Aristotle broke ground by claiming that the art of persuasion—rhetoric—can be learned. Although Aristotle was right, he may never have envisioned a day when a machine could also be taught to argue. It took 2,300 years for it happen, but it happened.

On Monday, February 11, I had a front row seat for the first live debate between human and machine. For six years, scientists at IBM Research have been working on the next big milestone for artificial intelligence (AI). First, Deep Blue beat a chess champion in 1996. Watson beat a champion game-show contestant on Jeopardy in 2011. Would an AI machine beat a world record-holding debate champion in 2019?

The hundreds of invited audience members gave the win to…the human. But IBM’s “Project Debater” still made history as the first AI machine to make a persuasive argument about a given a topic it had not been programmed to learn.

Harish Natarajan holds the world record for most international debate victories. Monday’s debate was the most unusual—and perhaps the most challenging—he’s ever had. After all, Project Debater had access to 10 billion sentences in hundreds of millions of documents. Natarajan had no access to the Internet. He just had a pen, his notepad and his brain.

Each side—human and machine—had 15 minutes to prep for the debate. They were each presented with a topic: “Should we subsidize preschools.” Project Debater had to argue in support of it. Natarajan had to argue against it. Once again, he had only his brain, persuasion skills and a remarkable human ability to connect with an audience.

IBM’s AI machine went first. She presented a reasoned, logical 4-minute case to support her opinion. She focused on three areas: preschool boosts a child’s academic achievement, it helps to overcome poverty, and it results in a decrease in crime. The machine scanned millions of documents, retrieved the relevant messages to support its opinion, and presented scores of studies and empirical research to back its argument.

According to scientists who worked on the project, the achievement is nothing short of extraordinary. Project Debater structured an argument, only presented evidence to support its case, listened to Natarajan’s argument and formed a rebuttal.

In this video, you can watch IBM’s AI Machine open her speech.

Natarajan used a more nuanced form of persuasion—one that would resonate with fellow humans. Natarajan told me that great persuaders find common ground with their opponents. And that’s exactly what he did.

“First, I’d like to focus on what agree on,” he began. “Poverty is terrible. It is also terrible when people don’t have running water or healthcare to cover their child…”

Natarajan used his time to argue that, while funding preschool is a laudable goal, we live in the real world of financial constraints and there’s a limit to how much we can spend. He argued that Project Debater’s position would hurt the very people it intends to help by re-directing scarce resources from other worthy initiatives.

At the end of the debate, the live audience of 800 guests were invited to vote. Since more people said that Natarajan had turned around their pre-formed opinions, he was declared the winner. After all, the point of debate is not to score the most points. It’s to sway a person’s opinion.

IBM’s AI machine wasn’t built to “win” or replace humans. It was built to complement human decision-making. According to the research team that built the machine, it’s meant to enhance communication with evidence and reason. No, AI doesn’t have emotion. It can’t read an audience or connect to people on an emotional level. But it can structure reasonable arguments backed by millions of studies, documents and empirical evidence.

Project Debater’s arguments were “nicely phrased and contextualized…better than most humans,” Natarajan told me after the debate. “It has incredible power to complement the human.”

Aristotle believed that in order to convince people to change their minds, a speaker must have a combination of ethos (character), logos (logic, reason, and evidence) and pathos (emotion). Aristotle argued that all three elements had to be present for persuasion to occur. IBM’s Project Debater is short on emotion. It doesn’t have the imagination to even dream itself up—that’s the exclusive domain of the humans who built her. But she does have something valuable to offer human decision-makers—evidence, reason and logic.