Challenging the First Article of Faith
The first Article of Faith of the UCTAA is as follows:
"1. The existence of a Supreme Being is unknown and unknowable.
To believe in the existence of a god is an act of faith. To believe in the nonexistence of a god is likewise an act of faith. There is no evidence that there is a Supreme Being nor is there evidence there is not a Supreme Being. Faith is not knowledge. We can only state with assurance that we do not know."
The explanation seems only to argue that the existence of a Supreme Being is unknown, and that no one could justifiably say that they know for certain whether a god exists or does not exist.
However, the explanation provides no reason to believe that the existence of a supreme being is unknowable. To say that something is unknowable is to say that no evidence would ever be sufficient to convince someone one way or the other.
This seems a little extreme. If letters of fire appeared in the sky over populated places all over the world, and a god started talking to everyone on the planet, (explaining, perhaps, why he didn't do this earlier), I would take this as pretty conclusive evidence for the existence of god. Applying David Hume's famous miracle test, if the probability of it happening by chance was really very, very high, then we'd have good reason to believe the alternative explanation; that god exists.
Of course, no amount of evidence can prove the existence of anything absolutely. In this sense, we could never claim to "know" that god exists. But this sense is trivial; similarly, I could never claim that I absolutely "know" that my salt and pepper grinders exist. I presume that the Articles of Faith are not using "know" in this sense.
So why claim that the existence of god is unknowable?