  Duhem presented Galilean dynamics as a continuous development out of medieval dynamics. He recovered the late medieval theory of impetus, tracing it from John Philoponus’ criticism of Aristotle to its mature statements in the fourteenth century works of John Buridan and Nicole Oresme: “The role that impetus played in Buridan’s dynamics is exactly the one that Galileo attributed to impeto or momento, Descartes to ‘quantity of motion,’ and Leibniz finally to vis viva. So exact is this correspondence that, in order to exhibit Galileo’s dynamics, Torricelli, in his Lezioni accademiche, often took up Buridan’s reasons and almost his exact words” (1917, 163–62 [EHPS, 194]). Duhem then sketched the extension of impetus theory from terrestrial dynamics to the motions of the heavens and earth: