Peter Godfrey-Smith’s Other Minds casts a new light on the mind of the octopus, and on our own. Although mammals and birds are regarded as the smartest creatures on Earth, it has lately emerged that a distant branch of the tree of life has also sprouted higher intelligence: the cephalopods, particularly the octopus. Peter, a philosopher of science and a scuba diver, talks to Krissy Kneen about the intelligence of cephalopods and their fascinating evolutionary lineage.