Being the future inventors of time travel wasn’t all bad, of course. It was great to know that we’d never lose anything, never go to a movie that turned out to be a stinker, never buy a book we wouldn’t want to finish, never go out to a restaurant where the service was lousy, and never get stuck in a traffic jam, because we’d always be warned away, beforehand. It was terrific to have some future version of myself pop in just as I was about to irritate my wife with some inconsiderate comment and tell me, “It would be a really bad idea to say that.”

It’s not anything fatal. You know it can’t be anything fatal, because if it was, then there would be no future self who could be sent back to warn you.