Yes, partly you are correct, in that in reality you cannot make any extensions and thus no assumptions. To do so is the epitome of folly, or a waste of time.
If God is beyond our understanding, unknowable, a mystery, whatever adjective you choose to use, then basically that is just saying that everything else is merely guesswork, conjecture, whatever.
That is fine to do if you have nothing better to do, but it is akin to playing child games like tag or hide-n-seek.
There actually may well be nothing to believe exists or doesn't exist, and all of this may be a huge elaborate dream, and you may wake up tomorrow and know all the answers, and wonder about the dream you had writing on ST about God, and at that point you will have then realized it was only a dream.