The book contains a new critical edition of the Greek text of Aristotle's De Motu Animalium and an English translation of the new text by Benjamin Morison, preceded by an introduction by Christof Rapp and Oliver Primavesi. The introduction comes in two parts: (i) a philosophical introduction by Christof Rapp that aims at drawing a kind of balance of more than three decades of scholarly debate on our treatise and related issues since the publication of Martha Nussbaum's edition and commentary in 1978; (ii) a textual introduction by Oliver Primavesi that sums up the history of textual research on the transmission of De Motu Animalium up to and including the discovery of a new branch of transmission.