Theo Rising is the second book in the Royal Fireworks philosophy curriculum. It features a young girl named Theo who learns about various theories posed by the earliest Greek philosophers, the Presocratics, who asked about the nature of the world around them and deliberated on an essential building block for everything in the universe. Theo learns about the concepts of earth, water, air, fire, and numbers as the ultimate source of everything else, and she discovers different criteria with which to judge between the competing theories. Children are introduced to these philosophical concepts in a fun, creative, innovative way that makes them accessible, even to the very young.