Permutation City

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Permutation City
Cover of first edition (hardcover)
Author Greg Egan
Country Australia
Language English
Genre Hard science fiction, Postcyberpunk
Publisher Millennium Orion Publishing Group
Publication date
Media type Print (Hardcover and paperback)
Pages 310 pp
ISBN ISBN 1-85798-174-X
OCLC 30834713
Website Official website

Permutation City is a 1994 science fiction novel by Greg Egan that explores many concepts, including quantum ontology, via various philosophical aspects of artificial life and simulated reality. Sections of the story were adapted from Egan's 1992 short story "Dust" which dealt with many of the same philosophical themes.[1] Permutation City won the John W. Campbell Award for the best science-fiction novel of the year in 1995 and was nominated for the Philip K. Dick Award that same year. The novel was also cited in a 2003 Scientific American article on multiverses by Max Tegmark.[2][3]

Themes and setting[edit]

Permutation City asks whether there is a difference between a computer simulation of a person and a "real" person. It focuses on a model of consciousness and reality, the Dust Theory, similar to the Ultimate Ensemble Mathematical Universe hypothesis proposed by Max Tegmark. It uses the assumption that human consciousness is Turing computable: that consciousness can be produced by a computer program. The book deals with consequences of human consciousness being amenable to mathematical manipulation, as well as some consequences of simulated realities. In this way, Egan attempts to deconstruct notions of self, memory, and mortality, and of physical reality.

The Autoverse is an artificial life simulator based on a cellular automaton complex enough to represent the substratum of an artificial chemistry. It is deterministic, internally consistent and vaguely resembles real chemistry. Tiny environments, simulated in the Autoverse and filled with populations of a simple, designed lifeform, Autobacterium lamberti, are maintained by a community of enthusiasts obsessed with getting A. lamberti to evolve, something the Autoverse chemistry seems to make extremely difficult.

Related explorations go on in virtual realities (VR) which make extensive use of patchwork heuristics to crudely simulate immersive and convincing physical environments, albeit at a maximum speed of seventeen times slower than "real" time, limited by the optical crystal computing technology used at the time of the story. Larger VR environments, covering a greater internal volume in greater detail, are cost-prohibitive even though VR worlds are computed selectively for inhabitants, reducing redundancy and extraneous objects and places to the minimum details required to provide a convincing experience to those inhabitants; for example, a mirror not being looked at would be reduced to a reflection value, with details being "filled in" as necessary if its owner were to turn their model-of-a-head towards it.

Within the story, "Copies", digital renderings of human brains with complete subjective consciousness, the technical descendants of ever more comprehensive medical simulations, live within VR environments after a process of "scanning". Copies are the only objects within VR environments that are simulated in full detail, everything else being produced with varying levels of generalisation, lossy compression, and hashing at all times.

Copies form the conceptual spine of the story, and much of the plot deals directly with the "lived" experience of Copies, most of whom are copies of wealthy billionaires suffering terminal illnesses or fatal accidents, who spend their existences in VR worlds of their creating, usually maintained by trust funds which independently own and operate large computing resources for their sakes, separated physically and economically from most of the rest of the world's computing power, which is privatized as a fungible commodity. Although the wealthiest copies face no financial difficulties, they can still be threatened because copies lack political and legal rights (they are considered software), especially where the global economy is in recession. Hence they cannot afford to retreat into solipsism and ignore what is happening in the real world.

At the opposite end from the wealthy Copies are those who can only afford to live in the virtual equivalent of "Slums", being bounced around the globe to the cheapest physical computing available at any given time in order to save money, while running at much slower speeds compared to the wealthy Copies. Their slowdown rate depends on how much computer power their meager assets can afford, as computer power is traded on a global exchange and goes to the highest bidder at any point in time. When they cannot afford to be "run" at all, they can be frozen as a "snapshot" until computer power is relatively affordable again. A Copy whose financial assets can only generate sufficient interest to run at a very slow rate is stuck in a rut because he/she/it becomes unemployable and is unable to generate new income, which may lead to a downward spiral.

By creating this scenario, Egan postulates a world where economic inequality can persist even in one's (virtual) afterlife.

