Zagano traces the historical development of the Eastern Catholic Churches, explaining how each fits in with the broader, universal Church. "We often recite four words which signify our belief in the Unity of the Church: one, holy, Catholic and apostolic every time we say the Nicene Creed at Sunday Mass," Zagano writes. "The words refer to our Church's unity, its sanctified and sanctifying nature, its universality, and its relation to the Twelve Apostles."