What are the origins of terrorism? ‘The reign of terror’ explains that the notion of terrorism, or terror, came from the French Revolution. The terror transformed the Revolution from a liberating to a destructive force. Those who instigated the terror had to find justification for their violent killing. Their motivation provides a key to the distinctive nature of modern terrorism. The revolutionaries may have seemed to act as crusaders, but the Reign of Terror was informed by the Enlightenment assumption that human agency can change the social order. The French Revolution’s use of violence created a model for the application of terrorizing force by state actors that lasted two centuries.