For all their notable successes in interfaith cooperation, Roman Catholics and Protestants are still separated by knotty doctrinal differences as old as the Reformation. Among the major problems are varying notions of the Eucharist or Lord's Supper, differing concepts of priesthood and ministry, and conflicting definitions of apostolic succession, that essential tie to the Apostles that most Christians see—in various ways—as a necessary mark of an authentic church. By Catholic standards, neither the ministry nor the Eucharist of Protestant churches is valid, and until recently, any hope of unity seemed to lie in Protestant submission to those standards.
Now, judging from a scattering of articles in theological journals and some quiet meetings among Catholics, Anglicans and Lutherans, a new hope is emerging. The churches, it seems, may yet find enough common theological ground for a mutual recognition of ministries. If they do, it is conceivable that before the end of the decade Catholics could share both pulpits and Communion with Anglicans and Lutherans. This would mark the most significant step toward Christian unity since the start of the ecumenical movement.
Body and Blood. For the past four centuries, Catholic doctrine has depended heavily on the decrees of the Council of Trent, which in the mid-16th century sought to answer the challenge of Protestant reformers by carefully defining—among other issues—the priesthood, the episcopacy, and the seven sacraments recognized by the church. The bishops and theologians at Trent concentrated on a concept of the priest as a man officially set apart to offer sacrifice and on a definition of the Eucharistic celebration—the core of the Catholic Mass—as the same sacrifice, in a different manner, as Christ's sacrifice on the cross. According to the Trent decrees, at the moment of consecration in the Mass, bread and wine undergo "transubstantiation." They become, except in outward appearances, the body and blood of Christ. The sacrament of holy orders, conferred on a priest by a duly consecrated bishop and only by a bishop, give the priest the power to effect this mystical change. The bishops, lineal successors to the first Apostles, received this commission through the Apostles from Christ himself at the Last Supper.
The Protestant reformers radically reinterpreted these doctrines. Both Martin Luther and John Calvin explained the "real presence" of Christ in the Eucharist in different ways. Other reformers declared that the sacrament was merely a commemorative act recalling the Last Supper. In preaching the "priesthood of all believers," Luther acknowledged the need of ministers to preach the Gospel, but nearly all Continental Protestants rejected the necessity of bishops and the notion of holy orders as a sacrament.
The Church of England, while retaining bishops and an ordination ceremony, also played down the sacrificial character of the Eucharist and the sacramental status of the priesthood. In the view of traditional Catholic theology, the Church of England (and other churches of the Anglican communion) thus lost apostolic succession and validity.