The professor was still teaching at the time and doing research. It's always hard to tell with him because he was so humble, but it may have been an inception sort of thing. I'd often go into the room and he'd sometimes he'd take sections of the book. And then I'd end up in coffee shops dotted all over Cambridge with headphones in,. Not listening to music but listening to clay talking to try and master the art of like, "This is how to write my section"