Review: Permutation City (Greg Egan)

Book: Permutation City, by Greg Egan (1979).
2.2k words (≈ 8 minutes)

One way to classify science fiction works is by the scope of the speculative concepts in the work.

For example, the first tier could contain works in which the only speculative elements are things with non-Earth-shattering consequences. Maybe dinosaur DNA could somehow remain intact for over sixty million years. Maybe an evil organization is plotting to create a pandemic.

Then there would be works in which the speculative element is something paradigm-shifting. What if humans made contact with aliens? What would an artificial intelligence do? What if genetic engineering were cheap and widespread?

The level after that would be works that ask similar questions, but go deeper into their consequences, especially by exploring what they say about human nature. How do you tell whether reality is simulated? Can humans even understand sufficiently advanced aliens? What does the possibility of artificial intelligence say about consciousness?

And the last tier is works in which the whole point is speculating about the ultimate nature of the universe itself. Isaac Asimov’s short story "The Last Question" is a classic example. Greg Egan’s 1994 novel Permutation City is another.

(It is hard to limit spoilers in this review, since the plot of the book is very tightly wound to the questions it explores. You have been warned.)

Copies everywhere

The first paragraphs are as pedestrian as it gets: our protagonist, Paul Durham, wakes up in a room and looks around.

Oh, and Durham is inside a computer (literally, though not too literally). He is a “copy”; the “original” had a brain scan made of himself, and started running that in a computer. The simulated reality isn’t an exact copy: only brains are simulated in any detail, while the rest of the environment is an approximation, though a photorealistic one, to save on running costs. Even on economy mode, though, copies in the 2050 world of Permutation City run at best at less than one tenth the speed of the real world.

In the novel’s world, many rich clients have their brains scanned before their biological death, and the copies started after they die. However, they cannot retreat into their virtual worlds, since copies can be affected by real-world events, particularly because legally, they are software, not people.

The wealthiest copies run on private computers managed and paid for by a trust fund. Less wealthy ones run much slower, and their running speed depends on the price of computing power changes, which is traded on a global market (note that the book was published in the 1990s; cloud-based computing power as a service was probably not a very common idea).

What this means for the world of Permutation City is that in addition to private copies running relatively fast, there are also virtual slums of slow-running copies that can afford computing power only when it’s cheapest, and cannot generate new income because their slow running speed (tens or hundreds of times less than the real-world) makes them useless for most jobs. A subculture of poorer copies, calling themselves the "Solipsist Nation", tries to reject external reality completely.

Egan’s bleak vision of copy inequality is not one I have encountered before, and one that seems a bit too credible for comfort.

All the standard brain emulation -related questions are also given some space. To what extent is a copy, based on a brain scan done some time before a person’s death, really a continuation of the life of that person? What about the legal and moral status of a copy of a copy? In general, Egan keeps the sledgehammer on the wall when exploring moral questions, leaving readers to draw their own conclusions and instead focusing on characters’ reactions and attitudes to these questions.

Assemble from the dust?

Egan does, however, present a sustained speculative argument about the nature of copies and therefore consciousness. He presents a thought experiment, which, within the novel, is a literal experiment on thought.

Durham’s copy is conscious. That much can be granted; if consciousness is a byproduct of brain activity, there is no reason for it to not be present in a simulation of the brain.

(Egan is fairly conservative with the technical specifications of the copies; it is mentioned that the brain simulation is not accurate down to the quantum level, and that time for a copy proceeds in discrete time intervals of one millisecond of subjective time. Some might argue that continuous time and/or quantum-level simulation might be necessary for consciousness, but this is a topic that Egan wisely avoids.)

Next, the speed of copy-Durham’s subjective time can be slowed down and sped up by will, simply by changing the rate at which the simulation computes itself. This can be taken even further - if Durham’s copy were simulated only in bursts once every day, or at random intervals, or one frame today and the next frame in a thousand years, copy-Durham would feel no difference.

We can easily stretch the relative times of copies and the real world, but can we break any connection whatsoever between the two experiences of time? Permutation City assumes yes: the frames of the copy’s simulation can be sliced up and rearranged, and the thread of subjective experience will still continue from the perspective of the copy as if nothing were happening even when the simulation is hopping back and forth from one time to another when viewed from the external world.

This is the critical step, and, I think, the weak link. To be able to slice up the copy’s time, the simulation must be able to set itself to, say, the frame at time t=2, and then later to the frame at t=1.

But how can the simulation know the contents of the frame at t=2? It must first compute all preceding frames. After it has done so, of course, there is no obstacle to the simulation loading one frame into memory as the current state, then another and another, all out of order. But is this arbitrary procedure of loading frames into the simulation’s memory what causes the experience of consciousness for the person being simulated? Or would the initial computation of the states be the key?

At one point copy-Durham wonders what his subjective experience of consciousness really is: the current time slice loaded in the simulation, the computation of those time slices, or something else? The novel’s answer seems to the first option.

This raises some very interesting questions. If we reject this premise, the other alternative seems to be that it is the process of computation of frames that causes them to “occur” in the simulation, at least from the perspective of conscious beings in the simulation. This is an interesting topic, and raises many questions. Might the real world, then, be thought of as a computational procedure, in the sense that it is the “computation” of the next moment that makes it happen?

