A Very powerful case has been made out for the influence of the Platonism of Plotinus upon Saint Augustine. From the Manichaean simple solution of the problem of evil Augustine was delivered by reading the neo-Platonists and especially Plotinus. It was Plotinus who convinced him that God was a spirit, not a luminous body, and he always remained grateful for this deliverance from the crude fantasies of the Manichaeans. In the two years before his conversion when he was receiving a deeper penetration into Christianity through the sermons of St. Ambrose, he came to know of Plotinus in a very few treatises of the Enneads (certainly I, 6 ‘On the Beautiful’ and quite probably V, 1 ‘On the Three Chief Hypostases’) in the Latin translation of Marius Victorinus. St. Ambrose made a determined effort to apply the principles of Plotinus' philosophy to the clarification of the Christian doctrine of the Trinity as against the Arians. The results of such an attempt might not be theologically satisfying but they are interesting. This impact of the mind of Plotinus upon the mind of Augustine was a decisive one because Augustine found a very great area of agreement between the teaching of Plotinus and that of the Scriptures as expounded by St. Ambrose, above all the Gospel of St. John. It was their agreement that God is spirit and altogether immaterial, as Plotinus explains, which liberated him from the Manichaean materialism. Augustine thought that Plotinus' teaching about the Divine Mind was identical with that of St. John about the Divine Logos.