 Rejection of a permanent agent eventually led to the philosophical problems of the seeming continuity of mind and also of explaining how rebirth and karma continue to be relevant doctrines without an eternal mind. This challenge was met by the Theravāda school by introducing the concept of mind as a factor of existence. This "life-stream" (Bhavanga-sota) is an undercurrent forming the condition of being. The continuity of a karmic "person" is therefore assured in the form of a mindstream (citta-santana), a series of flowing mental moments arising from the subliminal life-continuum mind (Bhavanga-citta), mental content, and attention.
