scientific progress, natural philosophy of the Late Medieval Period is seen as playing the role of apologetics. For philosophers of science, with their repudiation of metaphysics, the task of providing a rational reconstruction of how scientific progress has occurred is nigh on impossible. Even explanations such as the Popperian and the Kuhnian strain under great difficulty and provide only partly satisfactory results. In his “Logik der Forschung” (1934) Karl Raimund Popper argues that metaphysics plays an accidental part in the emergence (...) of new scientific ideas. Correspondingly, in “Structure of Scientific Revolutions” (1962), by carrying out theoretical interpretations and classification of empirical facts without their metaphysical premises, Thomas Kuhn comes to the conclusion that natural science was formed under the influence of erroneous interpretations of Aristotelian natural philosophy presented by medieval natural philosophers. These are some of the reasons why medievalists are still made to defend late medieval natural philosophy from shallow convictions that at medieval universities nothing of any significance to contemporary science and philosophy took place at all. Seeking to render a fragment of a coherent reconstruction of the development of natural philosophy, I will investigate one idea of late medieval philosophy – the explanation of motion (impetus). The main statement of the paper holds that the ideas of late medieval natural philosophy have a decisive significance for the development of modern natural science instead of accidental or negative one. In the paper, following Aristotelian philosophical approach, premises of Jean Buridan’s theory of impetus will be exposed. Then, debates over the explanation of projectile motion are going to be presented, and finally, the necessary significance of this metaphysical idea on the modifications of natural philosophy is going to be ascertained. (shrink)