This phrase is heard in Parmenides', poem On Reality, and in a different form of language in the Bhagavad Gita, and in A Course in Miracles:

Parmenides:
Two paths are open to investigation.
The first says: being is and non­being is not.
It is the path of certainty, because it follows the truth.
The other says: being is not, therefore non­being is.

The Bhagavad Gita (2:16):
It is found that the unreal has no being; it is found that there is no non-being for the real. The certainty of both these propositions is indeed surely seen by the perceivers of truth.

[translation 2:]

In the unreal there is no duration and in the real there is no cessation; indeed the conclusion between both the two has been analyzed by knowers of the truth.

A Course In Miracles:
Nothing real can be threatened, nothing unreal exists. Herein lies the peace of God.

 

Why is this type of saying echoed in different wisdom teachings? They are all pointing to the same truth.

The Glimpse

At some point, through the grace of crisis, or grace for no reason, there can be a glimpse of Reality, of That what is aware, with no limitations. That which is aware, and aware of awareness, is not limited by that which is it aware of: the thoughts, such as of a "me", or the perceptions, or sensations.

If you've had this experience, you know what I am talking about. If you haven't, or it's been a while, let it sink in. Ponder it.

Awareness of Awareness, Being Aware

Let's call it "the awareness of awareness being aware."

That's a mouthful, with three "aware"s in there. But fair enough. The point is, there has to be an awareness of awareness, otherwise we are talking simple animal awareness, blind to itself as it were.

And the "being aware" part must be added, because what is awareness aware of, besides the awareness-ing? It is not a thing, but the very most fundamental fact of Being... indeed how can one be aware without being, and how could one be without without awareness? That would be a totally useless and unknown be, and for any practical purpose, so to speak, not being.

Not Being is Not

Yes, so one cannot be, without being aware of it, nor be aware without being. They are fundamentally inseparable. If you think about it deeply, how could one be aware of not-being? It is a contradiction. It is a concept, and image, only – and a concept and image that we are aware of, as an element of our mind. It is not nothing. There is awareness, and there is an awareness of something: a something called "non-being". It is similar to the case of claiming there could be a separate reality. How would you know? It is pure speculation, fantasy, linguistic play, without any practical bearing on what we are pointing to here: being is, non-being is not.

Pure Awareness

They call this experience the experience of "pure awareness". It's just a name. Don't get caught up in names. It is not a thing, nor a state.

You could see the seeing of pure awareness a stage in one's development, as it were – so-called "spiritual growth".
You could see it as a pedagogical tool, for helping those new to this, see beyond their  conditioning, their social learning.

(And please do not make Pure Awareness into a fundamentalism – we are not wanting to create a religion here! Pure Awareness is not an abstraction, not just an idea, not just a concept: it has attributes, such as Beauty Love, Truth, that are unopposed, unchanging and inseparable).

The whole point is that it's a dismantling of false assumptions and a rebuilding of our life on solid ground. An attunement. An "embodiment" (without a separate body) if you will.

Ultimately, pure awareness not separate. That's the whole point: to see Consciousness in all, in all experience, literally. Rather than living as an object among objects, a thought, a person, a body, a man, a woman, a name, identified as such. That is hell.

But to see Consciousness in all experience is the "Advanced Course", relative to the Glimpse of awareness. It is the life mission so to speak, the "Self realization", unending: what I call the "Infinite inquiry".

That is, having a Glimpse or an enlightenment experience, or an awakening, or whatever you want to call it, is just the beginning. Many "residues" of ignoring reality remain – a shitload (pardon my Greek) of erroneous beliefs and habits gathered over time. We are not fully, and may never be, fully "established".

In fact, if you meet a fully realized being, let me know. I've never met one. It's all rumors at this point...

Don't Mind Creation

No need to wander among countless creations, constantly changing, or wavering amongst the many or the few,
or stuck in the mud,
or fearing where it’s going, or from whence it all came…

Pure existence itself, that which must Be, the innermost, must therefore
Fill all.

When it is clear the phenomenal has its root in the non-phenomenal, the chase in the phenomenal has its driver removed, or given a fatal blow, and starts to lose steam. This is not a bad thing.

This is not saying something against or about creation; creation goes on. But this Seeing, this knowing oneself,  steadies the course. Saves much time.

This is called "the direct path".