Permutation City is a 1994 science-fiction novel by Greg Egan that explores many concepts, including quantum ontology, through various philosophical aspects of artificial life and simulated reality.

It focuses on a model of consciousness and reality, the Dust Theory, similar to the Ultimate Ensemble Mathematical Universe hypothesis proposed by Max Tegmark.

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.

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).

He explains to her that intelligent life has arisen on Planet Lambert in the form of complex swarms of insect-like eusocial beings, evolved from Maria's original Autobacterium hydrophilus.

He wishes 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 Lambertians.

He believes this is necessary because he has 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.

They discover that the combined intelligence of Lambertians has exceeded that of Permutation City; as such, the TVC universe is being overwritten into a system existing solely as a byproduct of the self-perpetuation of the Autoverse.

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 preferentiality over their own newly formulated theory.

Maria convinces a reluctant Durham to come along to a new universe, pledging to work with her to discover the underlying rules that governed the Autoverse's takeover of Permutation City.