Abstract
In his natural philosophy, John Buridan reinterprets Aristotelian conceptions of necessity using a framework derived from his logical writings. After a discussion of Buridan’s account of varieties of necessity, in this paper I shall approach some interpretative uses of that account where two natural philosophical concerns are involved. The first is connected with the relationship of modality and time in a question from the first book of his commentary to De Generatione et Corruptione addressing a consequence from possibilities of alteration to possibilities of generation. The content of that question hinges on the metaphysical connection between alteration and substantial changes. In the third section, I shall explore a quasi-definition of causal necessity and contingency Buridan discusses in the second book of his commentary to the Physics. Buridan’s discussion of alternative descriptions of causal necessity and contingency in that context reveals competing pictures of the role of essences in causal explanation associated with Avicenna and Averroes respectively.