What is unam sanctum?

"Unam Sanctam" is a papal bull issued by Pope Boniface VIII in 1302, asserting the supremacy of the spiritual authority of the pope over secular rulers. It famously declares that "there is one holy church," and emphasizes that submission to the pope is necessary for salvation. This document was part of the broader conflict between the papacy and secular authorities during the Middle Ages, particularly in relation to the power of kings. Its strong assertions of papal authority have made it one of the most notable statements in the history of the Catholic Church.