Xperiment is the fourth book in the Royal Fireworks philosophy curriculum. It features a boy named X who becomes involved with a group of children who struggle to find the meaning of justice in the small society that they have created for themselves. The kids explore the philosophical concepts of selective rule-breaking, thought-experimenting, and proposing alternative theories. The story introduces philosophies about human nature, civilization, and government by such philosophers as Plato, Aristotle, Rousseau, Locke, Hobbes, and Hume. Children are introduced to these concepts in an interesting and engaging way that makes them accessible and that highlights them as real-world issues.