By the close of the fourth century, the early Church had agreed that God the Son, the second person of the Trinity, is no less divine than God the Father. But this Trinitarian settlement led directly to another, equally vexing question: how could Jesus of Nazareth, a human man, also be identical to God the Son? After another period of intense debate, the Church defined the doctrine of the Incarnation, which asserts that Christ is one person (or one hypostasis) who exists in two natures, one fully human, the other fully divine (Tanner 1990: 83; Kelly 1978: 338–343). Yet, as with the doctrine of the Trinity, on its own, this conciliar terminology does not attempt to solve the underlying philosophical problem.