While the West was confronting Pelagianism, both Nestorianism & Monophysitisim rocked the eastern Church during the 5th century. Nestorianism taught that there were two persons in Christ, one human and one divine, while Monophysitism taught that Christ only had one divine nature. In confronting these heresies, the Church definitively formulated the doctrine of the hypostatic union, that Christ is one Divine Person with two natures, human and divine.