If that sounds like too much to accept, consider what it would mean for the view in the book to be correct: consciousness can thread its way through the disconnected slices of the simulation and therefore the subjective time within the simulation is entirely independent of real-world time. Egan then adds a dose of solipsism: the thread of consciousness of the simulation is real, for the experiencer, despite the fact that it has nothing to do with the “real” time of the outside universe. It has, in other words, somehow “assembled itself from dust”, as Egan likes to repeat, including the italics.

If copy-Durham can assemble itself from the dust despite the time slices of his simulation being scrambled, then why couldn’t other things assemble themselves from the dust?

Extrapolate this further. Imagine a universe of nothing more than an arbitrarily large space of random fluctuations; some of them would, by chance, form sequential, coherent timelines containing conscious entities, which would then be experienced by those entities. Our reality, in the solipsist universe of Permutation City, would just be one of these sequences.

And that’s only the first fourth of the book.

Immortality = cellular automata + solipsist cosmology

What applications could the idea of assembling from the dust ever have? Eternal life and near-omnipotence, apparently.

The other main character, Maria Deluca, is a software engineer who spends a lot of the time she should be working on playing around with the “Autoverse”, a massively complex cellular automata with its own system of chemistry that mirrors real-world chemistry, except without quantum effects (I get the feeling Egan is not fond of quantum physics). Egan spends a lot of pages on the Autoverse, but it is worth it; I found myself wishing for a real one.

After Maria gains some success with getting Autoverse bacteria to mutate, Durham enlists her to design a program to produce an entire planet, complete with primitive bacteria, in the Autoverse. There is not nearly enough computing power, even in Egan’s world of 2050, to run an entire Autoverse planet, but that’s not the point.

Durham’s idea is to simulate the first few minutes of a self-replicating cellular automata computer on a computer, and then stop. The continuation of the self-replicating computer represents a coherent timeline and by the logic of the novel’s solipsist universe, it will simply assemble itself from the dust and continue to exist from the perspective of the wealthy clients who paid to have their copies put on the thing. Thus Durham, and his clientele of billionaires, escape our reality into an alternative universe consisting of an ever-expanding computer that simulates their copies in addition to the Autoverse planet.


If this weren’t speculative enough, Egan turns the solipsism up to eleven in the second part of the book.

Without revealing too much, the basic idea is that the Autoverse planet has developed intelligent life, which has its own theories for the origin of their universe that do not include being a simulation inside a simulation that was launched by a simulation made by a crackpot theorist and a dozen billionaires hoping for eternal life.

Reality in the universe (or should I say, space of random states) of Permutation City is a subjective thing, and so the logically coherent theories of the simulated lifeforms eventually become more real than the version of reality Durham and the other copies believe in, with destabilizing effects on their apparently-not-quite-eternal universe.

Brain emulation is already a topic with plenty of philosophical questions to explore. Egan, though, is not content with remaining in that territory, and instead takes the reader on a philosophical roller coaster through the consequences of ever wilder and wilder solipsism.

I was told you have to mention literary features when discussing literature …

… but Permutation City was written more for its concepts than its literary merit.

Egan does portray a reasonably diverse cast of characters. We have an eccentric and determined theorist, a software engineer with a terminally ill mother and time-consuming hobbies she cannot bring herself to quit, a remorseful billionaire struggling with past crimes, and a survival-oriented virtual slum -dweller. Many of them struggle in a genuine way with questions of identity and morality in the copy-filled world of Permutation City, and some scenes were touching, but none of the characters were particularly memorable.

Many of Egan’s chapters (not all are named) have names that are anagrams of "Permutation City", an allusion to the slicing of copy-Durham’s simulation. “Remit not paucity” is the most common chapter name. As far as I can tell, it seems to be a warning against trying to eliminate all scarcity from life, as Durham’s flawed universe does. There is also a disconcerting heavily anagrammatic poem at the front of the book, indirectly attributed to the main character Paul Durham. If it has meaning besides building atmosphere, I can’t figure it out.

Meaningful answers?

Permutation City is far from the only work of science fiction to explore esoteric philosophical themes. Peter Watts’ Blindsight (main point: how useful is consciousness; what if a space-faring civilization did not have it?) and Neal Stephenson’s Anathem (main point: uhhh …) also deal with the philosophical questions surrounding consciousness.

However, Permutation City is exceptional in the extent and scope of its speculation. It is also structured well in this regard; Egan gradually ramps up the level of speculation throughout the work, allowing the reader to update their knowledge of how the novel’s world works after the introduction of each speculative leap, and helping to maintain immersion by showing the internal consistency. It also, probably not coincidentally, lays bare Egan’s chain of reasoning, exposing it to readers for easy analysis. The book definitely succeeds in provoking questions.

As to whether the book’s big ideas are anywhere close to being correct, I think Isaac Asimov’s fictional computer in The Last Question put it best:

1 comment:

  1. I don’t know Egan but I think he both understands and likes quantum theory. Perhaps in this case he wants to avoid some obvious issues (no quantum cloning, quantum simulation on classical computers maybe exponentially slow, etc).