Oneness
Oneness is not experienced as a something, an object of perception.
It is known by being it, directly, without subject and object
duality. One is aware of one's body as part of all appearance,
of all the perceived universe. All appearance that one can perceive
through the senses is perceived as one and whole; there are differences
but no partitions. One, in fact, feels as if the whole universe
is one's body. Everything is one, Pure Being, which is the ground
and nature of everything. There is no localization of consciousness
in the body. The body is completely in unity with the rest of
physical reality. (The Pearl Beyond Price, pg 456)

Although we say that it is difficult to come to a place where
we perceive the Supreme reality, we also know that there is no
method to achieve this, because employing a method assumes that
there is someone there, someone who is trying to get somewhere.
By its very nature, method indicates a belief in separateness.
So there is no technique, no method, no understanding that will
precipitate the perception of oneness. If you do anything to get
there, then you must be seeing yourself as a separate person,
acting according to that separateness, and trying to get oneness
-- which is impossible. Still the perception of oneness does happen,
because it is a fact, it is the reality. It happens when we relax,
when we abandon our beliefs and our ideas and our defensiveness
and our fears, when we do not need to constantly be protecting
ourselves and pushing away the outside, when we are not busy enhancing
ourselves and thinking of ourselves. (Diamond Heart Book 4, pg
105)

It is living the true human life which allows the possibility
of the arising of the perception of oneness. You have to live
a life that is conducive to the experience of oneness, a life
that doesn’t resist that perception. You need to live a
life that doesn’t depend on separateness, but on oneness,
although you might not yet experience the oneness. (Diamond Heart
Book 4, pg 105)

Oneness and mind
As your mind develops, and has concepts, it conceptualizes an
entity that is you, that is based on the perception of your body.
Before that happens, there is oneness. The oneness is nothing
but the experience of reality without the intervention of the
mind, without concepts. The oneness is nonconceptual reality.
What are concepts? Concepts are nothing but boundaries. (Diamond
Heart Book 4, pg 114)

Oneness and Personal Essence
The realization of both the condition of oneness and that of
the supreme Personal Essence now shows the deeper and objectively
true relationship between Being and the person. As Being, one
experiences oneself as all of existence, boundless and eternal.
One is a oneness, which is the universe, but also beyond it. There
are differences and varieties in the universal oneness, but no
separation. As the Personal Essence one is a pure person, a Personal
Presence of eternity. But one is continuous with the oneness,
as a form coemergent from Pure Being. One perceives oneself as
a cell in an infinite body. (The Pearl Beyond Price, pg 457)

Oneness and vulnerability
When you are aware of oneness, when you see that you and everyone
else and everything else are completely one, the vulnerability
will not be seen as a disadvantage at all. The moment your vulnerability
is complete and you are aware of oneness, there is no fear. When
you are completely vulnerable, completely not separating yourself
from anyone or anything, when you know that you are the oneness,
that your very nature is the unity, is the supreme reality, then
you know that in your deepest, most intimate, absolute nature
and identity you can't die --nothing can happen to you. You are
one-hundred-percent invulnerable. (Diamond Heart Book 3, pg 200)