Two years ago Stephen Hawking told the BBC that the development of full artificial intelligence, could spell the end of the human race.
His was not the only voice warning of the dangers of AI - Elon Musk, Bill Gates and Steve Wozniak also expressed their concerns about where the technology was heading - though Professor Hawking's was the most apocalyptic vision of a world where robots decide they don't need us any more.
What all of these prophets of AI doom wanted to do was to get the world thinking about where the science was heading - and make sure other voices joined the scientists in that debate.
That they have achieved that aim was evident on Wednesday night at an event in Cambridge marking the opening of the Centre for the Future of Intelligence, designed to do some of that thinking about the implications of AI.
And Professor Hawking was there to help launch the centre. "I'm glad someone was listening," he told the audience.
In a short speech, he outlined the potential and the pitfalls of the technology in his usual vivid language. He reviewed the recent rapid progress in areas like self-driving cars and the triumph of Google's DeepMind in the game of Go - and predicted further advances.
"I believe there is no deep difference between what can be achieved by a biological brain and what can be achieved by a computer. It therefore follows that computers can, in theory, emulate human intelligence — and exceed it."
That, he said, could lead to the eradication of disease and poverty and the conquest of climate change. But it could also bring us all sorts of things we didn't like - autonomous weapons, economic disruption and machines that developed a will of their own, in conflict with humanity.
"In short, the rise of powerful AI will be either the best, or the worst thing, ever to happen to humanity. We do not yet know which."
More: http://www.bbc.com/news/technology-37713629