  Other scholars see things differently. John Schuster (1980) finds that the epistemology of the Rules lasted into the 1630s and was superseded (unhappily, in his view) only by the metaphysical quest for certainty of the Meditations. Daniel Garber (1992, 48) also holds that Descartes abandoned his early method after the Discourse. Machamer and McGuire (2006) believe that Descartes expected natural philosophy to meet the standard of absolute certainty through the time of the Meditations, and that he in effect admitted defeat on that score in the final articles of the Principles, adopting a lower standard of certainty for his particular hypotheses (such as the explanation of magnetism by corkscrew-shaped particles). They see the Principles as marking Descartes' “epistemic  turn” away from the methodological stance of realism found in the Rules, Discourse, and Meditations.