If one were to read Pope Gelasius I’s Epistula 12 to Emperor Anastasius in a vacuum, one might draw the conclusion that Gelasius was a powerful pope, able to speak with considerable authority. Indeed, the letter is one of the oldest and boldest papal criticisms of a Roman emperor. It famously differentiates between the earthly authority, administered by the emperor, and the priestly authority, administered by the bishop of Rome. It also famously subordinates the earthly authority to the priestly on the premise that even emperors need the sacraments (and therefore the clergy) for their salvation. 1 But the letter does far more than offer a theoretical conceptualisation of a church/state binary; it censures the emperor’s past actions, condemns his theological advisors for heresy and insists that the correct interpretation of any theological question can only emerge from the see of Rome because of its special association with St Peter, the prince of the apostles. 2 If this were the only surviving document from Gelasius’ tenure, or if we were to read this text through the prism of what the papacy would become, then yes, rightly might we read Ad Anastasium as though Gelasius were a powerful and assertive pontiff, boldly censuring imperial folly and righting heretical wrongs around the world.