The concept of solipsism is also examined prominently, with many less-wealthy Copies attending social functions called Slow Clubs, where socialising Copies agree to synchronise with the slowest person present. Many of these less-wealthy Copies become completely deracinated from their former lives and from world events, or else become Witnesses, who spend their time observing (at considerable time lapse) world events unfold, at the cost of any meaningful relationships with their fellow Copies. A subculture of lower/middle-class Copies, calling themselves Solipsist Nation after a philosophical work by their nominal founder, choose to completely repudiate the "real" world and any Copies still attached to it, reprogramming their models-of-brains and their VR environments in order to design themselves into their own personal vision of paradise, of whatever size and detail, disregarding slowdown in the process.

Egan's later novels Diaspora and Schild's Ladder deal with related issues from other perspectives.


The plot of Permutation City follows the lives of several people in a near future reality where the Earth is ravaged by the effects of climate change, the economy and culture are largely globalised, and civilisation has accumulated vast amounts of cloud computing power and memory which is distributed internationally and is traded in a public market called the QIPS Exchange (Quadrillion Instructions Per Second, see MIPS).

Most importantly, this great computing capacity is used to construct physiological models of patients for medical purposes, enabling the creation of Copies, whole brain emulations of "scanned" humans which are detailed enough to allow for subjective conscious experience on the part of the emulation. Scanning has become safe enough and common enough to allow for a few wealthy or dedicated humans to afford to create backups of themselves.

A minority of Copies exist, though they are largely perceived as being a collection of the thanatophobic eccentric rich. Copies do not yet possess human rights under the laws of any nation or international body, although some of the wealthiest Copies, those still involved with their own estates or businesses, finance a powerful lobby and public relations effort to advance the Copy rights cause.

The plotline travels back and forth between the years of 2045 and 2050, and deals with events surrounding the life of a Sydney man named Paul Durham, who is obsessed, yet frustrated, with experimenting on Copies of himself (because he believes Copies of himself should be more willing to undergo experimentation). In the latter time frame, Durham is suspected to be a con artist of some type, who travels around the world visiting rich Copies and offering them prime real estate in some sort of advanced supercomputer which, according to his pitch, will never be shut down and will be powerful enough to support any number of Copies in VR environments of their own designing at no slowdown whatsoever, no matter how preposterously opulent those environments might be.

He pitches this concept to the Copies, predicated upon the prediction that the Copy rights movement might run into resistance due to devastating climate change. As the world undergoes increasingly extreme and erratic weather, a variety of international bodies, especially the Association of Southeast Asian Nations, which has been particularly hard-hit by tropical storms, have proposed projects to use their vast computing resources to attempt to intervene, utilising chaotic effects to their advantage, in global weather patterns with such precision as to minimise weather-related destruction while also minimising the scale of the efforts necessary to do so. Durham predicts this will clash with the spread of Copy rights, as both Copies and weather simulations will demand increasing QIPS Exchange shares in the future. All that each Copy must do is to make the laughably small investment of two million ecus in order to bring Durham's fantasy computer into existence.

As part of his plot, Durham hires Maria Deluca, an Autoverse enthusiast. She has recently become famous within the small community of Autoverse hobbyists for developing a variety of A. lamberti which evolved the capacity to metabolise an Autoverse toxin. Durham contacts her and offers to pay her thirty thousand dollars to design an Autoverse program which, given a large enough computer, could potentially evolve into a planet bearing Maria's own strain of evolvable Autoverse life. She desperately wants the money to have her dying mother scanned into a Copy. Since no such computer to fully evolve Autoverse life exists, Durham has to try to convince Maria that he is a wealthy Autoverse enthusiast interested in her evolvability results and looking for a proof of concept for a much larger system. He also clandestinely commissions a famous virtual reality architect, Malcolm Carter, to build a full scale, high resolution VR city, Permutation City, the largest VR environment ever conceived, complete with reactive crowds and a staggering variety of full scale, high resolution scenic views.

As computer fraud investigators begin to close in on Durham's scheme, Maria is pressured by police into covertly gathering evidence in order to incriminate Durham, while continuing to work for him. She learns more about Durham himself, including his time spent in psychiatric care and his callous experimentation on his own Copies, as well as his assiduously reticent Copy backers.

Meanwhile, two Slum-dwelling Solipsist Nation Copies, Peer and Kate, explore their post-human existences as well as their strained but loving relationship, until Kate's long-time friend Malcolm Carter offers to secretly hack them both, along with any moderately-sized software packages they wish, into Permutation City's machine code, guaranteeing them a place in the city were it ever to run, but permanently debarring them from manipulating the city's implementation for fear of being deleted as extraneous cruft by automated optimisers.

