An important thing to remember about the early years of the Reformation is that it wasn’t necessarily a unified movement. It hadn’t split yet into different “confessional” groups like the ones that survive today. Differences between Lutheranism, Anglicanism, and the Reformed took time to emerge, even though they all shared some common disputes with the medieval church. It took several years for these groups to articulate how they disagreed with each other.

One such moment in which disagreement was realized occurred before John Calvin emerged as a leader of the Swiss Reformation. In 1529, Martin Luther and some of the Swiss reformers gathered at Marburg to discuss some points of agreement and disagreement. Leading up to the debate, Luther and Ulrich Zwingli (1484–1531) had jointly opposed the church’s abuses and errors before the Reformation. But there remained a disagreement between them about the Lord’s Supper.

The roots of the debate reach back to some of the more radical elements of the Reformation that believed Luther hadn’t gone far enough in trying to reform both the teaching and the practice of the church. Even though Luther’s insight into the nature of justification by faith involved a radical break from the usual way of teaching reconciliation with God, Luther was hesitant to mandate worship reforms. Though he removed questionable elements of the mass that had accumulated over time – especially concerning the mass as a sacrifice – the structure of the liturgy remained largely the same. But some thought Luther didn’t go far enough. Luther’s friend and colleague Andreas Karlstadt (1486–1541), for example, instituted radical, but short-lived, reforms of worship in Wittenberg in 1521–1522 while Luther was exiled at Wartburg Castle. Karlstadt and Luther would soon part ways, but his impatience with Luther’s traditionalism marked the beginning of a rift within the Reformation between Luther and the radicals.

In early 1525, Luther published Against the Heavenly Prophets, a treatise in which he responded to some of the radical reformers’ spiritualizing views on the issue of Christian art and the sacraments. Luther’s position was that images, vestments, and the other trappings of the mass could be retained as long as they were helpful and consistent with the gospel. Likewise, Luther contended the biblical sacraments must be taught according to the Lord’s institution for the sake of the comfort of Christians.

Not everyone went so far as the radical reformers on issues of worship. But not everyone agreed with Luther, either. His signature insight on the sacraments was that God’s word of promise doesn’t just symbolize an absent reality but that it gives and bestows God’s real favor. The words of absolution actually give the forgiveness of sin. The waters of baptism have the promise of death and resurrection attached to them. Jesus declares the bread and wine of the Lord’s Supper are his body and blood given and shed for you to eat and drink. Faith is what holds onto these promises from God. But we know they apply to us because they’re physical and tangible. Luther made the case for Christ’s promised presence in the bread and wine across many sermons and treatises on the Lord’s Supper in 1527 and 1528.

Luther's signature insight on the sacraments was that God’s word of promise doesn’t just symbolize an absent reality but that it gives and bestows God’s real favor.

But Zwingli had a number of intellectual roadblocks in the way of accepting Luther’s view of the Lord’s Supper. One had to do with his view of scripture. Like many Renaissance humanists, Zwingli believed scripture was very important, but that it was still an ambiguous book that required spiritualizing and allegorizing. So for Zwingli, “this is my body” actually means “this represents my body.” Another obstacle for Zwingli is that he didn’t believe the risen Christ could be in more than one place at one time. If Jesus is at the right hand of the Father in heaven, then how can he be present in bread and wine on altars all over the world simultaneously? For Zwingli, the bread and wine represent Christ’s body and blood and assist the believer in sharing in spiritual communion with him. But the elements are merely symbolic, in his view.

So the meeting at Marburg was convened in October of 1529 to settle the issue between Luther and Zwingli. Previously, Luther had been unwilling to have it out with Zwingli in person. But it became clear by this point, in the run up to the Diet of Augsburg in 1530, that the Reformation needed to get its house in order. The reformers considered themselves faithful Catholics who needed to clarify their confession to the rest of the church about the truth of the gospel. Fourteen issues brought up at the meeting were agreed upon by Luther and Zwingli. The fifteenth – the matter of Christ’s real presence – was the only one about which they couldn’t achieve agreement.

The difference is whether the sacrament is a benefit or a judgment.

This result has been hotly contested ever since. Though later Reformed theologians like Calvin partially modified Zwingli’s symbolic view of the Lord’s Supper, the Colloquy formalized a difference of confession between Lutherans and the Reformed about the real presence that survives to this day. Since then, Lutherans have confessed that Christ’s body and blood are truly present in the bread and wine such that both believers and unbelievers receive him truly by the mouth. The difference is whether the sacrament is a benefit or a judgment. Lutherans have always wanted to maintain the objectivity of Christ’s presence. Jesus gives his body and blood in the bread and wine regardless of whether I have faith or not because it’s his word of promise that makes him present, not anything that I do. For the Reformed, following after Zwingli and Calvin, the body and blood of Christ are absent from the Supper – even though they’ll insist that one communes spiritually with Christ at the table. And so the debate continues to this day between these two Reformation traditions.

(For more on the Marburg Colloquy, the best resource is Hermann Sasse’s This is My Body: Luther’s Contention for the Real Presence in the Sacrament of the Altar.