Here's why the ending to Arrival (2016) makes no sense

In this video, we explore the logical inconsistencies that ultimately break Arrival's ending, but do not deter it from being a fantastic film regardless.

DETERMINISM:
Determinism is the philosophical and scientific theory for a single, certain future, and it goes a little something like this:

Imagine, for example, you had a pot of water and you put it on a hot stove. What's going to happen? Well, the water will probably boil. If you leave it on long enough, the water will probably evaporate entirely. In fact, if the water DIDN'T boil, it would be very concerning.

We know that water boils when it gets hot. We know that if you jump, you'll come back down again because of gravity. The universe is full of physical laws that DETERMINE what are the outcomes to any given scenario.

The theory of determinism states that if we were able to quantify the infinite amount of variables present in the universe at a particular instance in time, it would be possible to determine the future with 100% accuracy. That is the gist of it.

If the future could be determined, than free will is made irrelevant. The only reason this is not case in our universe is because of the strange things that occur on the quantum level. Particles exist in several place at once, they pop in and out of existence, and in and out of time, apparently at random. This randomness forbids a deterministic universe, as there will always be uncertainty in every variable. I urge you to read the wiki page if you're still interested in this topic!