people have a very limited short-term memory. To be able to think complex and deep thoughts people need a way to surpass this limit.
External scaffolding such as writing allows us to swap out things from the short-term memory without a fear of loosing them. The [densely interlinked]([[evergreen notes should be densely linked]]) nature of notes allows us to faithfully serialize the context of our thinking and swiftly recover it afterwards.
Offloading the complex thought onto external representation also allows you to focus on improving the parts of the thought or argument without a fear of loosing the other parts of it. So you can work on your thesis part by part and then integrate it into the new whole