Here George Dyson considers the intriguing question of artificial life: the possibility that machines will one day come to life, or are even alive already. Dyson argues that life, having emerged once already through biological evolution, is presently emerging for a second time, on this occasion through the spontaneous evolution of intelligence within our rapidly expanding computer networks. Dyson shows that to a real extent we have created life, but have largely failed to notice. Others have considered this possibility and Dyson guides us through this alternative scientific and literary tradition, recounting the insights of historical figures such as Hobbes, Samuel Butler, Erasmus and Charles Darwin, as well as a variety of researchers from the 20th century.