James R. Flynn, one of the most influential figures in modern psychology, isn't a psychologist. He is a trained political philosopher. He broke into psychology in his 50s by painstakingly documenting the now-famous "Flynn effect"—the strong tendency of nations' average measured intelligence ("IQ") to rise over time. "Are We Getting Smarter?" interweaves the author's expertise in psychology, political philosophy and sociology to shed light on a loosely related set of questions about human intelligence. At times the book feels like a collection of essays, but it forms one continuous argument....