Stanford, Calif.

Thomas Sowell is sitting in my chair. He’d driven in to Stanford University from his home 50 miles away, and since he’s 86 years old, the least I could do was to let him choose between the two seats in my office. So he parks behind my desk on the lovely chair that swivels, and I face him, hunched and immobile, on the other side—a fitting way to interview one of America’s great sages.

This...