I’ve been trying to write this post at least a dozen times. I don’t mean this figuratively; at one point, I literally had a desktop folder with a dozen abandoned drafts. They had wildly different styles—from rigoruous to chaotically cryptic and insufferably meta; they would start abruptly, chew on themselves, and eventually trail off to nowhere. One by one, I threw them all away because they all sucked. It turns out that I wasn’t really writing a post; I was actually preparing a talk. I was pret...