Around 553 Philoponus made some theological contributions to the Council of Constantinople concerning Christology. His doctrine on Christ's duality, according to which in Christ remain two united substances, united but divided, is analogous to the union of the soul and body in human beings and coincides with the miaphysite school of thought. He also produced writings on the Trinity around this time. Arbiter, John Philoponus' Christological "opus magnum" stands in the line with Cyril of Alexandria and Severus of Antioch. Philoponus asserted the understanding of Christ as divine and human, in opposition to Chalcedonian authors who strove to reach a middle ground.