That all takes us to the nub of the problem. It’s natural to trust one’s own senses, to believe what one sees—a hardwired tendency that the coming age of manipulated video will exploit. Consider recent flash points in what the University of Michigan’s Aviv Ovadya calls the “infopocalypse”—and imagine just how much worse they would have been with manipulated video. Take Pizzagate, and then add concocted footage of John Podesta leering at a child, or worse. Falsehoods will suddenly acquire a whole new, explosive emotional intensity.

But the problem isn’t just the proliferation of falsehoods. Fabricated videos will create new and understandable suspicions about everything we watch. Politicians and publicists will exploit those doubts. When captured in a moment of wrongdoing, a culprit will simply declare the visual evidence a malicious concoction. The president, reportedly, has already pioneered this tactic: Even though he initially conceded the authenticity of the Access Hollywood video, he now privately casts doubt on whether the voice on the tape is his own.

In other words, manipulated video will ultimately destroy faith in our strongest remaining tether to the idea of common reality. As Ian Goodfellow, a scientist at Google, told MIT Technology Review, “It’s been a little bit of a fluke, historically, that we’re able to rely on videos as evidence that something really happened.”