All reality is interpretted through neuronal constructs. Why is some reality more real than other reality? Because it can be tested in the "real" world? What world is not subject to the filter of neuronal constructs, exactly?
I am not arguing that nothing can be known. I am arguing that everything can be, as long as it is remembered that all knowledge and all reality is subjective, at some level at least.
I fully see your point in how all of us mentally exist in a constructed "reality" thats prone to varying degrees of subjectivity. Models of reality, be it dreams, hallucinations, or contructs generated from the stimuli of our sensory inputs, have similar "concreteness" at the level of neurochemicals and action potentials. They are all equally real at that level. But then I see this as meaning we'll never be sure of knowing something completely and absolutely. We have to be able to identify the providence of whats generating those cascades, to discriminate the external from the internal, the blips from the constants.
Ergo, the importance of being able to reproduce a phenomenon, preferably with tools and methods acting as extensions to our own senses, in order to establish some confidence in its being substantial and of its providence. Our enhanced ability to influence, control and manipulate external reality means that we will be better off to favour some models over others. The dialectic we have in the scientific method isn't 100% accurate but I think that its continually refining our models.
I can see your point if you're arguing the following: That if we're never mentally open to exploring for the spiritual or any interaction with the divinity then we're likely going to misperceive it. Our current paradigm can work fairly well at one level, but still be limited so that it may not on another (like classical newtonian mechanics vs quantum mechanics). Maybe personal internal experiences are the only way to interact with a postulated spiritual/divine "reality". I'd say that leaves us with no solid evidence (hence the need for faith).