After reading this, it seems to me that “could” or “possible” simply means this—I have used an algorithm for simplified simulation, and it simulated X. The discussion about what makes X possible is simply a discussion about the algorithm used, and a degree or method of simplification.
“Tomorrow I can do X, or I can do non-X.” = I can run a simplified simulation of myself doing X; I can run a simplified simulation of myself doing non-X; and neither of these simulations produce an error. (Why? Because I am not simulating myself down to a neuron / atomic level. A more detailed simulation could show that with given state of my neurons, I will tomorrow decide to do X, instead of non-X.)
“The billionth digit of pi could be zero.” = I can visualize myself calculating pi to billion decimal places. But my visualization does not include the critical details, which I simply replace with a reference class “digits in pi” or simply “digits”. At the end I have multiple “possible values of billionth digit of pi” because the reference class I used contains multiple values.
In other words, “possible” means: using my imperfect information, these worldstates were not falsified.
After reading this, it seems to me that “could” or “possible” simply means this—I have used an algorithm for simplified simulation, and it simulated X. The discussion about what makes X possible is simply a discussion about the algorithm used, and a degree or method of simplification.
“Tomorrow I can do X, or I can do non-X.” = I can run a simplified simulation of myself doing X; I can run a simplified simulation of myself doing non-X; and neither of these simulations produce an error. (Why? Because I am not simulating myself down to a neuron / atomic level. A more detailed simulation could show that with given state of my neurons, I will tomorrow decide to do X, instead of non-X.)
“The billionth digit of pi could be zero.” = I can visualize myself calculating pi to billion decimal places. But my visualization does not include the critical details, which I simply replace with a reference class “digits in pi” or simply “digits”. At the end I have multiple “possible values of billionth digit of pi” because the reference class I used contains multiple values.
In other words, “possible” means: using my imperfect information, these worldstates were not falsified.
This is the exact way I think about it as well.