- A belief in four gods.
- (Christianity) The belief that there are four elements in the Christian Godhead—the three hypostases (Father, Son, Holy Spirit) of the Trinity and a divine essence out of which each of these originates.
2002, Hauben, Hans, “On the Invocation of the 'Holy and Consubstantial Trinity' in Byzantine Oath and Dating Formulas”, Zeitschrift für Papyrologie und Epigraphik, volume 139, Bonn: Dr. Rudolf Habelt GmbH, ISSN 00845388, JSTOR 20191434, page 160:
- […] "consubstantial Trinity" could have been a reaction against the supposed heresy of […] Damian […] who was accused of "tetratheism" (or "tetradism", distinguishing four different entities in the Godhead), a response to, but as it seems a variant of, the very influential "tritheism" of John Philoponus (distinguishing three Deities in the Trinity) […]
- For more examples of usage of this term, see Citations:tetratheism.
- “tetratheism”, in The Century Dictionary, New York: The Century Co., 1911
- Tetratheism in Chambers's Twentieth Century Dictionary, London, W. & R. Chambers, 1907. p. 1003.
- Tetratheism in Canney, Maurice A. An Encyclopaedia of Religions, London, G. Routledge, 1921. p. 351. OCLC 652285640.
- Hook, Julius N. The Grand Panjandrum and 2,699 Other Rare, Useful, and Delightful Words and Expressions. Revised and expanded. New York: Collier Books, 1991. p. 132. ISBN 9780020332886.