The last review I wrote of a Greg Egan book began with a consideration of what science fiction is and how to classify it. This time I’m tempted to do the same. Once again, a Greg Egan novel strikes very close to the heart of (one view of) what science fiction is about.

Science fiction is typically associated with some combination of space, dinosaurs, and time-travel. However, I’d argue that what makes for great science fiction is not time-traveling space dinosaurs, but ideas.

In addition to the typical literary elements of a novel, great science fiction explores scientific/technological/philosophical/sociological ideas in a way no other medium can match. This frequently has side-effects. Fewer pages are left for character development. The turning points of the plot often revolve around insights rather than drama and violence.

Diaspora takes this quality and turns it up to eleven. The book is remarkable for the inventiveness, coherence, and above all, sheer volume of ideas it presents. Page after page, the reader is presented with fictional physics, the realities (or lack thereof) of life in a virtual reality environment, the mind-twisting experience of gazing at a four-dimensional night sky, and the consequences of all this for characters and their choices.

Diaspora is not a balanced novel. Though the characters are believable and make genuine, difficult choices, they are not always the main focus. The plot takes a while to get started, and once it focuses more on a series of shorter subplots rather than one overarching plot.

Yet when it comes to its ideas and their presentation, Diaspora is the Platonic ideal which other science fiction novels can only strive towards. If you enjoy reading about the type of ideas Diaspora is filled with, the novel is an incomparable joy to read. And if you don’t, well, the novel is still bound to be incomparable.

Physics vs plot

The novel begins in the year 2975. Humanity has split into three factions:

• The most normal are the “fleshers”. As their name suggests, they are flesh-and-blood biological humans, though many have modified their minds and bodies into different forms, hence making communication between different groups difficult. They consider the gleisners and the citizens to be too far removed from reality.

• The “gleisners” consider the fleshers hopeless luddites. They have uploaded their minds into computers, which in turn are part of robotic bodies well-adapted to outer space.

• The “citizens” consider everyone else hopeless luddites, while being seen by everyone else as reality-detached solipsists. They exist as software running in virtual reality communities known as “polises”. The polises have sufficiently powerful hardware to simulate more than one second of experienced time for its citizens for each real second that passes, and hence the rest of the world passes in slow motion from their perspective (though others slow down the rate at which they experience time, either to keep touch with reality or to watch mountains erode and continents move in front of their eyes). Citizens running as fast as possible since the polises were built have experienced about 740 000 years of time, even though the polises have existed for only nine centuries.

Unlike most citizens, Yatima, our main character, is an orphan: built by the polis software from scratch, rather than being designed by “parents”. The first chapter is dedicated to detailing how this process unfolds, from the process of choosing a “genetic” code for a new mind to the orphan becoming self-aware. By describing the process visually, Egan manages to make fictional algorithms operating in abstract multidimensional space interesting.

If, after twenty pages of this, you think the plot must be about to begin, you are in for a surprise – instead, Egan takes us through the outline of a proof of the Gauss-Bonnet theorem. Here’s a sample:

Ve tried smoothing and flattening the six points [six points on the surface of a sphere that form an octahedron]. That was easy – but it made the eight triangles [of the octahedron] as bowed and non-Euclidean as they’d been on the original sphere. It seemed ‘obvious’ that the points and the triangles could never be made flat simultaneously . . . but Yatima still couldn’t pin down the reason why the two goals were irreconcilable. Ve measured the angles where four triangles met, around what had once been a point of the diamond: 90, 90, 90, 90. That much made perfect sense: to lie flat, and meet nicely without any gaps, they had to add up to 360 degrees. Ve reverted to the un-blunted diamond, and measured the same angles again: 60, 60, 60, 60. A total of 240 was too small to lie flat; anything less than a full circle forced the surface to roll up like the point of a cone …

That was it! That was the heart of the contradiction! Every vertex needed angles totaling 360 degrees around it, in order to lie flat . . . while every flat, Euclidean triangle supplied just 180 degrees. Half as much. So if there’d been exactly twice as many triangles as vertices, everything would have added up perfectly – but with six vertices and only eight triangles, there wasn’t enough flatness to go round.

(“Ve”, “vis”, and “ver” are genderless pronouns that Egan uses, since many of the virtual citizens do not have a gender)

The math explanations give just enough intuition to impart some ideas, while not slowing the plot to a complete crawl (though I have to admit that the Wikipedia page for the Gauss-Bonnet theorem 1 still looks like hieroglyphics to me).

