According to common belief, the Protestant Reformation began five hundred years ago when, on October 31, 1517, Martin Luther nailed a list of ninety-five theses to the cathedral church door in Wittenberg, Germany. This is a somewhat artificial date, as the Protestant Reformation was a long process begun a century earlier by Bohemian priest John Hus and, at least according to many Protestants, is ever ongoing. “Reformed and always reforming” was the motto of many of the Reformation’s leaders and remains a crucial ideal and challenge today.

What many contemporary Christians do not realize is that the Catholic Church of Rome also underwent a reformation in the sixteenth century and also affirms that the church of Jesus Christ on earth must always be open to reformation. Vatican II (1962–1965) is often considered by both Catholics and Protestants a reforming church council.

However, the church of Jesus Christ on earth remains divided. It has three main branches: Eastern Orthodoxy, Roman Catholicism, and Protestantism. Squeezed in between those three branches are several hybrid denominations.

Protestantism is also divided; there exist in the United States alone at least two hundred Protestant denominations, including The United Methodist Church and its several offshoots. All affirm something neither Eastern Orthodoxy nor Roman Catholicism affirms: that having a reconciled relationship with God, being “justified,” depends solely on God’s grace received through faith and not at all on good works. All Protestants also agree, contrary to Orthodoxy and Catholicism, that all religious tradition must be judged by scripture alone even though tradition, reason, and experience can play a role in settling doctrinal disputes. Finally, all Protestants agree, contrary to Orthodoxy and Catholicism, that every true Christian is a priest who can go directly to God in prayer for forgiveness and never needs a human mediator between herself and God other than Jesus Christ.

These universal Protestant beliefs take on different interpretations and forms, but they are the crucial doctrines of the Protestant Reformation that still divide Christ’s church on earth. Protestants, in spite of other differences among themselves, affirm these doctrines, while Eastern Orthodox and Roman Catholic theologians and leaders deny them.

Tremendous progress toward mutual understanding and even acceptance as equally Christian has been made in the last several decades through intense dialogues between the three major branches of Christianity. But for every two steps forward toward unity, one and a half are taken backward.

Some European and American Lutheran and Catholic bishops and theologians have decided that the doctrine of justification (reconciliation with God) no longer divides their branches of Christianity. And yet, Pope Benedict XVI declared that Protestant churches are not really “churches” but “ecclesial communities.” And nowhere are Catholics permitted by the Catholic hierarchy to partake in Protestant celebrations of the Lord’s Supper, nor are Protestants permitted to partake in Catholic celebrations of the Eucharist (the Catholic term for it). Many Protestant churches, however, welcome any Christian of any denomination, including the Catholic Church, to partake of the Lord’s Supper.

Many Christians consider theological differences unimportant and rush to conclude that the schism between Protestants and Catholics, to say nothing of schisms among Protestants, are scandalous and should be dropped. The charismatic movement of the 1960s and 1970s did much to unite Catholics and Protestants spiritually, but theological differences still remain and matter. The saying that “doctrine divides; Jesus unites” may be true, but where the gospel itself is at stake, division must remain. Luther declared to those who would rush to unity by papering over doctrinal differences: “Unity if possible, but truth at any cost.”

John Wesley, who helped lead a kind of “second Reformation” centuries after Hus and Luther, sought fervently for Christian unity. Some of his followers like to quote him as saying, “If your heart is as mine [i.e., warmed by God], give me your hand.” And yet his open disagreement with fellow Methodist George Whitefield over predestination reveals that he cared deeply about truth and was not willing to sacrifice it on the altar of unity.

So what truth still matters so much that the Reformation of the sixteenth century is still relevant? Two concepts stand out as especially crucial for justifying the continuing divide. The first one is “faith alone.” The gospel itself stands or falls with the belief that, in the words of a famous Protestant hymn, “nothing in my hands I bring; only to thy cross I cling.” In other words, our reconciliation with God depends on nothing but God’s grace received through faith in the sacrifice of Jesus Christ on the cross for us. The second one is “merit,” which the Catholic Church still officially believes is a condition of receiving justifying grace. To Protestant ears, anyway, this concept will always stand in the way of real unity.