A simple clock simulates the evolving state of a complex world, when interpreted via a world-describing playbook or movie sequence keyed to clock ticks. Even the clock is superfluous, since an external observer can read the book or watch the movie at leisure. Mathematical realism, a philosophical position advocated by Plato, addresses this problem's vexing intangibles. Just as physical objects are seen by the senses, mathematical objects like numbers and shapes can be observed via abstract thought, to reveal objectively verifiable features. To Plato, mathematical concepts were as real as physical objects, just invisible to the external senses as sound is imperceptible to the eyes.
Computer simulation brings mathematical realism neatly full circle.
Plato's unaided mind could handle only simple mathematical objects, leading do such dichotomies as the idea of a perfect sphere compared to a mottled, scratched marble ball in the hand. Computer simulation, like a telescope for the mind's eye, extends vision beyond the nearby realm of simple objects, to details of distant worlds, some as complex as physical reality, potentially full of living beings, warts, minds and all. Our own world is among this vista of all conceivable ones, defined by the abstract relationships we call physical law as any simulation is defined by its internal rules. It defuses various worries about intelligent machinery. Some critics argue that a machine cannot contain a mind since a machine's function is entirely an outside interpretation, unlike human minds, which supply their own sense of meaning.