  Besides logic, natural philosophy is the other field in which Buridan has enjoyed some recognition. This is largely due to the efforts of the pioneering historians of science Pierre Duhem and Anneliese Maier, who saw that Buridan played a key role in the demise of the Aristotelian view of the  cosmos.[49]  Buridan's major contribution here was to develop and popularize the theory of impetus, or impressed force, to explain projectile motion. Rejecting the discredited Aristotelian idea of antiperistasis, according to which the tendency of a thrown projectile to continue moving is due to a proximate but external moving cause (such as the air surrounding  it),[50]  he argues that only an internal motive force, transmitted from the mover to the projectile, could explain its continued motion. The theory of impetus probably did not originate with  Buridan,[51]  but his account appears to be unique in that he entertains the possibility that it might not be self-dissipating: “after leaving the arm of the thrower, the projectile would be moved by an impetus given to it by the thrower,” he says, “and would continue to be moved as long as the impetus remained stronger than the resistance, and would be of infinite duration were it not diminished and corrupted by a contrary force resisting it or by something inclining it to a contrary motion” (QM XII.9: 73ra). He also contends that impetus is a variable quality whose force is determined by the speed and quantity of the matter in the subject, so that the acceleration of a falling body can be understood in terms of its gradual accumulation of units of impetus. But despite its revolutionary implications, Buridan did not use the concept of impetus to transform the science of mechanics. He was not, as Duhem argued, a forerunner of Galileo. He remained unapologetically Aristotelian in too many other respects, continuing to hold that motion and rest are contrary states of bodies and that the world is finite in extent. Buridan seems to have been a philosopher who, though well aware of the shortcomings of the Aristotelian natural philosophy, tried to reshape as much of it as he could in the face of a rapidly mechanizing  worldview.[52]  His revolution was in the details. The big, decisive break was left to his successors.