DIPTYCH, (I) Two writing-tablets hinged or strung together, used in the Roman empire for letters and documents, especially (made of bronze) for the discharge of time-expired soldiers ; also (made of wood or ivory, sometimes of gold or silver, and contain ing the sender's name and portrait) for a token of a consul's, praetor's or aedile's entrance into office, which he issued to his friends and the public generally (Gr. (5ihrvyos, two folding) .
(2) In the early Christian Church the names of eminent mem bers and benefactors, living or dead, were recorded on diptychs and read aloud from the ambo or from the altar, thereby securing the prayers of the church ; especially, in each church, were the names of those who had been its bishops recorded. The reading of these names during the canon of the mass gave rise to the term canon ization.
The diptych formed the germ of the elaborate system of f estol ogies, martyrologies and calendars which developed in the church. It went by various names in the early church—mystical tablets, anniversary books, ecclesiastical matriculation registers or books of the living. According to the names inscribed a diptych might be a diptycha episcoporum, diptycha mortuorum or diptycha vivorum.
The richly ornamented outsides of consular diptychs sometimes found their way into church treasuries, where they were eventually used as covers for copies of the Gospels, or for liturgical prayers; and their tradition was continued in the use of the diptych or trip tych form for works of Christian devotional art.
(R. A. S. M.)