An economics professor at the University of California, Berkeley, Brad DeLong, calls Russ Roberts the "lyingist economist alive." Mr. Roberts, a professor at George Mason University, defends himself here. Professor Roberts recently sent me a copy of his novel The Price of Everything, and in looking through it before this fight broke out, I was surprised, given Mr. DeLong's left-wing reputation and Mr. Roberts's free-market proclivities, to find that in the "further reading" section of the novel Mr. Roberts writes, "On economic growth, read Brad DeLong's unpublished essay, 'Cornucopia: Increasing Wealth in the Twentieth Century.' It's full of fascinating data and insights into the transformation of our standard of living." Mr. Roberts calls Mr. DeLong's work fascinating and insightful and recommends people read it; Mr. DeLong responds by calling him a liar. Weird, even for academics or economists. They seem to be fighting about climate change, which may explain some of why Mr. DeLong is so hot under the collar.