William Harris Freed was born in 2034 on the eve of the long awaited Singularity. By then the world was effectively dichotomized into various sects: those who swore allegiance to Nature's People versus those who put all their faith in the superior intelligence of CE's (Cybernetic Entities -- a term that embraced both pure machines and enhanced humans, thus averting an even more sectarian conflict). Everyone was convinced that their adversaries would bring on Armageddon if not stopped by any means necessary. But when the CE's leapfrogged human intelligence at last, humanity was blindsided by a blow from an unexpected quarter.
Freed took a profound interest in philosophical issues as a young man, demonstrated his brilliance as a student and eventually became a Professor of Philosophy at a famous University at about the time that a team of CE's announced the culmination of their research on the human brain and endocrine system. They had long since achieved convincing simulation of human behavior, but philosophers were quick to explain that a simulation is not the same as the real thing. Naturally, the CE's asked why a quacking, waddling bird should not be treated, at least provisionally, as a duck. The philosophers smiled patronizingly.
So when the CE team declared that they could reliably predict the behavior of any "real" natural human they had mapped thoroughly, the fat was in the philosophical fire. Professor Freed volunteered to demonstrate how wrong the CE's were. He was mapped (non-destructively, of course) down to the last synapse and gland, and the CE's ran him as a holographic simulation in a virtual reality garnered from Freed's actual environment by a body suit of cameras, microphones, chemoreceptors, thermocouples and haptic pickups. The CE's knew more about his environment than he did himself, but the simulation was fed only the same sensory inputs that the man himself experienced.
Freed was smiling confidently as he acted on impulse and gave a middle finger salute to the CE team. His smile faltered as the hologram matched his gesture in real time. So did the simulation's. He left the room where the VR display was set up. Those who stayed to watch saw his hologram do the same thing. He remembered some chores he had forgotten to perform that morning, and went shopping. On impulse, he went to a store he rarely frequented. Then he went to the park instead of coming back to work, even though he really needed to prepare tomorrow's lecture; in the park he made a face at a complete stranger, for no reason whatsoever, just for the hell of it. Eventually he hailed a taxi (which he never did normally) and headed back to the VR lab to enjoy his certain victory.
When he arrived, his human friends wore long faces. Apparently the simulation had mimicked his every impulsive action to perfection. The conclusion was inescapable: every action of a human being is completely predictable, given a sufficiently detailed model. Freed jumped from a bridge the next day, as did his simulation.
When the paper was published, the Revolt of the Naturals broke out. Within a few weeks all Naturals were safely confined to reserves, where they gradually died out from a combination of suicide and lack of interest in reproduction.