An open letter published today from 116 technologists, including DeepMind founder Mustafa Suleyman and (predictably) Elon Musk, calls on the United Nations to ban the development and use of autonomous weapons. The note warns that killer robots "threaten to become the third revolution in warfare."

It continues: "Once developed, they will permit armed conflict to be fought at a scale greater than ever, and at timescales faster than humans can comprehend ... We do not have long to act. Once this Pandora’s box is opened, it will be hard to close."

It is by no means the first time that such concerns have been raised—a very similar letter was signed two years ago. But calls for an outright ban aren't necessarily the best way to police this threat. As we've explained in the past, the advances required to create truly autonomous weapons are still a little way off. And other experts believe that a call to halt research and development may overlook ethical arguments that would be better thrashed out: robot soldiers could, after all, mean fewer deaths on the battlefield.

It is, clearly, an incredibly thorny topic. But it isn't clear that shutting down the debate entirely is the best route forward.