Against these main tenets of Manichaeism, both John Chrysostom and Augustine spent much of their time writing. Augustine, a former Manichean, wrote with a special sort of passion. Some of this passion became evident in the discourse that Augustine recorded between himself and Faustus, a Manichaean leader. Faustus was highly regarded by other Manicheans and his arguments can rightly be viewed as representative of Manichaeism as a whole. Augustine laid out the words of Faustus that he wished to contend with as “Again, I say, the Christian Church, which consists more of Gentiles than of Jews, can owe nothing to Hebrew witnesses.” The Manicheans argued that since the Christian church consisted of far more Gentiles than Jews and was essentially a Gentile institution, the Jewish prophets and Old Testament were useless. Faustus did still claim to be a Christian and confess Christ, but he denied that the Old Testament even prophesied of Christ. Augustine made clear to Faustus that the orthodox view of Scripture included both the Old and New Testaments and that both the Old and New Testaments spoke of Christ. Augustine turned to Paul in Romans 15:4 for his support of the Old Testament and the prophets and accused Faustus of preaching a gospel contrary to Scripture: “If Faustus denies this [The Old Testament and Prophets], we can only say with Paul, “If any one shall preach to you another doctrine than that ye have received, let him be accursed.”
Augustine in other anti-Manichaean writings exposed the inconsistencies and hypocrisies of Manichaeaism. In Against the Epistle of Manichaeus Augustine displayed Mani’s claim to be the comforter promised by Christ and his denial of the incarnation to be preposterous:
“Besides, you should explain how it is that, while the Father, Son and, Holy Spirit are united in equality of nature, as you also acknowledge, you are not ashamed to speak of Manichaeus [Mani], a man taken into union with Holy Spirit as born of ordinary generation; and yet you shrink from believing that the man taken into union with the only-begotten Wisdom of God was born of a Virgin. If human flesh, if generation [concubitus viri], if the womb of a woman could not contaminate the Holy Spirit, how could the Virgin’s womb contaminate the Wisdom of God?”
Augustine would go on to point out that clearly Mani could not have been the promised Paraclete as the New Testament told of the history of the promise and pouring out of the Holy Spirit as the Paraclete/Comforter.
Augustine and Chrysostom both attacked Manichaeism on the strict dualism and the low regard for physical matter. John Chrysostom especially attacked the Manicheans for their denial of the Biblical creation and view of physical mater. In his sermon on Genesis 1, Chrysostom said, “Even if Mani accosts you saying matter preexisted, or Marcion, or Valentinus, or pagans, tell them directly: ‘In the beginning God made heaven and earth.” In a homily on Matthew 14 (feeding of the five thousand) Chrysostom wrote:
“And why doth He not make it of things that are not? Stopping the mouth of Marcion, and of Manichaeans, who alienate His creation from Him, and teaching by His very works, that even all the things that are seen are His works and creatures, and signifying that it is Himself who gives the fruits, who said at the beginning, ‘Let the earth put forth the herb of grass,’ and ‘Let the waters bring forth things moving with living souls.’”“And why doth He not make it of things that are not? Stopping the mouth of Marcion, and of Manichaeans, who alienate His creation from Him, and teaching by His very works, that even all the things that are seen are His works and creatures, and signifying that it is Himself who gives the fruits, who said at the beginning, ‘Let the earth put forth the herb of grass,’ and ‘Let the waters bring forth things moving with living souls.’”
Chrysostom in this passage accused the Manichaeans of alienating God from the creation. In their strict dualism and insistence on the evil of physical matter they forced the good God to be absolutely removed from His creation. Chrysostom here conjectured that if Jesus had called the food for the five thousand out of nothing, he could have not only definitively proved that he is God, but also Creator. Chrysostom goes on to show that even though Christ did not create the loaves and fish ex nihilo, He still in this miracle showed himself to be Creator and God—thus removing any idea of a God who is separate.
Chrysostom also wrote against specifically Manichaeism for its despising of the physical body: “For the latter [Manichaeans] call the body a treacherous thing, and from the evil principle.” John Chrysostom accused them as “those who assert that the workmanship of God is evil.” Augustine joined Chrysostom in this condemnation. Augustine said concerning evil “sin is not the striving after an evil nature, but the desertion of a better, and so the deed itself is evil, not the nature which the sinner uses amiss.” Here he criticized the Manichaeans as ones who did not understand sin and evil. Corruption caused everything in this world to commit sin and act in an evil way, yet it was not the physical nature that was responsible for sin and everything physical should not be thought of as evil.
Because of their view on physical matter, the Manichaean system had no room for the Incarnation. Augustine and Chrysostom both attacked this aspect of the Manichaean heresy vigorously. Chrysostom wrote in Against the Marcionites and Manichaeans:
“The wicked mouth of the devil speaking through Marcion of Pontus, and Valentinus, and Manichaeus of Persia and many more heretics, has attempted to overthrow the doctrine of the Incarnation and has vented a diabolical utterance declaring that He did not become flesh. . . although the sufferings, the death, the burial, the thirst, cry aloud against this teaching.”