At the end of Part One, Durham reveals the full extent of his plan to Maria: after taking his earlier self-experiments to their logical conclusion, he became convinced of something he came to call the Dust Theory, which holds that there is no difference, even in principle, between physics and mathematics, and that all mathematically possible structures exist, among them our physics and therefore our spacetime. These structures are being computed, in the manner of a program on a universal Turing machine, using something Durham refers to as "dust" which is a generic, vague term describing anything which can be interpreted to represent information; and therefore, that the only thing that matters is that a mathematical structure be self-consistent and, as such, computable. As long as a mathematical structure is possibly computable, then it is being computed on some dust, though it does not matter what dust actually is, only that there be a possible interpretation where such a computation is taking place somehow. The dust theory implies, as such, that all possible universes exist and are equally real, emerging spontaneously from their own mathematical self-consistency.

Due to the computability of consciousness and the function of consciousness as a matrix for interpretation, Copies hold the unique position of being the only conscious beings which themselves are not being computed by self-consistent mathematical rules (existing, of course, in virtual realities held together by heuristics merely for the sake of their experience). As such, in principle it should be the case that when a Copy is terminated and deleted, its own conscious experience will continue due to the fact that there is no precedent within the Copy's interpretive matrix by which the Copy should suddenly cease. Indeed, Durham himself claims to have been through such a process several times, each time finding himself back in "the real world" after deletion, with there existing some plausible explanation as to why he believed himself to have been a Copy who was deleted, though with each successive experience of Copying himself and being deleted, he gradually became increasingly confident that the experiences were actually the result of his consciousness finding a logical interpretation in which it had not actually ceased, rather than each successive experience being ultimately true and real.

Because of this, Durham is staging a massive, momentary buyout of the world's processing power to simulate a minute or two of a "Garden of Eden" configuration of an infinitely-expanding, massively complex cellular automaton universe (similar to what is known as a "Spacefiller" configuration in Conway's Game of Life) based on a fictional, Turing-complete cellular automaton known as TVC ("Turing/Von Neumann/Chiang", named after its conceiver and designer), in which each iteration of the expansion serves to "manufacture" an extra layer of blocks of a computing configuration. Ultimately, if a Copy were to be run in such a self-consistent universe, and were to observe, via a series of pre-defined experiments, the cellular nature of its own processing implementation, then there would be precedent for that self-consistent "TVC universe" to persist in its own terms even after its termination and deletion in the universe it was designed and launched in. His and his investors' Copies would therefore persist indefinitely in the simulation, and since the "space" of the TVC universe would be made of self-reproducing cellular automaton computer processors, the simulation would not possess a finite number of states and the passengers would not, in principle, run out of interesting things to get up to.

Implanting himself and his investors in this TVC universe, Durham believed he could prove or falsify his hypothesis that his experience of repeated termination and continuation was the result of his own interpreting himself into universes in which he might plausibly have believed he had had such an experience, as opposed to merely having inhabited such a universe all along. If he were to implant his Copy into the TVC universe, have the copy run a number of experiments to anchor itself in that universe, and then terminate it, only to find himself still in the TVC universe (indeed, the purpose of growing the TVC universe from a Garden of Eden configuration was to prove to his Copy that such a TVC universe as it found itself to inhabit must have been launched from a non-TVC universe, as opposed to merely having always existed and evolved towards this the current state in which he did not know whether it had) rather than back in "the real world" again, then he would be vindicated; if not, then his hypothesis would be falsified and he might consider himself crazy (his last several experiences of termination and subsequent continuation involved him finding himself in the position of having been recently cured of psychosis). The Autoverse planetary seed program designed by Maria was to be included in the TVC universe package for his investors to explore once life had evolved there after it had been run on a significantly large segment of the TVC universe.

Though Maria believes Durham to be obviously rationalising his experiences while psychotic, she agrees to Durham's request to have herself scanned and inserted into the TVC launch as an on-hand Autoverse expert. The six-hundred thousand dollar fee will allow her mother to be scanned, and she is certain that her copy will never wake because she demands to be present at the launch to verify that her copy is not run during the launch period, and is subsequently deleted.

