Cults and secret societies
This imagery dominates Casaubon's personal life for a significant chunk of time. He loves to think about the mysterious Knights of Templar, and his political considerations tend to lean toward paranoia. He sometimes becomes convinced that secret societies are responsible for the flow of history. This imagery makes him acknowledge the disproportionate nature of power, and it also makes him consider the nature of coincidence. Perhaps there is a secret rhythm to daily life that someone is in control of.
Alchemy and metallurgy
Alchemical imagery is another dominant imagery, especially after the mystic journey to Brazil. When Casaubon returns, he learns that Belbo has made impressive progress in understanding the alchemical process of metallurgy and transmutation. This is a partner imagery to the esoteric cult imagery of the Knights of Templar, because there are hermetic texts whose contents are alchemical and esoteric (in fact most alchemical texts are esoteric), and by publishing their findings, they also turn their own experiences into gold through the magic of language.
Gnosticism and mysticism
Gnosticism is the religious departure from orthodoxy that shaped the early Middle Ages of European history. The Gnostics were the main mystic cults that disputed the Catholic church and its alleged authority. Sometimes the Gnostics celebrated texts that were not canonized by the church. In this novel, Belbo and Casaubon relate to Gnosticism deeply, in part because they explore mysticism through their studies, but also in part because they sympathize with the feelings of rejection and loneliness that come from being labeled as a heretic. They aren't religious heretics; they are political heretics, because they don't believe the myths that dominate Italian policy in their time.
Political correctness and orthodoxy
The imagery points to Italian politics, although that seems at some points completely separate. The connection between Belbo and Casaubon's mysticism with politics is illustrated when Casaubon says that his choice to study Philology is like a political statement. The statement is that they will be autonomous authorities on truth and human nature by studying language and literature. This frees them from the strict beliefs that shape Italian majority politics. In this way, the identify a hidden imagery—there is an unspoken code that they should abide by political correctness to an orthodox set of beliefs and opinions. Of course, they choose not to, but this comes at a cost.
