Each instant is a union of myriad, and possibly uncountable, factors. Causes and conditions, choices and preferences, aversions and avoidances all conflate and project a seeming moment, an apparational sense of self and what it ephemerally is experiencing.
Note all the mirage-like words.
This dream-like reality which is so real to our senses, emotions, common mind, and sense of self is the true meditation seed, which is why present-moment Awareness is the focus in this cycle of meditations. “Who” is an ever changing combination, an arising of factors stirred together by the unrecognized myriad factors mentioned above. And, the only way to experience this ever-changing “who” is to notice how changeable it is, how spontaneously arising it is, how costume oriented, too.
But that requires spacious openness which requires shamatha and its union with vipashyana. So, we meditate.