The “Greater Magadha” hypothesis calls attention to the decisive role of the urbanizing eastern Ganges valley in the religious history of ancient India. We find there the encounter of two distinct cultures: the Vedic (with its focus on worldly success and rewards in the afterlife) and the Magadhan (with its ideas of karma and rebirth, and its ascetic orders). The Brahmins’ response to this encounter was to adapt and appropriate new ideas and practices. Here, I clarify certain key aspects of how this adaptation proceeded, giving rise in fact to something one can call ‘Brahmanism’, and I offer a fuller explanation of what made that adaptation so successful and durable over time.