The roles of each deity were fluid, and each god could expand its nature to take on new characteristics. As a result, gods' roles are difficult to categorize or define. Despite this flexibility, the gods had limited abilities and spheres of influence. Not even the creator god could reach beyond the boundaries of the cosmos that he created, and even Isis, though she was said to be the cleverest of the gods, was not omniscient. Richard H. Wilkinson, however, argues that some texts from the late New Kingdom suggest that as beliefs about the god Amun evolved he was thought to approach omniscience and omnipresence, and to transcend the limits of the world in a way that other deities did not.