We are next introduced to the “Truth Mines”, a virtual cave system where every known mathematical theorem is linked by tunnels that trace out the path from basic axioms to a proof (this is a monumentally cool idea).

Only some time afterwards does the plot begin, when Yatima and vis friend Inoshiro download their minds onto gleisner robots and go visit the city of Atlanta, where a group of fleshers live.

A revealing point about the novel is that though there is a plot line involving a lot of action after a cosmic disaster strikes Earth, an even more significant plot line is figuring out the physics that caused the disaster in the first place.

In addition, the novel lacks antagonist characters – the plot is very much man versus nature rather than any of the other archetypical conflict types 2. Or, to be more precise: man (and woman (and genderless virtual software person)) versus cosmic catastrophe caused by unknown physics that the characters have to figure out.

The status quo of theoretical physics for centuries at the beginning of the novel is Kozuch theory, a fictional successor to relativity and quantum mechanics in which elementary particles are the mouths of wormholes. It only gets wilder from there. Egan clearly knows a lot of physics; his website includes a comprehensive set of articles covering the basics of special & general relativity and quantum mechanics 3, in addition to an even larger set of more advanced articles 4. This shows in the discussion of physics theories in the book. If the next great advance in physics is eerily similar to Kozuch theory, I wouldn’t be too surprised.

Convincing craziness

Though Egan and his characters spend a lot of time explaining and ruminating about things, the novel never seems to fall into the trap of explaining too much.

For example, works involving teleportation, mind-cloning, or generally anything that allows minds to work like software (copied, put on hold, transmitted, etc.) often rehash philosophical debates about whether the clones are the same person as the original (and countless similar debates that are mostly about semantics).

Diaspora sidesteps these debates, wisely focusing instead on what the characters experience. When one character is paused, cloned six times, and the clones restarted in six different places, Egan simply describes the character relaxing in a virtual reality environment before seamlessly finding out his destination. This is what the event would feel like, to each of the six versions; no need for philosophical pontification about the nature of identity.

This is part of what makes Diaspora so convincing: the characters are completely at home in their strange world, and confront the dilemmas it poses like real people seeking pragmatic solutions, rather than philosophers expounding their theories. Philosophical themes are unavoidable when the setting looks like it does in Diaspora, but they come about naturally, rather than being forced. Other works –  Permutation City, another Greg Egan novel, comes to mind – are all about the philosophy, and succeed at this, but the approach in Diaspora makes for a more visceral story.

Many science fiction works seem to work backwards, as if the author had thought “I want X to happen; what do I have to introduce to make X possible?” This often leads to contorted logic, and makes the ideas serve the plot rather than have the plot illustrate the ideas.

Diaspora gives the sense that Egan worked forwards. Given technology that enables uploading and running minds in a virtual reality, what happens? If a sketch of the next great unifying theory of physics looks like this, what technology does it allow and where does it lead? Egan follows these premises to their logical consequences. This is another point that gives the novel a gripping plausibility, despite the far-future setting.

Scarcity may go, but math you will always have with you

Having evolved on some distant, finite world, they’d inherited the most valuable survival trait of all.

Restraint.

The characters of Diaspora live in virtual reality environments of almost unlimited abundance. They can clone themselves, merge with their clones, speed up or slow down time as they see fit (though the hardware their minds run on can only go so fast), and even modify their personalities. Their physical hardware is not invulnerable, especially after several polises are launched into space, but worries about physical security are mostly a thing of the distant past.

Not counting theoretical physics, most of the problems the characters deal with are therefore questions of how much they are willing to distance themselves from reality, how much they’re willing to modify themselves, and what their purpose is.

Potentially infinite amounts of experience and knowledge may be available, but in the end there are still an infinite number of worlds that “[they] would never see, never touch, never understand.” An element of restraint becomes crucial. I’m reminded of the recurring phrase “remit not paucity”, which occurs in (and is an anagram of) Permutation City. Thus, perhaps the central message is that to have purpose and identity in the face of limitless opportunities, it is not enough to choose what to do – you must also choose what not to do.

Diaspora does not present one view of how to do this. Some characters clone themselves and irrevocably change themselves in the service of a larger mission, others for more poorly thought-out reasons. A few, having exhausted over unfathomably long lifespans all that existence has to offer, or having reached the end of a lonely mission with no hope of return, opt to die.

And, true to the spirit of the book, others faced with the same choice instead choose to devote the rest of eternity to math:

Everything else from vis life in the home universe had been diluted into insignificance by the scale of their journey, but this timeless world still made perfect sense. In the end, there was only mathematics.