If it’s unclear where to draw the line on autonomy, then maybe intent is a better way to think about such systems. Lethally autonomous defensive weapons, such as the Phalanx missile defense gun, decide on their own to fire. Dodaam Systems, a South Korean company, even manufactures a machine gun that can automatically track and kill a person from two miles away. These stationary, defensive systems have not sparked the outcry autonomous drones have. “Offensive systems, which actively seek out targets to kill, are a different moral category,” Krishnan explains.

Yet many experts are uncertain whether autonomous attack weapons are necessarily a bad thing, either. “Can we program drones well? I’m not sure if we can trust the software or not,” Samuel Liles, a Purdue professor specializing in transnational cyberthreats and cyberforensics, wrote in an email. “We trust software with less rigor to fly airliners all the time.”

The judgment and morality of individual humans certainly isn’t perfect. Human decision-making is responsible for some of the worst atrocities of recent conflicts. Just on the American side, massacres — like when Marines killed 24 unarmed civilians in Haditha or Marine special forces shot 19 unarmed civilians in the back in Jalalabad — speak to the fragility of human judgment about using force. Despite decades of effort to make soldiers less likely to commit atrocities, it still happens with alarming regularity.