The standard criteria for using apocalypses as
historical sources were established by the late
Byzantinist, Paul J. Alexander. Examining the
process of literary embellishment and adjustment of
a few Syriac and Greek apocalypses, he arrived at
the conclusion that historical apocalypses are in
fact “prophecies ex-eventu”, i.e.
having actually already materialised around the time
of their circulation. The amount of such material,
he argued, may serve as a kind of barometer for
measuring the eschatological pressure at a given
time in history since apocalypses are written to
provide comfort in times of tribulation,
particularly during grave military crises.