Paul Solman: More excerpts today from an interview I did with economist Paul Samuelson nearly a decade ago. Today, his thoughts on whether economics is a science and where math fits in the discipline.

In 1932, when he had not yet finished high school, a 16-year-old Paul A. Samuelson wandered into a college lecture on overpopulation and scarcity. He was instantly enthralled by the language of ...