC protection. It might have caused a single fateful mutation in the one egg inside Dr. Banks's ovaries that was destined to become Hannah and develop lymphoma. Seems like in this universe you reallycan't fight fate.
If the case is that Heptapods experience their own lifetimes nonlinearly, but otherwise don't have a way to predict the future, that must mean that some of them that are alive right now will experience the crisis for which they'll eventually need humanity's help. That means they live for at least several millennia, and yet Abbott still didn't hesitate to give their life to save 2 vastly inferior humans who themselves only have a moment, relatively speaking, left in their own lives. Rewatching the movie, it's hard not to feel like you can see the fear and desperation in Abbott's attempts against fate to instruct the humans to escape the bomb as Abbott's final memory closes in towards the present.
Furthermore, Abbott doesn't die instantly in the explosion. Costello writes the next day that "Abbott is death process" likely implying a slow and painful demise, if they experience anything resembling pain. Abbott would have experienced this horrific future during every moment of their life.
