Opening Passage: The opening passage deserves to be quoted in full:
That was when I saw the Pendulum.
The sphere, hanging from a long wire set into the ceiling of the choir, swayed back and forth with isochronal majesty.
I knew--but anyone could have sensed it in the magic of that serene breathing--that the period was governed by the square root of the length of the wire and by π, that number which, however irrational to sublunar minds, through a higher rationality binds the circumference and diameter of all possible circles. The time it took the sphere to swing from end to end was determined by an arcane conspiracy between the most timeless of measures: the singularity of the point of suspension, the duality of the plane's dimensions, the triadic beginning of π, the secret quadratic nature of the root, and the unnumbered perfection of the circle itself.
I also knew that a magnetic device centered in the floor beneath issued its command to a cylinder hidden in the heart of the sphere, thus assuring continual motion. This device, far from interfering with the law of the Pendulum, in fact permitted its manifestation, for in a vacuum any object hanging from a weightless and unstretchable wire free of air resistance and friction will oscillate for eternity. (p. 3)
Summary: Foucault's Pendulum, in other words, is a true conspiracy theory, a real manifestation of that which all conspiracy theorists of any kind try to achieve. The suggestion of some ideal, perfect idea ("the singularity of the point of suspension") from which hidden secrets of the world (like the rotation of the world) can be discerned if one just finds the right swing of thought, putting together the underlying secrets of the world's process ("a higher rationality," "however irrational to sublunar minds") in a perfectly logical manner: this is what is promised. But in the real world, there is air resistance and friction, so the theory does not operate on its own, but must be built in such a way as to assure "continual motion", an ever-changing shifting of ideas. The human mind wants to know, and gnosis is one of our greatest temptations, to substitute 'being in the know' for genuine knowing. Hungering for knowledge of good and evil, we will eat the poison promising to provide it, for it seems good to look on, and to taste, and to make us see the world from a God's-eye point of view.
In the 1970s, the narrator, Casaubon (whose name evokes the character in Middlemarch who seeks the Key of All Mythologies), is doing a graduate thesis in history on the Knights Templar, when he happens to meet up with Belbo, an editor in a publishing house that often receives manuscripts from kooky conspiracy theorists talking about the Templars. He asks Casaubon to consult on one of these manuscripts, by a certain Colonel Ardenti, and he meets Diotallevi, another of the employees of the publishing house. Ardenti claims to have found a secret manuscript in code that lays out a plan by the Templars after their suppression to discover a great treasure. The book deal is never completed, however, because Colonel Ardenti disappears suddenly, apparently killed, except that the corpse seen by the (unreliable) witness has also disappeared. Nothing seems to come of it, and Casaubon continues his separate way. He spends some time in Brazil, then returns to Milan and starts a freelance research firm; while there, he meets a woman, Lia, in the library, and they fall in love and eventually have a child.
By happenstance he meets up with Belbo again, and is hired by the publishing house. It's actually a sort of scam -- there is a respectable publishing house front, Garamond, but but it is linked secretly with another publishing brand, Manutius (or Manuzio in the original Italian), that is a vanity press. People come in through Garamond, and if they are among the crazy kooky conspiracy theorists, they get nudged over to Manutius where, if they want to get published -- and they are usually desperate for the respectability of being published -- they pay to have their work published. Manutius then goes through a bit of song and dance of distributing and advertising their authors, but it is all to the very profitable end of squeezing more money out of the authors, because Manutius makes its profits from authors, not readers.
Faced with endless manuscripts from kooky conspiracy theorists, Casaubon, Belbo, and Diotallevi start a game of making a better conspiracy theory than any of them, starting with Ardenti's manuscript, taking anything useful from the manuscripts received, and adding to this from their own knowledge, since they are better educated than most of the authors. They call it the Plan. But as the Plan gets more intricate and coherent, it gets out of control. They become habituated to thinking in conspiracy-theory terms, and when members of the occult community discover hints of the Plan, they become intent on capturing it at any cost. But after this point it becomes increasingly difficult to tell what is real and what is imagined, because Casaubon himself is losing his ability to tell the difference. The glibness with truth that was at the heart of the intellectual game they were playing has begun to spread like cancer.
What generally saves us from the temptation of gnosis is the hylic mud of mundane life, and for most of the book Casaubon is kept grounded by his relationship with Lia and their child. But there is only so far you can train your mind to spin out connections before it begins to do it whether you want it to do so or not.
One of the things Eco does throughout is draw parallels between conspiracy-theory thinking and other things in life that we take as perfectly normal. There is not a vast difference between what conspiracy theorists do and the sort of nonsense people in which people involve themselves in politics; it is precisely the similarities that trap Belbo. Nor are conspiracy theories so very different from how we approach economic matters, and it is not an accident that the publishing house at which the three main characters work is itself a conspiracy. Politics and economics are precisely points in our lives at which we tend to blur, sometimes deliberately, the line between true and imaginary, and are also points at which we tend to run to overarching, all-explaining, yet ever-changing theories based on simple ideas. The Pendulum swings through all the variations, but it always suggests higher knowledge, the ability to be one of those 'in the know', if you only capture the right key to everything.
Favorite Passage: I actually had two this time around and couldn't decide between them, so I'll put them both up.
Perhaps because I was in daily contact with Lia, and with the baby, I was, of the three, the least affected by the game. I was convinced I was its master; I felt as if I were again playing the agogô during the rite in Brazil: you stay on the side of those who control the emotions and not with those who are controlled by them. About Diotallevi, I didn't know then; I know now. He was training himself viscerally to think like a Diabolical. As for Belbo, he was identifying at a more conscious level. I was becoming addicted, Diotallevi was becoming corrupted, Belbo was becoming converted. But all of us were slowly losing that intellectual light that allows you always to tell the similar from the identical, the metaphorical from the real. (pp. 386-387)
Hadn't Agliè spoken of the yearning of mystery that stirred the age of the Antonines? Yet someone had just arrived and declared himself the Son of God, the Son of God made flesh, to redeem the sins of the world. Was that a run-of-the-mill mystery? And he promised salvation to all: you only had to love your neighbor. Was that a trivial secret? And he bequeathed the idea that whoever uttered the right words at the right time could turn a chunk of bread and a half-glass of wine into the body and blood of the Son of God, and be nourished by it. Was that a paltry riddle? And then he led the Church fathers to ponder and proclaim that God was One and Triune and that the Spirit proceed from the Father and the Son, but that the Son did not proceed from the Father and the Spirit. Was that some easy formula for hylics? And yet they, who now had salvation within their grasp -- do-it-yourself salvation -- turned deaf ears. Is that all there is to it? How trite. And they kept on scouring the Mediterranean in their boats, looking for a lost knowledge of which those thirty-denarii dogmas were but the superficial veil, the parable for the poor in spirit, the allusive hieroglyph, the wink of the eye at the pneumatics. The mystery of the Trinity? Too simple: there had to be more to it. (p. 514)
Recommendation: It takes a particular mood, but Highly Recommended.
Quotations from Umberto Eco, Foucault's Pendulum, William Weaver, tr. (Ballantine: 1989).