The period from Thomas Aquinas to Duns Scotus is one of the richest in the history of Christian theology. The Metaphysics of the Incarnation aims to provide a thorough examination of the doctrine in this era, making explicit its philosophical and theological foundations. Medieval theologians believed that there were good reasons for supposing that Christ's human nature was an individual. In the light of this, Part 1 discusses how the various thinkers held that an individual nature could be united to a divine person. Part 2 shows how one divine person could be incarnate without any other. Part 3 deals with questions of Christological predication, and Part 4 shows how an individual nature is to be distinguished from a person. The work begins with a full account of the metaphysics presupposed in the medieval accounts, and concludes with observations relating medieval accounts to modern Christology.