 Eriugena’s thought is best understood as a sustained attempt to create a consistent, systematic, Christian Neoplatonism from diverse but primarily Christian sources. Eriugena had a unique gift for identifying the underlying intellectual framework, broadly Neoplatonic but also deeply Christian, assumed by the writers of the Christian East. Drawing especially on Basil, Gregory of Nyssa, Pseudo-Dionysius the Areopagite, Maximus Confessor, as well as on the more familiar authorities (auctores) of the Latin West (e.g., Cicero, Augustine, Macrobius, Martianus Capella, Boethius), he developed a highly original cosmology, where the highest principle, “the immovable self-identical one” (unum et idipsum immobile, Periphyseon, Patrologia Latina 122: 476b), engenders all things and retrieves them back into itself. Contrary to what some earlier commentators supposed, it is most unlikely that Eriugena had direct knowledge of the original texts of Plotinus, Porphyry, Proclus, or other pagan Neoplatonists, but he did have some direct knowledge of Plato (a portion of Timaeus in the translation of Calcidius) as well as familiarity with the pseudo-Augustinian Categoriae decem.