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.