On October 1, 1529, Martin Luther, representing German Lutherans, and Huldrych Zwingli, on behalf of the Swiss Reformed churches, met with the intent of brokering an alliance between their two movements. This series of conversations subsequently became known as the Colloquy of Marburg, after the German town in which the summit was held. Across four days of debate, the two reformers came to agreement on fourteen points but found consensus impossible to reach on a fifteenth disputed issue: the nature of the Eucharist. Discussions broke down, and despite later attempts to find common ground, the disagreements aired at Marburg have continued to divide the Lutheran and Reformed movements in the five centuries since.

Like nuclear fission, church splits often produce huge amounts of energy – but at a high cost. What about fusion?