Brian Skyrms presents a fascinating exploration of how fundamental signals are to our world. He uses a variety of tools — theories of signaling games, information, evolution, and learning — to investigate how meaning and communication develop. He shows how signaling games themselves evolve, and introduces a new model of learning with invention. The juxtaposition of atomic signals leads to complex signals, as the natural product of gradual process. Signals operate in networks of senders and receivers at all levels of life. Information is transmitted, but it is also processed in various ways. That is how we think — signals run around a very complicated signaling network. Signaling is a key ingredient in the evolution of teamwork, in the human but also in the animal world, even in micro-organisms. Communication and co-ordination of action are different aspects of the flow of information, and are both effected by signals.