While the act of writing can be useful on it own, the text one creates can be a great help in future thinking. If you Write small, self-contained notes, and give them good titles, they become easy to build upon in other notes. Treat your notes as an API, as building blocks and stepping stones to become familiar with and build upon. This chunking of ideas helps you think about things at higher levels of abstraction, and takes things which might have been difficult to think about before, and makes them easy. One note can also constrain other notes. This is a special case of The Use of Knowledge.