  Moreover, the Cartesian criterion is irrelevant to judging cases of empirical knowledge, Gassendi suggests—and even if this criterion were not irrelevant, Descartes's own claims to knowledge should fail all the same. First, in the case of empirical knowledge, Gassendi proposes that the Cartesian criterion fails on classical Skeptical grounds: it is possible for us to have ideas from the senses we take to be clear and distinct which are nevertheless not the basis for warranted claims to empirical knowledge of a general nature. Though we may have clear and distinct ideas about the appearances of, for example, the color of the sky we perceive, we cannot infer from this clarity and distinctness that we know what color the sky is. As the Skeptics warn, the sky could appear to different persons in different colors, and as Gassendi adds, our ideas of such an appearance could each be clear and distinct (O III (DM) 314b; R 198-199). Second, knowledge claims Descartes takes to be demonstrated by reason alone Gassendi dismisses as anyway failing the proposed criterion; they are partial and confused, he suggests, because they lack the immediacy characteristic of judgments we attain by strictly empirical means.  Whereas ideas we gain from the senses directly represent worldly objects and events, ideas we attain by deductive proof are but hypothetical analogues to such sensory-derived ideas: