Well, consider this. Say a guy comes along whose birth fulfills hundreds of thousand-year-old prophecies (which he obviously couldn't have a hand in). Then, say this guy starts healing people miraculously just as other ancient prophecies said he would. Say, also, that this fellow says "I am God, and here's how you'll know I am who I say I am: they're going to kill me, but three days later I will rise again. I am telling you before it happens so that you'll know I am [who I say I am]." And then he does just that: tomb is empty. And, say there are at least 500 witnesses to this resurrection. And then suppose the entire world bases their measure of time on the birth of this one guy (what year is it?).

If this guy really is who he says he is, then wouldn't you accept that what he said was true about "the beyond" was true? How else could we know what's true about "the beyond" unless someone came from there to tell us about it? Neither you nor I can ever live long enough or travel far enough to experience every fact of reality to the point where we can say something true about "everything." We must rely, then, on someone beyond--someone who transcends our limitations. Say this someone was trying to figure out how he could prove to us convincingly that he was telling us the truth - "I know: I'll defeat the one enemy that none of them can: death itself. Surely, that will convince them." Think about it. What else could he have said or done that he didn't already do?

And if all that is acceptable, then we can know what's true about 'the beyond' simply because he has told us.

"The secret things belong to the Lord; but what he has told us belongs to us, and to our children, forever."