A hundred years ago, Europeans could not have imagined the horrors that lay ahead for them. Our current century was ushered in with an awful demonstration of what may lie ahead for us; can we make the adjustments necessary to avoid the worst? “I’d like to think we can do that before there’s been a disaster,” writes Stewart Baker, “but, really, I’m not sure we can.”

That prognosis is more than a little unsettling, given Baker’s résumé. As general counsel to the National Security Agency (the Pentagon’s foreign-electronic-surveillance arm) during the presidency of George H. W. Bush, he was a staunch privacy advocate. …