Famuli vestrae pietatis

Famuli vestrae pietatis, also known by the Latin mnemonic duo sunt ('there are two'), is a letter written in 494 by Pope Gelasius I to Byzantine Emperor Anastasius I Dicorus on the relationship between religious and secular officials.

Famuli vestrae pietatis is a letter written in 494 by Pope Gelasius I to Byzantine Emperor Anastasius I Dicorus which expressed the Gelasian doctrine.

[1] According to commentary in the Enchiridion symbolorum, the letter is "the most celebrated document of the ancient Church concerning the two powers on earth.

"[2] The Gelasian doctrine articulates a Christian theology about division of authority and power.

"[3] This letter established the dualistic principle that would underlie all Western European political thought for almost a millennium.