The Limits of Political Debate | The New Yorker
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In 2016, a debate champion was consulting on the project, and he noticed that, for all of its facility in extracting facts and claims, the machine just wasn’t thinking like a debater. Slonim recalled, “He told us, ‘For me, debating whether to ban prostitution, or whether to ban the sale of alcohol, this is the same debate. I’m going to use the same arguments. I’m just going to massage them a little bit.’ ” If you were arguing for banning prostitution or alcohol, you might point to the social corrosion of vice; if you were arguing against, you might warn of a black market. Slonim realized that there were a limited number of “types of argumentation,” and these were patterns that the machine would need to learn. How many? Dan Lahav, a computer scientist on the team who had also been a champion debater, estimated that there were between fifty and seventy types of argumentation that could be applied to just about every possible debate question. For I.B.M., that wasn’t so many. Slonim described the second phase of Project Debater’s education, which was somewhat handmade: Slonim’s experts wrote their own modular arguments, relying in part on the Stanford Encyclopedia of Philosophy and other texts. They were trying to train the machine to reason like a human.
In February, 2019, the machine had its first major public debate, hosted by Intelligence Squared, in San Francisco. The opponent was Harish Natarajan, a thirty-one-year-old British economic consultant, who, a few years earlier, had been the runner-up in the World Universities Debating Championship. Before they appeared onstage, each contestant was given the topic and assigned a side, then allotted fifteen minutes to prepare: Project Debater would argue that preschools should be subsidized by the public, and Natarajan that they should not. Project Debater scrolled through LexisNexis, assembling evidence and categorizing it. Natarajan did nothing like that. (When we spoke, he recalled that his first thought was to wonder at the topic: Was subsidizing preschools actually controversial in the United States?) Natarajan was kept from seeing Project Debater in action before the test match, but he had been told that it had a database of four hundred million documents. “I was, like, ‘Oh, good God.’ So there was nothing I could do in multiple lifetimes to absorb that knowledge,” Natarajan told me. Instead, he would concede that Project Debater’s information was accurate and challenge its conclusions. “People will say that the facts speak for themselves, but in this day and age that is absolutely not true,” Natarajan told me. He was prepared to lay a subtle trap. The machine would be ready to argue yes, expecting Natarajan to argue no. Instead, he would say, “Yes, but . . .”
The first time I watched the San Francisco debate, I thought that Natarajan won. He had taken the world that Project Debater described and tipped it on its side, so that the audience wondered whether the computer was looking at things from the right angle, and that seemed the decisive maneuver. In the room, the audience voted for the human, too: I.B.M. had beaten Kasparov, and beaten the human champions of “Jeopardy!,” but it had come up short against Harish Natarajan.
But, when I watched the debate a second time, and then a third, I noticed that Natarajan had never really rebutted Project Debater’s basic argument, that preschool subsidies would pay for themselves and produce safer and more prosperous societies. When he tried to, he could be off the cuff to the point of ridiculousness: at one point, Natarajan argued that preschool could be “actively harmful” because it could force a preschooler to recognize that his peers were smarter than he was, which would cause “huge psychological damage.” By the end of my third viewing, it seemed to me that man and machine were not so much competing as demonstrating different ways of arguing. Project Debater was arguing about preschool. Natarajan was doing something at once more abstract and recognizable, because we see it all the time in Washington, and on the cable networks and in everyday life. He was making an argument about the nature of debate.