Do not be fooled by the monastic trappings of the book-cover. This is high-concept, big ideas, mind-bombing science fiction. By the time you are through the 800 page story, you will have had a philosophical, mathematical and cosmological education. Much like his Baroque cycle, the novel builds on real research.
Annoyingly, the research is obfuscated by placing the action on the planet Arbre (french for “Tree”), where the philosophers and concepts all have their own names. Instead of Pythagoras, we read about Andrakhones; instead of Occam’s Razor we read of The Steelyard and so on.
The reason for this is presumably to avoid endless discussions about the precise meanings of the philosophical stance of Andrakhones/Pythagoras, and instead focus on the story. The faux greeks are in some way all straw-men, to pad out the back-story and buttress various philosophical or cosmological positions.
The footnotes and acknowledgements for Anathem get their own web page. These help you discover the primary sources and the earthly thinkers behind the straw-men.
The philosophy and cosmological questions in the book run the gamut from basic Platonism to Husserlian phenomenology. You will learn some of the ideas Thales and Pythagoras, Plato, Saint Augustine, Leibniz, Kant, Mach, Husserl, and Godel brought forth. The Syntactic vs Semantic divide (on Earth called the Analytic vs Continental philosophical divide) is one thread through the story. This is not your typical sci-fi story.
Stephenson has basically hidden a philosophical primer in the guise of an apocalyptic sci fi novel. My favorite parable/story is a discussion on the nature of consciousness. This becomes important later on, when we apply it to the many-worlds interpretation of cosmology. Anyway: The Bat-Fly-Worm story goes a bit like this: imagine a world with an ideal Bat (all hearing, ultrasound echoes, flying), an ideal Fly (all eyes, flying), and ideal Worm (all touch sense, crawling). These three creatures co-exist in a cave. How do they communicate? How does a deaf Fly describe something to the blind Worm, or vice versa?
The Fly-Bat-Worm is a metaphor for consciousness – our senses report a multitude of distinct, disparate sensory inputs that our consciousness sorts into a coherent whole. How do we build a perception of continuous time, when all we have are distinct observations? The argument in Anathem is a lot more enjoyable to read than the original Husserl.
The major question in the novel is Platonic in nature: the Platonic Ideal world (or Hylean Theoric World, in Arbre) is real in the many-worlds sense. Pi exists independently of observers, it exists independently of the universe. Pi is constant in the ideal world of plane geometry, no matter which of the many universes you calculate it in. Pi is something we discover, rather than invent. Similar to the allegory of the cave, there is a series of levels between the ideal world and the real world. Anathem proposes that these levels all exist as parallel universes, and that information flows between these universes in an acyclic directed graph. The idea of Pi flows from the Platonic Ideal world through the multi-verse into our own, occasionally bumping into a consciousness that is affected by it. Feel free to laugh and ridicule the concept now.
There is an acknowledged indirect intellectual debt to the Clock of the Long Now. The idea of the Long Now suffuses the society the book focuses on. The “mathic” world is monastic and focused on the long term, while the outside “sæcular” world is much like our own: short-term and distracted by blinkenlights and money. The “mathic” world sees the skyscrapers outside come and go as the “sæcular” civilization rises and collapses.
The idea that a monastic society can be so separate from its surrounding society for so long seems far-fetched, but the continued existence of the Amish would seem to show that it is possible. In any case, the idea of a community focused on long term thinking rather than on short-term satisfaction, of thinking beyond the next millennium rather than just the next quarter, is well worth pursuing. Anathem deserves respect for pushing the concept to its extreme, just to see what happens.
So Anathem is not exactly an easy read, but if you enjoyed the Baroque cycle or Cryptonomicon, or if you liked the bits of Snowcrash that discussed linguistics and Sumerian myth, then Anathem might be the book for you.