“The ancient Romans built elaborate networks of pipes to deliver water where they wanted it to go. The networks were a marvel. But many of the pipes were made of lead, and the water carried the lead along with it. One school of thought regards this as part of the reason for the decline and fall of Rome: lead poisoning gradually took its toll, impairing the thought and judgment of many Romans, especially at the top. The theory is much disputed; perhaps it contains no truth. But as a metaphor it is irresistible. We have built networks for the delivery of information—the internet, and especially social media. These networks, too, are a marvel. But they also carry a kind of poison with them. The mind fed from those sources learns to subsist happily on quick reactions, easy certainties, one-liners, and rage. It craves confirmation and resents contradiction. Attention spans collapse; imbecility propagates, then seems normal, then is celebrated. The capacity for rational discourse between people who disagree gradually rots. I have a good deal more confidence in the lead-pipe theory of the internet, and its effect on our culture, than in the lead-pipe theory of the fall of Rome.”