Kommission für Glauben und Kirchenverfassung
From 2003 to 2008 he was active in the ecumenical movement through the Faith and Order Commission and has written on issues related to ecumenism. He served as a delegate to the official Reformed/Roman Catholic International Dialogue (2011-2016), where he was instrumental in prompting the World Communion of Reformed Churches (WCRC) to affiliate with the historic "Joint Declaration on Justification" (JDDJ). He contributed to the official WCRC "signing statement" to the JDDJ, as ratified in July 2017, at the 500th anniversary of the Reformation. In the spring semester of 2019 he was a visiting professor of ecumenical theology at the Pontifical Gregorian University in Rome.