It is fairly obvious that there is something beyond our conscious mind, and there are many who try to consider what is beyond that. Even in mathematics there are those who are not satisfied with infinity, but wish to discuss infinities of infinities. Beyond the beyond.
The exercise of contemplating nothing, if nothing else, should make it clear that there is a limit beyond which we cannot go. If there could be anything beyond that limit, it could only be contemplated in terms of the effects it might have on the immediate beyond, which in turn could only be understood in terms of the awareness of that portion of reality with which our minds can be associated.
Our minds become aware of reality because we are a part of that reality. We first become aware of our body which is part of what we call the physical universe. Not only do we become aware of it, we actually learn to control it in some limited ways. I can, after all, suck on my thumb if I want to, even though I don't know how I exercise such control. I cannot, however, exercise direct control over the rest of the physical universe by just "willing" to do so, even though it is made up of the same "stuff" as my body. Despite the claim that some are able to exercise some direct control over matter other than their body, l.e., psycho kinesis, I tend to be skeptical, though I cannot rule out the possibility. In any case, the ability of the mind to exercise direct control is limited to a small part of the material universe.
Similarly for the non-physical aspects of mind. They too are part of the reality that contains other minds. Although there are claims similar to psycho kinesis, that there can be direct mental communication, i.e., clairvoyance, Divine Revelation, etc., I tend to be skeptical as well, though here too, I cannot rule out the possibility. Most of us communicate with other conscious minds by manipulating the physical universe which is common to all in such a way, e.g., by writing or speaking, that the association with this common reality allows the identification of the conscious mind originating the communication.
I do not consider the physical universe to be beyond my consciousness. Indeed, I am not only conscious of it, I am a part of it. If I can become conscious of any part of it, there is no logical reason to believe that I could not become conscious of any other part of it.
I am also conscious of the reality which includes other conscious beings and non-physical entities as will, and thought. Although I cannot deal with anyone's consciousness directly, it is not really beyond me to know something about their consciousness indirectly through the medium of the physical universe we share. In any case, other conscious beings are no further beyond the reality I know than I am.
Sooner, or later, the question arises: where did all of this come from?. There are only two answers to that question. Either it was created, or it always was and always will be.
Although that question could be asked with the inclusion of non-physical realities of will, consciousness, thoughts, feelings, etc., it is usually asked and answered with respect to the physical universe alone, and I will so restrict my comments here.
In the first case, all that exists is postulated to be the result of some existing entity that has a nature that is different from the physical universe which it creates. Thus there is no inconsistency of the physical universe having a dual nature: i.e., having a beginning and probably an end, while at the same time, having the attribute of infinite existence, e.g., always was and always will be. There is a Reality - a Creator - that created the "Big Bang", or the "Big Bang" created itself, which implies it had to be before it was created.
Choosing the second answer to the question, in addition to the defect indicated above, leads to other inconsistencies as most of the attributes theologians usually ascribe to the Creator, the atheist must ascribe to the Physical Universe. I have no serious quarrel with most atheists because it seems to me that most of them are merely denying the validity of some particular conception of God. Most of them that I have known will acknowledge in some way that there is a power greater than themselves, and greater than the universe, which are among the most primitive concepts of God. After all, we are talking about a reality here, no matter how well, or ill-conceived, it may be, or what name it is called.
An interesting way to look at the difference between a theist and an atheist is from a psychological point of view. Since it is reality that is at issue, one of them must be nuts. Either the theist is hallucinating what he believes to be reality, or the atheist is denying the reality because it does not conform to what he believes it ought to be. The differences between them are usually not viewed in such stark terms because there is a common physical universe which mitigates their differences. The differences, however, cannot be entirety obliterated, so that the answer to the question: where did it all come from? has some serious psychological significance, and at the very least, has some effect on thinking.
Although slightly off the current topic, I will comment briefly on solipsism since it frequently arises in discussions of existence. The claim of solipsism is self-refuting. Actions speak louder than words. The claim to being the only existing conscious entity is refuted by the attempt to communicate in making the claim. In any case, solipsism is a lonely existence. Perhaps those who try to retreat into such a position are merely asserting that they wish to be alone. That's OK with me. If, and when, they wish to communicate with me, they would have to relinquish solipsism since I do not like to associate with anyone who will treat me as if I didn't exist. I think that's very rude.