1. Members of the Chaldean Catholic Church. Those from the Ch. of E. who joined the Roman communion were first called Chaldeans in the brief Benedictus sit Deus of Pope Eugenius IV (1445) in order to distinguish them from ‘Nestorian’ heretics.

2. A term used in modern times for the ethnic group comprising both Chald. Catholics and members of the Assyrian Ch. of E. The idea that E.-Syr. Christians were properly called Chaldeans on account of a historical connection with the ancient people of that name can be found in 19th-cent. books by W. Ainsworth, A. H. Layard, and Hormuzd Rassam. This idea was taken up by P. Nasri (1905) and Addai Scher (1912) and then by other nationalistic writers from the Chaldean church who wanted an alternative to the Assyrian ethnology that was linked to the Assyrian Ch. of E. Recent writers have taken a more nuanced position, allowing both names, Assyrian and Chaldean, as ‘symbols of ethnic identity and pride’ appropriate to Christians with ancient roots in Mesopotamia, yet preferring Chaldean as reflecting ‘a more comprehensive and generic identity’ (S. Jammo).