Berkshire Hathaway billionaire Warren Buffet is wading into politics, saying he has one question he’d like to ask of every candidate running for U.S. president in 2020.

Buffett has previously weighed in on whether or not he thinks mega-CEOs like former Starbucks head Howard Schultz (no) or Michael Bloomberg (yes) would make a good president, and he says he chiefly wants to know how they deal with people who disagree with them.

Per CNBC:

“I want to hear what they tell people who disagree with them,” Buffett told Yahoo Finance on Monday. “I would like to ask a candidate: ‘What are you for that the majority of your followers are against?’”

That’s the best way to be sure that a candidate really believes in a particular issue, according to Buffett.

“That’s really the test,” he says in the interview.

Those comments from Buffett came in response to a question about whether the billionaire would ever ask a candidate what they think about the economy or other issues. Buffett laughs and points out that any candidate would probably just “tell me what I want to hear” to win his support, which is not what the billionaire would want.

For Buffett, being strong-minded but having enough respect to hear out someone with a different opinion or point of view is a positive thing.

For example, Buffett and his Berkshire Hathaway right hand man Charlie Munger, “disagree on a few things,” Buffett told CNBC in 2018, and that’s often been helpful.

“Charlie, he’s given me a lot of good advice over time,” Buffett told CNBC in a 2016 interview. “And, I may hate to take it to a certain degree, but sometimes — but my decisions have been better. I’ve lived a better life because of Charlie.”

Billionaire Ray Dalio also thinks listening to those who disagree with you is essential. It’s a hallmark of the culture that Dalio has created at his hedge fund, Bridgewater Associates, which he calls “radical transparency.”

“I just wanted to see things through [employees’] eyes and to have them see things through my eyes so that together we could hash things out to discover what’s true,” Dalio said.