Anathem is a speculative fiction novel by Neal Stephenson, published in 2008. Major themes include the many-worlds interpretation of quantum mechanics and the philosophical debate between Platonic realism and formalism.
Anathem is set on and around the planet Arbre. Thousands of years prior to the events in the novel, society was on the verge of collapse. Intellectuals entered concents, much like monastic communities but focused on intellectual endeavors rather than religious practice. Here, the avout— intellectuals living under vows and separated from Sæcular society, fraa (derived from Latin frater) for male avout and suur (derived from Latin soror) for female avout — retain extremely limited access to tools and are banned from possessing or operating most advanced technology (at a level beyond paper and pen) and are watched over by the Inquisition, which answers to the outside world (known as the Sæcular Power). The avout are forbidden to communicate with people outside the walls of the concent except during Apert, a 10-day observance held only once every year, decade, century, or millennium, depending on the frequency with which a given group of avout is allowed to interact with the Sæcular world. Concents are therefore slow to change - unlike the rest of Arbre, which goes through many cycles of booms and busts.
Interaction between the avout and the Sæcular world is not, however, limited to Apert. The secular power may "Evoke", or remove from the concent, members of the avout, when needed to address pressing scientific ("theorical") issues facing Sæculars. Such removal is one of many "Auts" (ritual acts) performed on certain occasions – much like rituals or sacraments of the Roman Catholic Church. The act of removing an avout from a concent at the request of the Sæcular Power is called "Voco" (a Latin word meaning "I call": most of the technical words used in Anathem are derivations or puns on Latin words, cf. Lucub – a late-night study session – from the Latin lucubratio), or "evocation", the avout called being "evoked".