If you are an empiricist you can't be sure about anything, you can't be even sure that your theories are describing what 'is' the world, they are just a way to look at it.

If you are rationalist, you would believe that there are some kind of innate features of your brain, now where those features came from?

You can't compute the next tick of the entire universe using a process that is contained within it. That would be like saying a single page of a book can contain the entirety of the book (without changing the size of the letters, obviously). It doesn't fit.

Here's one piece of evidence out of thousands more. Consider that the psychedelic effects of LSD can be prevented simply by blocking 5-HT2A receptors in the brain [1]. This is what you would expect if a psychedelic experience is a biochemical phenomenon occurring in the brain, like that sparked by caffeine. A more powerful and much more interesting one, yes, but not something that requires talking of "god" or "universal understanding".

[1] https://blogs.scientificamerican.com/scicurious-brain/httpbl... (search the page for "block the 5-HT2A receptor")

I've been there -- too tired or busy to write out a proper response. Lately, I have been thinking that not responding is better in such cases.