The chapter sketches a broad picture of some ideas, antecedent to Aristotle’s work, about the origin and development of living beings. Against the background of the new cosmological and metaphysical framework of Aristotle’s biological enterprise, it emphasizes what distinguishes Aristotle from the Presocratics and Plato: his rejection of a shared causal story that would account for both the origin of the universe and the birth of animals and plants. This shift helps to make intelligible Aristotle’s rejection of hylozoism and of the opposite view that life arises, mysteriously, from inanimate material ingredients. To demonstrate that Aristotle discusses the biological views of his predecessors without directly using them to build his own theory, the chapter first turns to Presocratic fragments, mostly of Anaximander and Empedocles, which connect biological matters and cosmogony. Second, the chapter takes a fresh look at how Plato reshapes this connection in his Timaeus, offering a new account of the nature of the universe and the nature of human beings. This account then enables us to evaluate, in the chapter’s final section, the changes that Aristotle brings to the study of living beings, including his rejection of the notion of the latter’s progressive formation.