Back at you.
The point wasn't to prove 1 + 1 = 2. I know people have done that. The point was that it shouldn't be necessary in this discussion to prove it, any more than it is necessary to prove that you don't know what you can't know.
Back at you. The question I addressed was the causality question. I merely answered your challenge for proof of 1 + 1 = 2. Again, countless people more intelligent than you or I have wrestled with the question. They didn’t throw up their hands and say “We can’t know.” They attempted answers. Obviously none satisfy you. That does not mean you are right and every believer is wrong. You establish that you know the complete set of unknowable things or can prove the membership of any and all items in that set.