Book excerpt: One of the great enigmas of humanity is why we have such a devastating capacity for evil as well as such an enormous ability to do good. What makes some people commit violent harm, while others risk their lives to help those they may not even know? Now, to explore and navigate this essential question of human behavior, the editors at TIME bring you the special edition 'The Science of Good and Evil.' You'll examine "The Roots of Good and Evil," and consider the capacity for morality in animals. Then consider "What Makes Us Moral" by looking at the seemingly innate moral compass of human children and the role that nurturing plays in developing it. Follow modern neuroscience deep into the brain to see what it can tell us about where good and evil behavior might reside and what role genuine love plays in their development. Through it all, visit and analyze tales of senseless acts of violence and the profound acts of selflessness that occur in their wake. As destructive technologies and artificial intelligence continue to develop and strengthen, there has never been a more important time to understand the nature of our capacity for good and evil.