You could see this like a perception, a ''sense'' that you could add to the 21 or 33 identified scientifically (if you like science things and scientific realism)...
Take for example depersonalization or derealization, in it, you lack completely of that sense of presence (habitually also have undesirable symptoms, such as excessive ruminations, etc.), and this was attributed to a certain overactive part of the brain (I heard) (like when you think fast when seeing a lion watching you really meanly in the wild, but you're not in chock, et cetera..)
Then, a philosophist's way of thought (not the one's who wrote like Nietzsche, Camus, etc...(which established something to think from for stability or those just didn't completely detach and stopped onto those certain degrees)). The way of thought can migrate into this non existence, notably when you begin to be neutral fondamentaly on solipsism, memory/chronoception, et cetera, a full analytic way without any beliefs... Though that can reason easily with any given basic principles (types of realism, et cetera)
Then, there's the spiritual enlightenment such as in oriental religions and ways of thinking. Which would be like a step further (or a different turn or wanting, since traditions before Buddha) than the philosophist's because you did the same to your senses, you realized that destroying your beliefs made a certain detachment from ''seem'' (not making it absurd, just neutral over other possibilities) and pursuid/applied the thing for your seemingly physical existence, it being the last thing that remains. Thus process taking lots of time. Though, it is said that there is also the same outcome for maintaining beliefs, just not caring, and focusing on senses (like balance/spinning, tantrism, meditation/mind, pain like sadhus, et cetera)
One is attached to reason and presence from its before, the other for religious and empty fullness of detachment, and other examples.
In a scientific realism, it'd be the neurones and memory that'd react throughout a certain variable of time, constant evolution from a thought system to another. From the perception of circuits of neurones, like we perceive time, and other senses. We ''exist''. In physics, we aren't much more than a photon and this **** is huge, there's also string theory... (well all science is theory, but to understand perceptions and predict by them, understand, et cetera, it's a great tool to describe and it fulfills religion's place for some...)
In a solipsist way of thinking, it is seemingly uncertain imo. In an absurdist way of thinking, it can be anything that can be it in a way that is or isn't in an absurd or not; you decide. In a more oriental way, if I'm not mistaken, you are a part of a bigger thing (soul, but not really; you have to give it back after a time through existence, unless you're an untouchable in hinduism? Anyway, if you are able to in one life, if I remember correctly, you are a ''buddha'' in one of the buddhisms... sorry for not remembering and for keeping the writing)
I'll say that nothing is sure, everything can be from a person's reality or from another's (beliefs, irrefutable in its basics(no contradictions with beliefs or unknown one's of the individual), even it'd be an absurd view)... Now, you decide what you'll think and from where to start if you can. Pure speculations, as everything, sorry for my poor english and notice that I could have continued for hundreds of pages if was informed in known belief systems or decided to put all that was relevant..
It is the first real question I asked myself, it was in 9th grade two years ago.. coming back from Canada's Wonderland at 9-10 PM in a school bus (for long distances), talking with friends tired as ****... Got to 30 minutes in and yeah.. no conclusions, it's just mysterious, the question is a real circle since by science, we couldn't understand, and how could neurons from others perceive a somewhat something? How the thought? I wasn't into philosophy then, it didn't affect much, but talking about those things felt ******* great!
What is aware of this? :/ believe. Omniscience or a ''higher'' is a relatively hard concept to work with or on which I find there isn't much to do with... Live in full naivety, be spiritual like the hippies were (I don't know if modern day hippies is hippies, but you know what I mean), it's always better to live by the senses than by total reason (or killing its possibility), stop where you feel comfy, if not, it's a dead end where many roads unveil on your back, from which you are half able to be in... Also, while omniscience treats a ''before and during'', vacuity seems to cover the future or existence... just sayin.
(I personally will stay as I am now because of depressions, dp, dr, mild anxiety, etc. and I will create a belief system after that, might think about a more neutral one that talks about senses and perceptions more, or another absurdism-like philosophy... (just for myself.. a main ground already structured could be beneficial late... when I'm not this sleepy; I've slept less than 3 hours last night and the one before, I could think in a more structured and ok way, so this could have been a good reply..))
just me at 4 am, saw this, the text might be wrongly structured or might be atrocious to my eyes or yours, but yeah :)
I'll correct it if I come back not like I am now..