At its best, Twitter delights and instructs. Somebody, often somebody you wouldn’t expect, condenses the World-Spirit into a great joke, epigram, or aperçu. What oft was thought but ne’er so well expressed, you think, and favorite the tweet. Or: So funny, and you retweet. Pretty nice, also, when the ricocheting retweets say that the witty one is you! As for instruction, you can learn a lot from Twitter. Your Facebook or face-to-face friends may let you know what they think you should read, hear, watch. But are you friends with the famous environmentalist who, live-tweeting the apocalypse, tells you each time a new locality sets an April heat record in March? Or with Ludwig Wittgenstein, whose ghost had a feed? It’s an education to follow an experimental poet in Calgary obsessed with the digitization of art; a lefty Keynesian who’s crunched the numbers on student debt; an Occupier who reports whenever one of her comrades gets attacked by the NYPD. A tweet’s a narrow window, but nothing says that one of those can’t disclose — or, by way of URL compressers, link to — a big terrain.