“In order to exploit this particular quality of idea formation, he keeps what he calls a ‘spark file’: ‘A single document where I keep all my hunches: ideas for articles, speeches, software features, startups, ways of framing a chapter I know I’m going to write, even whole books.’ He doesn’t try to organize them. The randomness is intentional. He reads them over every few months and finds themes emerging — connections between fragments that wouldn’t seem apparent if those fragments were presented in isolation.”