What demonstration? You just said you are not expressing anything.
I am giving a demonstration of two things and then two more things. The words two and four are unnecessary in the process.
Just saying something like me being irrational doesn't necessarily make it so.
Well stated. Do you therfore retract your claim that I am being irrational?
What is irrational about not being able to see Spirit?
What is rational about claiming a spirit exists if you cannot demonstrate that any spirits exist?
Make sense of the world without first presupposing God.
Disproving other hypothesis does born in any way bring us closer to yours. Even if every other conceivable hypothesis could be refuted you must still prove your claim correct or there is no reason to accept it. It is beyond human epistemology to say what if anything caused the big bang and at least since then the universe has run on mundane physical processes to the degree that we can determine how the universe runs at all.
You assume that God cannot be demonstrated to a reasonable degree to exist.
I assume no such thing. In fact past experience has led me to believe that no theistic/spiritual/metaphysical claim can be adequately demonstrated. That is no guarantee that none ever will but the sheer number of directly contradictory claims and the absolute lack of physical evidence of any kind leads me to be somewhat skeptical.
You are not a necessary being.
Au contraire from my perspective I am the only necessary being (assuming even I exist which would explain why my nose itches sometimes) and I cannot be completely certain that you exist. I am prepared to accept that you do since my perceptions woild.seem to indicate that you do and because I enjoy these conversations and they would be less enjoyable if they were completely one sided.
making sense of origins, morality, existence?
Origins: I don't know why or how the big bang started and that is the earliest event we have observable evidence for. That means we cannot know how or why it began or even if how, why or began are sensible terms to use in this context.
Morality: morality seems to be a learned behavior. Viewed in purely anthropological terms it would seem that working and living together helps pur species survive and reproduce and so we all enter into the social contract as an evolved behavioral trait. Even if there is more to it than that this is still technically true so if you claim that it is more it is up to you to prove that it is anything more.
Existence: I feel as though I exist and other stuff would also appear to exist. These feelings and perceptions may or may not be illusory but even if they are I can still make observations and learn about my perceived reality and so I accept reality prima facie purely as a convenience.