Thomas Sowell turned 85 years old this summer, which means he has been teaching economics to Americans through his books and articles for some four decades. So it seems like a natural question: Have we learned anything? Has the level of economic thinking in political debate gone up at all?

“No—in fact, I’m tempted to think it’s gone down,” Mr. Sowell says, without much hesitation. “At one time you had a lot of people who hadn’t had any economics saying foolish things. Now you have well-known economists saying foolish things.”

The paradox is that serious economic discussion enjoys a wider platform than ever before. One of the great bounties of the Internet is the trove of archival news and debate footage that has been dumped onto YouTube and other websites. Anyone with a modem can now watch F.A. Hayek discussing, in a soft and dignified German accent, the rule of law with Robert Bork in 1978. Or Milton Friedman at Cornell the same year, arguing matter-of-factly about colonialism with a young man in a beard, sunglasses and floppy sideways hat.