Starting from his De haeresibus 46,9-10, the present article examines Augustine’s contention that, among the Manichaeans, there was a certain ceremony in which human semen (i.e., sperma and menstrual fluid) was collected and consumed during a eucharistic rite. My contextual analysis of the pivotal passage, haer. 46,9-10, is followed by an overview of scholarly opinions on this text. From here I proceed to interpret the incriminated rite in light of the Seduction of the Archons myth and conclude that, according to Augustine, the Manichaeans consider the ‘vital substance’ (or ‘light’ or ‘living soul’) in the life of plants, animals and human beings, to be the very nature of God, which should be released whenever possible. I finish my research by interpreting the Manichaean practice within a wider ‘gnostic’ context, in particular Epiphanius’ report on the ‘Borborites’. My final conclusion is that we should try to understand both Manichaeans (like the ‘Catharists’) and Gnostics (like the ‘Borborites’) according to their own logic: both appear to have considered the life-substance of man, i.e., the semen, as divine, and indeed a part of God.