This was a comment I made in response to a post from mathematician and science writer Jordan Ellenberg:
In many ways, science is science communication. Our first audience is ourselves. It’s no joke that “writing it down” is often a key step in understanding. And anyone who’s tried to write a textbook or expository article realizes that true clarity requires true understanding. I’ve done huge amounts of research in order to write a paragraph here or there in a book. Because I wanted to make it clear to others, which first meant making it clear to me.
P.S. Given the comments, I was perhaps not clear enough above. My point was not merely that scientists communicate with other scientists. My point was that, in doing science, I spend a lot of my time communicating to myself. The writeup is not merely what it takes to get published, it’s also often what it takes for me to formulate and understand what I myself am doing.