I think many serious religious people would answer your question with the concept of "revelation", @
Pussy Galore. For instance, my uncle believes that the truth about God and his essence has been revealed to him throughout religious history and through his own spiritual experiences. Most religions are founded on a particular prophet's personal revelation (for instance, Mohammed) or on someone's mere existence actually being (part of) the essence of the revelation (Jesus Christ).
I myself haven't experienced that moment of revelation myself so I can't truly speak for those who have or those who believe in (certain) revelations that are claimed to have happened by many people throughout history, but I think that's an important core for many mature people's religious identity.
As I know you like to be challenged and humbled by arguments and knowledge, I'd like you to think about this quote by C.S. Lewis (who I know Yoda is a big fan of), @
Pussy Galore. It takes some of the concepts of knowledge, doubt and uncertainty that you used in your first post and throws it right back at us, atheists:
"Supposing there was no intelligence behind the universe, no creative mind. In that case, nobody designed my brain for the purpose of thinking. It is merely that when the atoms inside my skull happen, for physical or chemical reasons, to arrange themselves in a certain way, this gives me, as a by-product, the sensation I call thought. But, if so, how can I trust my own thinking to be true? It's like upsetting a milk jug and hoping that the way it splashes itself will give you a map of London. But if I can't trust my own thinking, of course I can't trust the arguments leading to Atheism, and therefore have no reason to be an Atheist, or anything else. Unless I believe in God, I cannot believe in thought: so I can never use thought to disbelieve in God."
The bolded part rings especially true to me, while I believe the last part is a bit of a leap he probably consciously made to hit his argument home. I think it's a very humbling bit to deeply think about.