Yet both men dug in. Each declared his faith in science and the undisputed primacy of facts. And each continued to miss the value of the other’s ideas. Ehrlich was wrong about the apocalypse, but right on aspects of environmental degradation. Simon was right about the influence of human ingenuity on food and energy supplies, but wrong in claiming that improvements in air and water quality validated his theories. Ironically, those improvements were bolstered through regulations pressed by Ehrlich and others.

Ideally, intellectual sparring partners “hone each other’s arguments so that they are sharper and better,” the Yale historian Paul Sabin wrote in The Bet. “The opposite happened with Paul Ehrlich and Julian Simon.” As each man amassed more information for his own view, each became more dogmatic, and the inadequacies in his model of the world grew ever more stark.

The pattern is by now familiar. In the 30 years since Ehrlich sent Simon a check, the track record of expert forecasters—in science, in economics, in politics—is as dismal as ever. In business, esteemed (and lavishly compensated) forecasters routinely are wildly wrong in their predictions of everything from the next stock-market correction to the next housing boom. Reliable insight into the future is possible, however. It just requires a style of thinking that’s uncommon among experts who are certain that their deep knowledge has granted them a special grasp of what is to come.