 One interpretation that has relatively recently emerged addresses the concern over the alleged similarity between innate and adventitious ideas by emphasizing the role that innate ideas play (Nolan 1997, Lennon 2007, Nelson 2008, De Rosa 2010). Consider, for example, the adventitious or sensory idea of the Sun. This idea presents the Sun to the mind as a shaped thing. An analysis of this idea reveals that the innate idea of extension (body) is in play, for without it the human mind simply could not experience (or even conceive) the Sun as shaped. Shape presupposes extension. As Descartes puts it in the Principles, everything “which can be attributed to body presupposes extension, and is merely a mode of an extended thing,” which, according to Descartes, is aligned with the view that “…shape is unintelligible except in an extended thing…” (AT VIIIA 25; CSM I 210). In this sense, insofar as a shaped thing is made intelligible to a human mind, the innate idea of extension is involved. As some scholars have put it, the innate idea underlies or informs the occurring idea of the Sun (Nolan 1997, Nelson 2008, De Rosa 2010). This interpretation finds further support in what Descartes says in a letter to Princess Elisabeth, dated 21 May 1643, where Descartes introduces what he calls the “primitive notions.” These are what in other contexts he calls the innate ideas. In the letter, he claims that these ideas serve as “…the patterns on the basis of which we form all our other conceptions” (AT III 665; CSMK III 218). So, it is the unique role of the innate ideas that distinguishes them from adventitious ideas, where their role is to serve as that which makes other things intelligible. 