In the pursuit of security, state actors presume a linear relationship between the lethality and complexity of various means of attack. They deploy resources and research programs to overcome the inherent or "analytic" complexity of increasingly lethal means of their own (think of programs to develop nuclear weapons and other highly lethal munitions), and they impose security, legal and regulatory regimes to increase the imposed or "synthetic" complexity opponents must overcome to appropriate or adopt the means they develop. Nonstate actors such as terrorists overcome the challenges of complexity by imaginatively seeking new ways to operate in an alternative high lethality/low complexity space. The perversity of their imagination allows them to conceive of means of attack beyond the pale for state actors, leaving states initially unprepared to defend against them. Car bombs, vehicle ramming and small arms attacks on dense crowds, and iconic attacks such as 9/11 are examples of nonstate actors successfully operating in the high lethality/low complexity space. Successful attackers will continue to do so in ways that state actors fail to imagine and protect against, especially when the prevention of low-complexity attacks traditionally falls on local governments with fewer resources, and they employ means that do not have especially suspicious signatures. The deployment of weaponized drones against crowds and other soft targets may indicate one of the evolutions of this operational space. State security requires fully understanding the imagination of the nonstate actor, but good governance requires balancing the necessary thinking and preventive measures with the freedoms of a state not burdened by such a perverse outlook.