36. This manner of acting of St. Boniface, in which his respectful homage towards the Roman Pontiffs is seen most clearly, has always been faithfully followed, as you know well, Venerable Brothers, by all those who have kept in mind that the Prince of the Apostles was placed by our Divine Redeemer as the firm rock upon which is built the universal Church, which will last until the end of time, and that to him also were given the keys of the kingdom of heaven and the universal power of binding and loosing.⁴⁰ Those who reject rock and try to build without it certainly lay the foundations of a tottering edifice upon shifting sands; their efforts, works and undertakings, as all human things, cannot be solid, cannot be firm and stable, but - as both ancient and modern history show - must almost necessarily undergo change as time goes on, due to contradictory human opinions and the vicissitudes of human events.