Libertarianism is the simple morality we learned as children: Don’t strike first, don’t steal or cheat, keep your promises. If you inadvertently fail to live up to these standards, make it up to the person you’ve harmed. If someone harms you, you may defend yourself as needed to stop the aggressor and obtain reparations. This simple morality works group-to-group just as it works one-to-one to bring about a peaceful and prosperous world.