Some of the most difficult questions in relations with the ancient Eastern Churches concern some doctrine (i.e. "Filioque", scholasticism, functional purposes of asceticism, the essence of God, Hesychasm, Fourth Crusade, establishment of the Latin Empire, Uniatism to note but a few) as well as practical matters such as the concrete exercise of the claim to papal primacy and how to ensure that ecclesiastical union would not mean mere absorption of the smaller Churches by the Latin component of the much larger Catholic Church (the most numerous single religious denomination in the world) and the stifling or abandonment of their own rich theological, liturgical and cultural heritage.