Hun and po are types of souls in Chinese philosophy and traditional religion. Within this ancient soul dualism tradition, every living human has both a hun spiritual, ethereal, yang soul which leaves the body after death, and also a po corporeal, substantive, yin soul which remains with the corpse of the deceased. Some controversy exists over the number of souls in a person; for instance, one of the traditions within Daoism proposes a soul structure of sanhunqipo 三魂七魄; that is, "three hun and seven po". The historian Yü Ying-shih  describes hun and po as "two pivotal concepts that have been, and remain today, the key to understanding Chinese views of the human soul and the afterlife."