ABSTRACT
On not simulating a universe

"What if we are just a simulation?" is an idea with a long history, from Lewis Carroll (the Red King's dream) through Raymond Queneau ("Les Fleurs Bleues") to modern cinema ("The Matrix").  It fits well with the complacent nihilism of modern culture, but now that simulation-based philosophical arguments seem to be attaining respectability (J.D. Barrow, "Living in a Simulated Universe"; N. Bostrom, "Are You Living in a Computer Simulation?") it is time to examine the ontological implications of simulations.

Contemporary simulation arguments pay great attention to the computing power needed to simulate (for example) a human brain.  I argue that such considerations are irrelevant.  Starting from some straightforward premisses about what happens when we do arithmetic, I show that from the point of view of the inhabitants of a simulated universe it makes no difference whether anyone actually ever runs their simulation.  In fact, their lives will be the same even if the simulation program is never written; possibly even if it is never thought of.  As a result some of the more science-fictional theories of recent years (such as Tipler's "resurrection-by-computation" eschatology) completely lose their point.

If we accept that the inhabitants of a simulated universe walk, talk, eat, think, fight, and have souls just like us, we are faced with a problem.  Specifically, we have a more-than-Borgesian embarras de richesse: every possible universe exists, however strange it may seem to us, and a world in which Boyle's Law is different on Thursdays exists in just the same sense as our own.

An argument that leads to such a superabundance is equally problematic for theists and for atheists and a response of some kind is needed from both.  One answer, I suggest, may lie in worrying less about the act of simulation and concentrating more on initial conditions - giving our own universe more "reality" than the ones we simulate.  But even this answer is vulnerable to paradox.

Simulation arguments raise further interesting parallels between God's creation of a real universe and our own creation of a simulated one.  Comparison of the respective roles of creator/simulator and creature/simulation should lead to some fruitful and stimulating discourse between science and theology.

Keywords: simulation, creation, science fiction, ontology, computation, possible worlds.