Probably the preeminent theological dictionary published in the twentieth century is the German-language Die Religion in Geschichte und Gegenwart. From 1908-2007 it went through four editions: RGG1 (1908-1913), RGG2 (1927-1932), RGG3 (1957-1962), and now the newly completed 4th edition, Religion in Geschichte und Gegenwart (1998-2005).
This 4th edition is now being published in English translation by Brill as Religion Past and Present: Encyclopedia of Theology and Religion, ed. Hans Dieter Betz (2007-). At Hekman Library we've received the first five volumes (A-Haz) so far, with seven more to come. These four editions, taken together, contain a chronicle of changes in theological thought over the course of the past century.
RGG1 was initially conceived in 1900 as a cross-disciplinary work which would incorporate the research of the new "history of religions school" and other liberal theological movements, as well as speak to the current situation of the church (hence the "gegenwart" (present) in its title. This "present" orientation was to be a corrective to the more academically oriented Realenzyclopaedie fuer protestantische Theologie und Kirche (3rd ed., 1896-1913), which formed the basis for the New Schaff-Herzog Encyclopedia of Religious Knowledge (1908-1912) [full-text online].
RGG2 (1927-1932) was a completely new work, covering a cross-section of German theological thought and reflecting the rise of neo-orthodoxy. Selected articles from it have been translated and published in Jaroslav Pelikan, Twentieth-Century Theology in the Making (3 vols., 1969-71).
RGG3 (1957-1962) had a more international character, with some contributors from throughout the world, but retained its fundamentally German Protestant orientation and its many articles of interest to German readers. The "present" focus continued (with articles on the ecumenical movement, the New Deal), and the Fraktur script of the first two editions was replaced by roman type.
RGG4 is a fundamentally new work. One notes that its title is now Religion in Geschichte und Gegenwart, dropping the definite article "Die", perhaps indicating a desire to conceive "religion" more generically, with more emphasis on world religions. In my next post I'll look at RGG4 and its English translation more closely.
For a good review of the history of RGG in its various editions, see John Fitzgerald, et al., "Religion in Geschichte und Gegenwart: The Past and Present of a German Theological Dictionary," Religious Studies Review 27.4 (Oct 2001):319-329 [ DOI: 10.1111/j.1748-0922.2001.tb00374.x ]