  An important, and perhaps unintended, consequence of this project of  reductive analysis is that momentariness is revealed to be not only a principle of the nature of reality, but also (and more significantly) of cognitive awareness itself. In the formula of dependent arising  (quoted above in   §3.3),  the awareness that arises in conjunction with the activity of a given sensory system is itself impermanent and momentary: visual awareness  and visual object, for instance, are both events within a mental  stream of continuing relations. The question that Abhidharma  philosophers must confront is precisely what accounts for the sense  of recollection that accompanies these cognitive series. In other  words, if discrete, episodic cognitive events are all that  constitutes the mental domain, how does appropriation and grasping,  for instance, occur? The causal account, it seems, gives only an  incomplete picture of the mental, for even as the Sanskrit term for  cognitive awareness, vijñāna, conveys the sense of differentiation and discernment, it is not exactly clear how such  discernment also sorts between an inner and an outer domain of  experience. Indeed, consciousness is not merely a faculty for  discerning and sorting through the constitutive elements of  experience, but itself an event in a series of interdependent causes  and conditions. As we shall see below, it is only later with the  development of the Yogācāra notion of reflexive awareness,  that this issue is properly addressed.