Does the earth’s finite carrying capacity mean economic growth has to stop? That momentous question is the subject of Charles Mann’s brilliant book “The Wizard and the Prophet.” The author portrays two very different approaches. The Prophets say “yes” to the momentous question: They warn, as one wrote in the 1940s, that “only dramatic reductions in human fertility and economic activity will prevent a worldwide calamity.” The Wizards say “no” to the question. They point to scientific innovation that continually does more with less to expand carrying capacity, such as the famous Green Revolution that has raised yields...