The term “oikoumene,” from the present passive participle of the Gk. verb oikeō, “inhabit,” and used from the time of Herodotus (d. between 430 and 420 b.c.), means “the inhabited earth.” In the 20th century the Swedish archbishop N. Söderblom (1866–1931) was the first to use the term to describe the work of reconciling and uniting the separated churches (Reconciliation). The term caught on and resulted in its present use in the ecumenical movement (Ecumenism, Ecumenical Movement).

In a basic study of the history and meaning of the term “ecumenical” (1953), W. A. Visser ’t Hooft (1900–…