Are You Living in a Computer Simulation?
Nick Bostrom · 2003
"At least one of three propositions must be true: civilizations almost never reach the technological stage capable of running ancestor-simulations, or those that reach it choose not to run them, or we are almost certainly living inside a simulation ourselves — and there's no principled way to rule out the third."
Bostrom's argument doesn't claim we are in a simulation — it's a trilemma. If any future civilization eventually gains enough computing power to simulate entire conscious populations of their ancestors, and nothing stops them from wanting to, the number of simulated minds would vastly outnumber the one original population by many orders of magnitude. So if you accept that such simulations are possible and that at least some civilizations would choose to run many of them, simple probability suggests an average observer picked at random is far more likely to be one of the many simulated minds than the one original.
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Large Number Coincidences and the Anthropic Principle in Cosmology
"Several of the universe's fundamental physical constants appear implausibly fine-tuned for the emergence of life — but this isn't necessarily evidence of design, because any universe where observers exist to notice the constants will, by definition, have constants compatible with observers existing."