The Key of Truth is a text identified by Frederick Conybeare as a manual of either a Paulician or Tondrakian church in Armenia. He studied the text as manuscript dated 1782 held at the library of Ejmiacin in Armenia, and published it as an English translation in 1898.Encyclopedia of Religion and Ethics Part 18 - Page 695 James Hastings, John A. Selbie - 2003 "The possible exception is The Key of Truth, which was discovered by FC Conybeare, translated from the Armenian,... It is a manual of ' Thondrakian ' or Paulician teaching and practice, mutilated unfortunately by the removal of almost a ..."
Conybeare claimed that the text was a servicebook of the medieval Paulicians, and it contains a rite of adult baptism with waterContra Patarenos Page 33 Hugh Eteriano, Janet Hamilton, Sarah Hamilton - 2004 "146 In 1898 FC Conybeare found a copy of The Key of Truth in a manuscript written in 1782, in the Library of Ejmiacin. He claimed that this was a servicebook of the medieval Paulicians, and it contains a rite of adult baptism with water ." and conscious omission of Trinitarian terminology.
There is scholarly consensus that The Key of Truth was used by sectarians with beliefs derived from the Paulicians, but scholars after Conybeare consider that these beliefs may have evolved since the Middle Ages.
References
External links English Translation of The Key of Truth at Archive.org