"Causa unionis, causa fidei, causa reformationis in capite et membris"

"Causa unionis, causa fidei, causa reformationis in capite et membris" On the occasion of the 600th anniversary of the Council of Constance, the staff of the Institute of History of the University of Debrecen organized a scientific conference between November 5-7, 2014. Our present volume contains the written version of the majority of the lectures given there. However, due to the extremely tight settlement deadline of the application funds that made it possible to organize the conference, some lectures were unfortunately left out of the volume, as their written versions were not prepared or were prepared late. However, this sadness is perhaps offset by the fact that a volume containing such a large number of studies has never been prepared, just a few weeks after the conference. We would like to thank all the speakers and authors for being cooperative partners in this extremely fast work.