 Descartes’ challenge, then, is to show that God’s nature is a TIN and that the natures of an “existent lion” and “the maximally perfect island” are not TINs. In the Fifth Meditation Descartes maintains that TINs are different from fictitious ideas in that TINs are in some sense independent of the thought of their conceivers. For example, the nature of a triangle is a TIN because it contains properties that we don’t grasp when we first form the idea of a triangle, and deducing these further properties is a process “more like discovery than creation”. God’s nature also has this feature—we obviously don’t grasp all of the properties of the maximally perfect being when we first form an idea of it. The problem, however, is that it is not clear how this criterion would rule out the natures of a most perfect island or an existent lion as TINs, since in those cases we also don’t grasp all of the properties when we first form the idea. 