Two of the world’s richest and most intelligent men are arguing about the future of artificial intelligence (AI).

Elon Musk and Mark Zuckerberg are locked in a very public feud over artificial intelligence.

Musk has repeatedly warned about the dangers of AI, describing it as a potentially existential threat to the human race.

Zuckerberg has a different take. On Sunday, he took questions live over the internet while barbecuing beef brisket at his backyard in Palo Alto, California. He responded to a question about Elon Musk’s warnings by saying he was tired of the fear-mongering.

“With AI especially, I’m really optimistic,” Zuckerberg said during the live broadcast. “I think that people who are naysayers and kind of try to drum up these doomsday scenarios – I just, I don’t understand it. I think it’s really negative and in some ways I actually think it is pretty irresponsible.”

Musk shot back on Tuesday morning with a tweet saying, “I’ve talked to Mark about this. His understanding of the subject is limited.” He added that a movie on the subject of AI was “coming soon,” but didn’t provide details about the film or his involvement.

Musk ignited a global discussion on the perils of AI in 2014. He predicted that humans might be doomed if we make machines that are smarter than us. He said in a recent interview that his warnings haven’t been heeded.

Musk, who’s leading space exploration projects and major tunneling initiatives, is now trying to develop AI that he hopes will have a positive impact on humanity. He’s heading up a startup that intends to build devices to connect the human brain with computers.

Zuckerberg is no stranger to AI. He worked last year on developing an artificial intelligence system to help run his life and his home. After about 100 hours of work, he posted a video at the end of 2016 showcasing an AI system called Jarvis, which is voiced by the actor Morgan Freeman.

In his broadcast, Zuckerberg said AI could be a force for good because it helps power self-driving cars and diagnose illnesses. “If you’re arguing against AI, then you’re arguing against safer cars that aren’t going to have accidents. And you’re arguing against being able to better diagnose people when they are sick. I just don’t see how, in good conscience, some people can do that. I’m just much more optimistic on it than probably a lot of folks are,” Zuckerberg said.

“In the next 5-10 years, AI is going to deliver so many improvements in the quality of our lives,” he added.

Musk, who has been warning about intelligent robots causing massive job losses and potentially gaining uncontrollable autonomy, responded to Zuckerberg after a social network user posted the tech billionnaire’s comments.

Musk, founder of a space company, says humans have to consider colonising other worlds and even merging with machines to maintain the upper hand over robots that “will be able to do everything better than us”.