Unam sanctam[a] is a papal bull that was issued by Pope Boniface VIII on 18 November 1302. It laid down dogmatic propositions on the unity of the Catholic Church, the necessity of belonging to it for eternal salvation, the position of the Pope as supreme head of the Church and the duty thence arising of submission to the Pope to belong to the Church and thus to attain salvation. The Pope further emphasised the higher position of the spiritual in comparison with the secular order. The historian Brian Tierney calls it “probably the most famous of all the documents on church and state that has [come] down to us from the Middle Ages”.[1] The original document is lost, but a version of the text can be found in the registers of Boniface VIII in the Vatican Archives.[2]