John 20:29

Jesus saith unto him, Thomas, because thou hast seen me, thou hast believed: blessed are they that have not seen, and yet have believed.

Seeing is believing and no thing is believed that isn't seen, that is judged* to be true (I see the truth of it), thus shaping our expectation. How then can anybody ever believe without seeing?

Well, in order for there to be belief, something needs to be seen, and if it is not the truth of what is in question, it can only be the authority of the asserter. In how far is it blessed though to believe someone else, rather than understanding the truth of the matter oneself?

I doubt that Jesus had something like 100 pages long mathematical proofs in mind, and I'm not even certain whether that example qualifies, because it is a sort of bliss to see the truth of such a proof. Of course, in all likeliness not even the author does, but rather trusts his own authority to have put everything correctly together.

No, I think the truth in question is a particular one, namely the recognition of a moral duty. When a moral duty is towards God, its recognition is always bitter, because it means that God has requirements before he'll help us. But when an accepted human authority imposes a duty on us, we feel trusted and important and are keen to prove ourselves.

* My technical term for these kind of judgments is insights. [Sounds correct to me, like these blue shoes and not this blue shoes, I mean, kind of simply means of one kind, i.e. it acts as an adjective.]