A philosopher dons a wet suit and journeys into the depths of consciousness. Peter Godfrey-Smith is a leading philosopher of science. He is also a scuba diver whose underwater videos of warring octopuses have attracted wide notice. In this book, he brings his parallel careers together to tell a bold new story of how nature became aware of itself. Mammals and birds are widely seen as the smartest creatures on earth. But one other branch of the tree of life has also sprouted surprising intelligence: the cephalopods, consisting of the squid, the cuttlefish, and above all the octopus. New research shows that these marvellous creatures display remarkable gifts. What does it mean that intelligence on Earth has evolved not once but twice? And that the mind of the octopus is nonetheless so different from our own? Combining science and philosophy with first-hand accounts of his cephalopod encounters, Godfrey-Smith shows how primitive organisms bobbing in the ocean began sending signals to each other and how these early forms of communication gave rise to the advanced nervous systems that permit cephalopods to change colours and human beings to speak. By tracing the problem of consciousness back to its roots and comparing the human brain to its most alien and perhaps most remarkable animal relative, Godfrey-Smith's Other Minds sheds new light on one of our most abiding mysteries.