One obvious genius of the internet is that it’s “viral.” Information explodes to the whole world. The old neighborhood grapevine and the postal service seem like ox-carts in a speed-of-light universe. (Do twenty-somethings even know what those antiquities once were? In the old days, people had to talk to each other or stick a stamp on an envelope.) Instantaneous transmission produces some wonderfully good things. Truth, like joy, is infectious. A great idea feeds into a million inboxes. But it also produces some disastrous evils. Lies, rumors, and disinformation travel just as far and just as fast.