 For Descartes, the sciences are deeply interdependent and interconnected, and they must be learned by means of one method (AT 10: 360–361, CSM 1: 9–10). He defines “science” (scientia) in Rule 2 as “certain and evident cognition” (omnis scientia est cognitio certa et evidens, AT 10: 362, CSM 1: 10). Many scholastic Aristotelians define science in the same way. However, Aristotelians do not believe that every science satisfies this definition equally; some sciences (like mathematics) may be more exact and, therefore, more certain than others (like natural philosophy). Aristotelians consistently make room for what Descartes terms “probable cognition”, especially in natural philosophy (Rule 2, AT 10: 362, CSM 1: 10). In Rule 2, Descartes boldly declares that “we reject all […] merely probable cognition and resolve to believe only what is perfectly known and incapable of being doubted” (ibid.).