During the 1630s Descartes recognized that he could not expect all legitimate claims in natural science to meet the standard of absolute certainty. The realization resulted from a change in his physics, which itself arose not through methodological reflections, but through developments in his substantive metaphysical doctrines. Descartes discovered the metaphysical foundations of his physics in 1629-30; as a consequence, the style of explanation employed in his physical writings changed. His early methodological conceptions, as preserved in the Rules and sketched (...) in Part Two of the Discourse, pertained primarily to his early work in optics. By the early 1630s, Descartes was concerned with new methodological problems pertaining to the postulation of micro-mechanisms. Recognition of the need to employ a method of hypothesis led him to lower the standard of certainty required of particular explanations in his mature physics. (shrink)

This article thinks about changes in the conception of hypothesis during the early modern period. It explains that during this period there was an urgency to redefine human knowledge so that uncertainty became one of its inevitable and acceptable features, and certainty was replaced by probability as an adequate achievement in knowledge of the natural world. It discusses Isaac Newton's deep-seated rejection of hypotheses and the assumption that their use in natural philosophy would compromise its status as genuine scientific knowledge.