What does it mean to be alive? The slow contortion of a plant towards light, the spear-flight of a hawk towards their quarry - these are purposeful actions. But where does that purpose come from, and what does it tell us about who we are?In Alive, researcher and natural philosopher Melanie Challenger takes us through the latest discoveries in biology and physics to reveal a radical truth: to be alive is first and foremost a way of being a body. From Greenland sharks that can live for half a millennium, to birds that sense the Earth's magnetic field through their retinas, and even slime moulds that solve mazes, this book tells a new story of intelligence in the living world.A scientifically grounded challenge to the idea that life is either a machine run by genes or an essence separable from the body, Alive restores agency, purpose and meaning to organisms in an age of artificial intelligence and biodiversity loss. By recognising that our bodies are both how and why we are alive, this book asks what it would mean to live - and to act - with that knowledge.