Permutation City by Greg Egan
My brain lurched about eighty pages in, the moment the "dust theory" fully landed, and it blew my mind. Ever since, it has led me to spend more time thinking about it than I spent reading the book itself, which is the highest and most disturbing compliment I can pay a novel.
The idea is this: if human consciousness is capable of being computed, a Copy is as conscious as a person. It does not matter what order the computation runs in, or where, because subjective experience doesn't depend on the permutations that give rise to it.
A mind could assemble itself out of dust motes scattered across the universe and astronomical time, asking itself where and what it is, and still, from the inside, feel like a continuous life.
It is the best dizzying mind-candy I've encountered and a serious and troubling philosophical argument. The personal identity problem is dramatized with real teeth, and abstract arguments make mincemeat of common sense.
My snag: I just couldn't accept one of his core ideas about virtual worlds being run in a distributed fashion through dust, with seemingly no communication or control of the processing. I had more problems suspending disbelief over the central tenet of this book than almost anything. The second half hinges on it, and I just couldn't get behind it.
The human material is thinner, as usual with Egan. The characters are not particularly interesting, and the back half, once we are inside Durham's built universe with the Lambertians, smacks a little too much of wish fulfillment. It becomes more of an action movie with no scientific explanations of what's going on, a physics-free playground.
The ending flips the perspective from the created to the creator, where the aliens come up with an alternate explanation for their existence and out-reason their makers. And it is not just a matter of the Lambertians out-explaining us. The whole edifice collapses on the logic that there never can, and never will, be Gods, unless the anthropic principle kills Tinkerbell.
I finished it slightly destabilized about the nature of my own existence. The whole VR versus immortality thing is quite distressing, which, honestly, what more do you want from a book?
Hard, cold, brilliant. It changed my view of VR, and it will expand your mind.