The Carolingian philosopher and theologian Johannes Scottus Eriugena is an important point of confluence of many streams of Trinitarian thought, as well as a significant and creative theologian in his own right. Because of his remarkable ability to work back through Patristic sources to the original Neoplatonic doctrine by means of sheer ratiocination, Eriugena also acts a valuable critic of the many streams of Trinitarianism that come through to him, both Eastern and Western. This issue has been well explored from the perspective of the Neoplatonic elements that went up to make it. However, a good deal of new work on the Liberal Arts tradition has appeared recently (including my own). The integration of this work with existing scholarship on the Neoplatonic elements in his Trinitarian theology is an important project, which also has implications for contemporary debates in theology, especially as regards inculturation. In this communication, the issue of Eriugena's methodology will be addressed, and the extent to which that reflects Patristic methodology as a whole, when confronted with an attractive and sophisticated system of thought.