Prisca theologia
Prisca theologia holds that one true theology that is the real basis for all religions was given to man in antiquity. The term is believed to have first been used by Marsilio Ficino in the fifteenth century. The concept of a common thread running through all religions is a theme common to Neoplatonism, Hermeticism, Rosicrucianism and the Chaldean Oracles. Many like Ficino who wanted to unite all religions under one banner relied on the concept of prisca theologia.
Prisca theologia should not be confused with the perennial philosophy, both of which agree that there is such a thing as “a true religion” that was given to man in ancient times. Prisca theologia holds that the philosophy has undergone declining change and dilution as time has gone by. The oldest principle was the purest. The perennial philosophy does not claim such a decline- it simply states that this “true religion” periodically shows itself in different times, places and ways.