Octopuses evolved intelligence separately from vertebrates, making them the closest thing to alien minds that we can study on Earth. Philosopher Peter Godfrey-Smith, who has spent years diving with octopuses in Australia, explores what their cognition reveals about the nature of mind. Their nervous systems are radically decentralized, with neurons distributed throughout their arms as well as concentrated in their brains. They can change color and texture instantaneously, communicate through visual displays, and solve problems in captivity that suggest genuine curiosity. Godfrey-Smith traces the evolutionary divergence between cephalopods and vertebrates back more than five hundred million years, to a common ancestor that was probably a simple worm-like creature. Since then, both lineages evolved complex nervous systems independently, an example of convergent evolution that raises questions about what intelligence requires. The book describes Godfrey-Smith's diving experiences in Sydney's Octopolis, a site where octopuses gather in unusual density, displaying social behaviors not typically seen in solitary animals. He reflects on consciousness, sentience, and what it would mean for an octopus to have subjective experience. The writing is clear and personal, grounded in scientific research while remaining accessible. Readers interested in animal cognition, philosophy of mind, or simply the strangeness of the living world will find this book a thoughtful exploration of minds unlike our own.