After a successful launch, simulation, termination, and deletion of the TVC universe, Durham and Maria have uncomfortable sex in awkward celebration, and later that night, while Maria is asleep, Durham disembowels himself with a kitchen knife in his bathtub, believing his role as the springboard for his deleted TVC Copy to discover its true identity to be fulfilled.

Part two[edit]

Maria wakes in Permutation City seven thousand years of subjective time after the launch, furious at Durham for being awoken and refusing to believe that the launch was successful. Durham eventually persuades her, however, by showing her the complexity of the Autoverse planet she had designed, Planet Lambert, which had then been running on a suitably large chunk of the TVC universe for several billion subjective years. Intelligent life in the form of complex swarms of insect-like eusocial beings had evolved on Lambert from Maria's original Autobacterium hydrophilus, and the citizens of Permutation City were on the verge of making contact with the creatures. However, a democratic vote among the population of Permutation City restricted the Autoverse scholars from making contact until the creatures had independently hypothesized the existence of a creator. Meanwhile, Permutation City had flourished in the TVC universe, and the original inhabitants of a few hundred had exploded to a population of tens of thousands, with the descendants of the various founders sharing their founders' ever growing chunks of the TVC universe, with Permutation City acting as the central locus for interaction between populations located in different contiguous blocks of the universe.

Durham, however, confides in Maria that he does not believe the insectoid creatures will ever seriously consider the concept of a creator and intends to use Maria's slice of the universe's processing power (as a founder of the world she was given de facto control of a continuously-growing zone of the processor network as well) to make forbidden first contact with the life of Planet Lambert. He believes this is necessary because he has seemingly lost the ability to pause the Autoverse simulation or slow it down past a constant multiple of the size of the processor network it occupies. Durham is worried that the rules of their simulated universe are breaking down.

What they discover together is that the growing and intellectually voracious population of Planet Lambert has exceeded the combined intelligence of the inhabitants of the remainder of the TVC universe, and that Lambert in its Autoverse has ceased to be defined as the TVC universe's simulation. Rather, the Lambertians have been considering a new set of hypotheses, interpretations of the evidence present to them, which do not require their universe to have been created in Maria's original Garden of Eden configuration. As such, the TVC universe's processor networks, which had previously done the work of simulating the Autoverse for the inhabitants of Permutation City, were now progressively being redefined in ways which prevented them from interfering with the existence of the Autoverse in ways unprecedented under these newly self-consistent interpretations of its terms of existence – the TVC universe was being overwritten into a system existing solely as a byproduct of the self-perpetuation of the Autoverse, and its inhabitants on Planet Lambert had interpreted it to be so. Durham, Maria, and some other companions quickly launch an emergency expedition into the Autoverse to attempt to convince the Lambertians of the validity of the creator hypothesis and its methodological perferentiality over their own newly formulated theory.

Unfortunately, the Lambertians reject their presentation of the creator theory of the Autoverse on the grounds that a system such as the TVC universe, capable of simulating their own universe, would have to be infinitely sized or infinitely expanding, which they consider to be unparsimonious. Shortly after failing to convince Planet Lambert of the creator theory, the Lambertians inform them of the discovery a set of field equations with a stable solution for each of their universe's elements; furthermore, initial studies on the equations show that they predict the spontaneous instantiation of matter at high temperatures, enabling their world to come into existence without requiring the Garden of Eden Maria had initially designed.

To the alarm of its citizens, Permutation City and eventually the entire TVC processor-network begins to collapse into nothingness, interpreted out of existence by the Lambertians whose reality no longer requires a maker, there being a 'better' solution that has superseded its possibility. As Permutation City becomes corrupted and the TVC universe begins to suffer spontaneous systemic failures, Durham and Maria inform the inhabitants of the various founders' computing blocks of the situation while preparing a new TVC Garden of Eden based on the original to launch in their universe's final moments, though Durham initially declines to board it himself, saying he has become exhausted with the number of times he was awoken in new realities and would be unable to cope with experiencing it again. Ultimately, however, Maria convinces him to change his mind (literally reconfiguring it to desire escape) and together they leave, pledging to discover the underlying rules that governed the Autoverse's takeover of Permutation City.

See also[edit]


  1. ^ Aurealis Interview (2009) by Russell Blackford
  2. ^ Max Tegmark, Parallel Universes, Scientific American, May 2003
  3. ^ Max Tegmark, Parallel Universes

External links[edit]