In Steven Spielberg’s sci-fi masterpiece “Minority Report,” set in the year 2054 and released nine months after the attacks of September 11, 2001, homicide-squad detectives no longer spend their time tracking down people who have committed murder. Instead, they go after people who are about to commit murder, swooping down to stop them in the nick of time. Spielberg’s police officers don’t fight crime, they fight “Pre-Crime.” They don’t catch killers, they catch pre-killers.
The enormous anti-terror establishment that the United States has created in the years since 9/11 has a similar purpose. Its vast, sprawling, expensive array of governmental, quasi-governmental, and nominally private institutions and their tools—high tech, like ubiquitous surveillance cameras, satellites, wiretaps, computer algorithms, facial-recognition software, drones, and data collection and analysis on a global scale; lower tech, like networks of agents, bags of cash, and airport security checkpoints—are designed primarily to stop acts of terrorism before they happen. That turns out to be a good deal more difficult than investigating such an act once it occurs.