What are the motifs in Ender's Game by Orson Scott Card?

Ethics are a recurring idea in the book. Besides the obvious questions related to murder without punishment, moral and ethical questions related to the manipulation of children and the significance of compassion arise throughout Ender's Game. Even though Ender commits murder and receives no punishment, he does feel remorse. It is Ender's ability to empathize, however, that targets him for the role of a mass murderer.