What is life? For generations, scientists have struggled to make sense of this fundamental question, for life really does look like magic: even a humble bacterium accomplishes things so dazzling that no human engineer can match it. Huge advances in molecular biology over the past few decades have served only to deepen the mystery. In this penetrating and wide-ranging book, world-renowned physicist and science communicator Paul Davies searches for answers in a field so new and fast-moving that it lacks a name; it is a domain where biology, computing, logic, chemistry, quantum physics, and nanotechnology intersect. At the heart of these diverse fields, Davies explains, is the concept of information: a quantity which has the power to unify biology with physics, transform technology and medicine, and force us to fundamentally reconsider what it means to be alive—even illuminating the age-old question of whether we are alone in the universe. From life’s murky origins to the microscopic engines that run the cells of our bodies, The Demon in the Machine journeys across an astounding landscape of cutting-edge science. Weaving together cancer and consciousness, two-headed worms and bird navigation, Davies reveals how biological organisms garner and process information to conjure order out of chaos, opening a window onto the secret of life itself.