Elon Musk, Steve Wozniak and other tech industry leaders called for a brief pause in artificial intelligence research in an open letter publicized Wednesday.

“Should we let machines flood our information channels with propaganda and untruth?” the letter reads. “Should we develop nonhuman minds that might eventually outnumber, outsmart, obsolete and replace us? Should we risk loss of control of our civilization?”

The letter was issued in response to OpenAI’s GPT-4, the artificial intelligence engine behind ChatGPT. The signees want a six-month pause on “the training of AI systems more powerful than GPT-4.”

In a recent statement, OpenAI leaders said, “At some point, it may be important to get independent review before starting to train future systems.” The letter’s authors responded: “We agree. That point is now.”

Even though many artificial intelligence pioneers signed the letter, no one from OpenAI joined them, according to TechCrunch.

“In some sense, this is preaching to the choir,” OpenAI CEO Sam Altman told the Wall Street Journal. “We have, I think, been talking about these issues the loudest, with the most intensity, for the longest.”

Altman said his company has not started training GPT-5 and spent six months doing safety tests on GPT-4.

The letter does not just focus on OpenAI, however. It expresses concern about a “dangerous race to ever-larger unpredictable black-box models with emergent capabilities” — an apparent reference to a quote from Microsoft CEO Satya Nadella.

“In fact, a race starts today in terms of what you can expect,” Nadella said in his own Feb. 7 letter. “And we’re going to move; we’re going to move fast.”

Musk, the highest-profile signatory, was a co-founder of OpenAI but left the company’s board in 2018 and has since criticized its direction. However, he’s also launched his own artificial intelligence initiatives with somewhat less success.

“Society has hit pause on other technologies with potentially catastrophic effects,” the letter read. “We can do so here. Let’s enjoy a long AI summer, not rush unprepared into a fall.”