[zeroca]

When you are sitting at home and are asked, what is outside the wall, which hasn’t window, you answer: “neighbor’s garden”. You don’t see it but you know it and can directly check it by coming out and seeing it. When you are asked what is inside the electrical cable, which is covered by isolation, you can answer “metal” and you know it and can directly check it.
When you are asked is there current in this cable, you don’t need to check it directly. If you see both ends of it unconnected, then you are sure that there’s not current in it, or if the cable is the part of network, you can check it by lighting the bulb or turning of some el. device;
So briefly you can prove credibility of any event by checking it direct or indirect way. But we are deprived to check by any mean what is beyond the any furthest spatial points we can imagine, so we should guess, and it comes to two alternative answers: either something, or nothing and I don’t care much about either of them: they both are here at hand…

Regards,
zeroca.