What motivates altruism? How essential is the phenomenon of altruism to the human experience? Is altruism readily accessible to the ordinary person? In The Altruistic Species, Andrew Michael Flescher and Daniel L. Worthen explore these questions through the lenses of four disciplinary perspectives biology, psychology, philosophy, and religion. In the course of their investigation, they make an extended argument for the existence of altruism against competing theories that construe all ostensible cases of benevolence as self-interest in disguise. The authors consider theories of...