  The challenge posed by the need to account for the continuity of mind in the absence of an enduring, substantive self, was met with mixed  success by early Abhidharma authors. Thus, most Ābhidharmikas  understood mind primarily as a species of mental cognition and, as  such, explained the continuity of the mental stream as a successive  series of cognitive events conditioned by such factors as karmic  formations, appropriation, and mind itself.