It is not often the heads of two major companies blast each other in public, so Facebook CEO Mark Zuckerberg calling Tesla CEO Elon Musk’s artificial intelligence warnings “pretty irresponsible” on a Facebook Live broadcast was seen as a big deal.

Musk intensified the drama in response to a tweet, which said Zuckerberg’s “understanding of the subject is limited.” This is despite Facebook working heavily on AI and integrating narrow AI into some of its programs, and Zuckerberg building a home automation system.

“I have pretty strong opinions on this. I am optimistic. And I think people who are naysayers and try to drum up these doomsday scenarios — I just, I don’t understand it,” said Zuckerberg. “It’s really negative and in some ways I actually think it is pretty irresponsible. Because in the next five to ten years, AI is going to deliver so many improvements in the quality of our lives.”

AI will lead to faster cures for diseases, better match of drugs to the patient, self-driving cars, said Zuckerberg. He also said all technology could be used for good or bad, although Elon Musk has said previously that AI is different to other technologies, as it is a “fundamental existential risk to humanity,” whereas planes, trucks, and computers are not.

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In the most recent interview on the subject, Musk called for proactive regulation for AI, rather than reactive, as is the norm. He called for a collective halt of general purpose AI development, at least until researchers and governments can set the rules and limitations.

Musk is quite alone in this battle against AI, with Google, Facebook, Microsoft, and Amazon all forging ahead with their own research and development. There is also the argument that if not developed in the U.S., China will certainly take the lead in AI development.