Hi Erkka, on the urw-forum you conclude you must be agnostic.. But that might be just a step away from gnostic instead of the opposite. Because, what is the thing that experiences, what is the I that 'knows' things to be true or false, or judges them? It seemed to me you succesfully used 'logic' [which is what? What are it's 'rules' based on?] to falsify the omnipotence of the brain [or it's constructs] but still choose to use the quite nihilistic label of a-gnosticism for your state of understaning [or 'gnosis' quite paradoxally ;)], not being able to know things.. or that this ability would even matter anyhow. Which seems to contradict your obvious motivation of knowing / understanding things better, or the idea that you could make any progress this way.. Gnosticism at it's core is about the liberation from the 'laws' of nature. Which is quite relevant in the human evolution nowadays where our mainstream education/newsfeed is mostly aimed at keeping us in the dark and 'law'-abiding. Because if you can break them, they're not laws but agreements [at best], natural 'laws' are related to [human] consciousness, not the other way around, even the scientific method [if applied honestly] points quite clearly to this idea.
Godspeed.