Freemasonry had developed in England in the seventeenth century, but after 1715 had split into Jacobite and Hanoverian lodges. The lodge in Rome was Jacobite (pro Stuart) and mainly Catholic, but admitted Protestants, while that in Florence was Protestant Hanoverian but also admitted Catholics and atheists who supported the Whig position. As Clement was from Florence, he did not view a prominent Protestant fraternity in his hometown favorably.
James Francis Edward Stuart was living as James III of England in Rome where he conducted a Jacobean court in exile. In 1737 he learned that Hanoverian Freemasons had recruited so many French Catholics that they had taken control of the Grande Loge de France from the Jacobites. He asked Clement XII to issue a papal bull condemning Hanoverian Freemasonry in the Catholic countries of Europe.
At the same time, Cardinal André-Hercule de Fleury was chief minister of Louis XV of France. Fleury was focused on maintaining peace with Britain. Jacobite sympathizers in France had formed a secret lodge of Freemasons; their attempts to influence Fleury to support the Stuart faction led instead to raids on their premises, and Fleury urged Pope Clement XII to issue a bull that forbade all Roman Catholics to become Freemasons under threat of excommunication.
Clement wished to accommodate the king while not antagonizing Britain nor opposing Fleury's foreign policy. The bull was drafted from a religious rather than the political viewpoint and did not distinguish between Jacobean and Hanoverian Freemasonry.
He noted that membership of Masonic Lodges, "spreading far and wide and daily growing in strength", was open to men of any religion or sect, who were sworn to secrecy. The logic at the heart of the bull is expressed as follows:
The bull goes on to note that the growing rumor had caused several governments which considered it a threat to their own security to cause such associations to be "prudently eliminated". An expressed danger was the private rules that bound members, "that they do not hold by either civil or canonical sanctions."
As a result, all Catholic participation in Masonry was prohibited, and bishops were to proceed against it "as well as inquisitors for heresy...calling upon the aid of the secular arm," as it was under suspicion of heresy, partly because of its already notorious secrecy.