Beware engineers! In their examination of individuals involved in violent extremism of all kinds, Gambetta and Hertog find engineers to be massively overrepresented in right-wing movements, both secular and religious. Not all engineers are violent extremists, of course, but an astonishing proportion of right-wing (but not leftist) extremists are engineers. The authors hypothesize that engineering attracts individuals who yearn for order, social “purity,” and some mythical halcyon days of yore. The argument is not watertight, but it is data-driven and carefully constructed. Gambetta and Hertog take a close look at jihadist engineers, many of whom started promising mainstream careers in the 1950s and 1960s. At that time, they were hailed as the future leaders of newly independent states in the Muslim world, but in the 1980s, they crashed against a wall of failing economies, cronyism, and corruption. Some of them went on to become the architects of utopian Islamist movements and demonstrated no qualms about using violence. Although engineers belong to both violent and nonviolent Islamist movements, they seem particularly drawn to the violent variety.