For centuries, the egoism-altruism debate has echoed through Western thought. Egoism says that the motivation for everything we do, including our seemingly selfless acts of care for others, is to gain one or another self-benefit. Altruism, while not denying the force of self-interest, says that under certain circumstances we can care for others for their sakes, not our own. Over the past half-century, social psychologists have turned to laboratory experiments on humans to provide a scientific resolution of this debate about our nature. The experiments have focused on the possibility that empathic concern-other-oriented emotion elicited by and congruent with the perceived welfare of someone in need-produces altruistic motivation to remove that need. With carefully constructed experimental designs, these scientists have tested the nature of the motivation produced by empathic concern, determining whether it is egoistic or altruistic and, thereby, providing an answer to a fundamental question about what makes us tick. Framed as a detective story, this book traces the scientific search for altruism through numerous studies and attempts to examine various motivational suspects, reaching the improbable conclusion that empathy-induced altruism is indeed part of our nature. The book then considers the implications of this conclusion both for our understanding of who we are as humans (the bad news as well as the good) and for how we might create a more humane society.