Who Was Mahakashyapa and His Role

In this episode I read and reflect on Chapter One of Keizan's Denkoroku: Record of the Transmission of Illumination. In it, Shakyamuni Buddha holds up a flower and blinks. Keizan says, "No one knew his intention, and they were silent." Then Mahakashyapa gives a slight smile, and the Buddha acknowledges him as his Dharma heir. What is going on in this koan? Keizan challenges our ideas about awakening, time, causation, and the nature of self.