St. Augustine of Hippo 
The Two Souls of the Manicheans [EPUB ebook] 

During his time with the Manicheans, St. Augustine went into depth regarding their theological suppositions about the nature of the world and the natural mortality of the human soul. As strict dualists, the Manicheans rejected the more familiar Platonic speculation of the soul, insisting on a two-faceted soul. What little is known about Manichean religious thought, which is a defunct world religion, is eloquently described here and in similar texts by St. Augustine.