The belief that all human behaviors flow from genetic or environmental factors that, once they have occurred, are very difficult or impossible to change.
When the heptapods land, humans don't know what they are or what they are doing.
They go inside and investigate, try and learn the language and what they are doing.
They try to destroy the pods, but are very unsuccessful.
Trying to decode their language seems impossible, they understood some things (to their own knowledge) but weren't really getting somewhere. Communication wasn't working. Puzzle pieces then started to connect.
Some factors are extremely hard to change and some even impossible, determinism is the main focus, the main theme, once it has occurred, nothing they can do but try.