(1) the human species is very likely to go extinct before reaching a “posthuman” stage;It sounds odd and is definitely counter-intuitive, but the logic is sound. I think that they can be re-written a little for clarity.
(2) any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof);
(3) we are almost certainly living in a computer simulation.
(1) there are no beings capable of creating a computer simulation of sentient lifeOr, to put it in grand theological terms.
(2) there are no beings capable of creating a computer simulation of sentient life, who also have the interest in creating such a simulation
(3) we are almost certainly living in a computer simulation
(1) there is no being capable of creating a universe with sentient beingsEven just putting it into those terms makes me feel as though there's a fault somewhere in the logic, or that I've engaged in some trickery. It reminds me of the classic formulation of theodicy.
(2) there are no beings capable of creating a universe, who also have the interest in creating such a universe
(3) we are almost certainly living in a created universe
Only two of these are true.The simulation argument appears to be a negative expression of the same form. With that sense of structure in mind, let's abstract it some more.
(4) God is omnipotent
(5) God is omnibenevolent
(6) There is evil in the universe.
Consider an act (A) which is conceivable but just a little bit beyond our capabilityOr perhaps in the very simple form, "If there is an agent who is willing and able to perform (A), then (A) has almost certainly happened."
Only one of these is true.
(1) There is no agent capable of (A)
(2) There is no being capable and interested in (A)
(3) There is almost certainly (A)
When (A) is conceivable and just a little bit beyond our capability, we're more likely to take the argument seriously. However, if we define the act (B) as something far beyond our capacity to imagine or achieve then we have a hard time with the whole thing. In the very simple form, "If there is an agent who is willing and able to rebuild the universe out of subatomic matchsticks then it has almost certainly happened." If we can imagine a posthuman technology capable of creating a simulated universe, why can't we imagine a being (posthuman, transhuman, transcendent, or other) capable of subatomic matchstick constructions?
In its complex form, the simulation argument sounds all well and good, but with your friend and mine, the reductio ad absurdum, it starts to fall apart. I'm not convinced that it's a fatal flaw in the argument, but it's much less convincing at the far end of the scale.