ONE BY one, the disciplines of science have lost their innocence. For chemistry, the defining moment came during World War I, when the Germans unleashed an asphyxiating wall of chlorine gas on French troops. For physics, it was the 1945 obliteration of Hiroshima in a bright flash of nuclear fission. Knowledge brings power, and power can mean new ways to kill.
Now, looking ahead at the future of warfare, it appears that neuroscience will be next. Over the last decade, there has been remarkable progress in deciphering the signals the brain uses. The work is bringing new insights into disease, but could also be used to create a frightening new family of neurochemical weapons, designed to shut down particular brain circuits — or, eventually, to create highly agile killing machines, controlled by the mind.