I feel like this type of question inevitably spirals back to "why is there something instead of nothing", there is not proof that all of reality is a single unity. We could be experiencing multiple realities at once, the human brain and its senses have been proven time and time again unable to accurately depict the world around us. Personally I believe there is something after death, you can call it a cope if you like but I believe in the soul and its immortality. I don't think unending unconsciousness is all that terrifying a prospect, it's merely a dreamless sleep something people experience all the time. I'm unsure what happens after death as all people are, perhaps we reincarnate, maybe there is a judge who decides if you go to heaven or hell, maybe we're transported to a different reality entirely, maybe none of these are true. Ultimately you shouldn't be wasting your time with questions like these you'll drive yourself mad, just lead a good life whatever that means to you and accept death with grace. Don't go out whimpering and pleading for another day, accept that everything comes to an end.
"Why is there anything rather than nothing" is basically the entire foundation of Taoism since it turns that on its head and explains everything is fundamentally nothing. Nothing+something being two sides, but one coin.
In my personal experience the truth is found before rational thought takes place. It is in pure being. Pure being itself can't be wrong, which is why if I said "you don't exist" you'd instantaneously be able to ascertain that is moronic. How? You could have done this without some oldass ancient figure inventing "cogito ergo sum". So why and how is that?
Because that pure being precedes all belief, thought, concept, and ideas. "Stupidity" is something done by thoughts. "Belief" is something done by thoughts. Pure being precedes thought and itself cannot inherently be a belief as a result. Only what is applied TO it by thought can be belief (or "faith").
If you answer all questions precisely as you can verify as fact by direct experience, in the same way as you can verify you exist, you will find what is real.
Initially things appear to be solipsism. It isn't. Space and matter are not things you know by direct experience. Example: If you had no senses whatsoever would you know of a space or matter? No touch to even feel your own body. Your direct experience is not that you move through space or that you see matter, but that the EXPERIENCE of sight and EXPERIENCE of the sensation of movement is taking place. That is your direct experience. "Other people" as such only seem separated by space which you have never verified is there independently of mind, only perceived in awareness. No space = no here or there = no separation.
In your direct verifiable experience you have never experienced any time when you have not existed, you have never existed in any moment but the present (memories of the past are recalled and experienced in the present moment where you always are), you have never known more than one mind.
Consider that these seem close to ideas found in nonduality. The facts of pure being align. It claims:
1) Your true self (the pure "beingness") has never not existed because it is all things. Your own self (thoughts, emotions, identity) is an appearance which happens IN the pure being that is awareness... That pure beingness, it was never born and never dies(/died).
2) There is only one mind with no spatial dimension that encompasses all reality including all people such as you and others (not solipsism from the relative level, think of it as "God's mind" with our selves being limited parts OF that).
3) The only true time is the now. The passage of time happens inside awareness.
...
So you see the similarity. It requires both deconstruction of thought and assumed belief to get as close to a state of pure being-ness as possible.
