This is just a blind guess, but the difference may come when talking about impossibilities and/or extreme improbabilities. Empirically there might not be a way

This is just a blind guess, but the difference may come when talking about impossibilities and/or extreme improbabilities. Empirically there might not be a way to distinguish between actually impossible and merely unobserved/improbable. If an event is so unlikely that it probably has never occurred in the observable universe, how would you empirically differentiate between the two? Meanwhile I would think rationality and logic would face no such obstacle. (Naturally rationality has it's own limitations, but that's a whole new topic.)