Chrysostom appealed here to the clear testimony of scripture concerning Jesus physical feelings. One who is not incarnate cannot feel thirst, cannot suffer, and most importantly cannot die. Chrysostom saw the importance of denying the Manichaean heresy at this vital point.
Augustine attacked Manichaeanism in a similar fashion in his polemics against Faustus. Faustus confessed that “it is hardly consistent to believe that God, the God of Christians, was born from the womb.” In doing so, Faustus displayed the true Manichaean view of Scripture as uninspired. To validate this denial of the Incarnation Faustus argued that the “Jesus of Matthew is a different person from the Jesus of Mark.” In response to these statements Augustine showed that the incarnate Christ did not lose his Godhead, but the Incarnation was Christs taking on the flesh of men “For in the unchangeable possession of that nature by which in the form of God He is equal to the Father, He took our changeable nature, by which He might be born of a virgin.” In regards to the importance of the Incarnation for salvation, Augustine responded to Faustus with:
“The second man from heaven, heavenly, is the Lord Jesus Christ; for, being the Son of God, He became flesh that He might be a man outwardly, while He remained God within; that He might be both the true Son of God, by whom we were made, and the true Son of man, by whom we are made anew.” 
Augustine and John Chrysostom both took up the defense of the orthodox faith over against the heresy of Manichaean philosophy. Even if Manichaeism presented itself as an alternative form of Christianity and confessed to believe in Jesus Christ, these church fathers recognized it for the heresy that it was. In their defense against Manichaeism they rightly defended the Old Testament scripture, the truth of God as the Creator and the absolutely vital truth of the Incarnation.
 Augustine, Confessions, trans. Henry Chadwick (New York: Oxford University Press, 2008), 77.
 Augustine, Confessions, 77.
 “In the nine years or so during which my vagabond mind listened to the Manichees, I waited with intense yearning for the coming of Faustus.” Augustine’s first encounters with Faustus were during the time of his life when he confessed to be a Manichean. He had his doubts and questions about Manichaeanism but his comrades ensured him that Faustus would be able to answer any question he had. Augustine, Confessions, 77
Augustine, “Reply to Faustus the Manichaean,” in The Writings Against the Manichaeans and Against the Donatists, trans. Richard Stothert. Nicene and Post Nicene Fathers Series 1 ed. Philip Schaff vol. 4 (Grand Rapids: Eerdmans, 1989), 161, 199.
 Augustine, “Reply to Faustus the Manichaean,” 199.
 Augustine, “Reply to Faustus the Manichaean,” 207.
 Augustine, “Against the Epistle of Manichaeus,” in The Writings Against the Manichaeans and Against the Donatists, trans. Richard Stothert, Nicene and Post Nicene Fathers Series 1 ed. Philip Schaff vol. 4 (Grand Rapids: Eerdmans, 1989), 132.
 Augustine, “Against the Epistle of Manichaeus,” 133.
 John Chrysostom, “Homily 2,” in St. John Chrysostom: Homilies on Genesis 1-17, trans. Robert C. Hill, The Fathers of the Church vol. 74 (Washington DC: The Catholic University of America Press, 1986), 34.
 John Chrysostom, “Homily XLIX,” in St. Chrysostom: Homilies on The Gospel of Saint Matthew, trans. George Prevost, Nicene and Post Nicene Fathers Series 1 ed. Philip Schaff vol. 10 (Grand Rapids: Eerdmans, 1989), 295.
 De Wet, “John Chrysostom on Manichaeism,” 2.
 John Chrysostom, “Commentary on Galatians,” in St. Chrysostom: Homilies on the Epistles to the Galatians, Ephesians, Philippians, Colossians, Thessalonians, Timothy, Titus, and Philemon, trans. Gross Alexander, Nicene and Post Nicene Fathers Series 1 ed. Philip Schaff vol. 13 (Grand Rapids: Eerdmans, 1989), 39.
 John Chrysostom, “Commentary on Galatians,” 39.
 Augustine, “Concerning the Nature of Good, Against the Manichaeans,” in The Writings Against the Manichaeans and Against the Donatists, trans. Albert H. Newman, Nicene and Post Nicene Fathers Series 1 ed. Philip Schaff vol. 4 (Grand Rapids: Eerdmans, 1989), 359.
 John Chrysostom, “Against Marcionists and Manichaeans,” in St. Chrysostom: On The Priesthood; Ascetic Treatises; Select Homilies and Letters; Homilies on the Statues, trans. W.R.W. Stephens, Nicene and Post Nicene Fathers Series 1 ed. Philip Schaff vol. 9 (Grand Rapids: Eerdmans, 1989), 205.
 Augustine, “Reply to Faustus the Manichaean,” 159.
 Augustine, “Reply to Faustus the Manichaean,” 159.
 Augustine, “Reply to Faustus the Manichaean,” 161.
 Augustine, “Reply to Faustus the Manichaean,” 157.
By Arend Haveman