If it’s finite you don’t know how many entities there are in it, or what proportion of them are going to “trade” with you, and if it’s infinite you don’t know the measure (assuming that you can define a measure you find satisfying).
These are baby problems for baby animals. You develop adequate confidence about these things by running life-history simulations (built with a kind of continual actively reasoning performance optimization process that a human-level org wouldn’t be able to contemplate implementing) or just by surveying the technological species in your lightcone and extrapolating. Crucially, values lock in after the singularity (and probably intelligence and technology converges to the top of the S-curve) so you don’t have to simulate anyone beyond the stage at which they become infeasible large.
You don’t need certainty to do acausal trade.
These are baby problems for baby animals. You develop adequate confidence about these things by running life-history simulations (built with a kind of continual actively reasoning performance optimization process that a human-level org wouldn’t be able to contemplate implementing) or just by surveying the technological species in your lightcone and extrapolating. Crucially, values lock in after the singularity (and probably intelligence and technology converges to the top of the S-curve) so you don’t have to simulate anyone beyond the stage at which they become infeasible large.