Real Presence, expression of the belief among certain Christians, especially Roman Catholics and some Anglicans, that the actual presence of the body and blood of Jesus is in the Eucharist. Saints Ignatius of Antioch, Justin Martyr, and Irenaeus wrote of the bread and wine of the Eucharist as the actual body and blood of Christ. In the 4th cent. the focus shifted to the substantial transformation of the elements; by the 7th cent. the idea that the bread and wine were transmuted or converted in substance to the body and blood of Christ was prevalent throughout Christendom. This transformation was the subject of controversy in the 9th and 11th cent., and a Roman Council of 1079 issued a statement declaring that the bread and wine are changed substantially through consecration. The Fourth Lateran Council (1215) again sanctioned belief in transubstantiation. The doctrine recieved its classic formulation in the writing of St. Thomas Aquinas. The Council of Trent, confronted with Protestant challenges, especially from Ulrich Zwingli and John Calvin, issued an authoritative teaching upholding the doctrine of transubstantiation. For Protestant interpretations, see Lord's Supper.