Sometimes people can be put off by the talk of ‘oneness’ in religions or philosophies for which non-dualism is a central tenet. It can appear on the one hand (no pun intended) like so much hippie-dippy woo- which seems so alien to this world of immense suffering and constant conflict. On the other, it might appear to threaten people’s deeply held sense of their own individuality, or self. My own understanding of this (coming of course from a particular understanding of a particular variety of a particular non-dual spirituality) is as follows;
The oneness doesn’t refer to a numerical oneness. Number as well as every other distinction is appropriate only to relative existence, or rather, to the ordinary everyday consciousness that differentiates, abstracts and analyses (for very practical reasons to be sure) the phenomena of basic experience.
This oneness is not some abstract or transcendental idea. It is absolutely real, absolutely present. In fact, next to it what is unreal is/are those duality/ies that map out our lives and beliefs about ourselves and the world. These are unreal in that they are derivative and relative.
Nor is it a case of there being a numerically singular giant mass where all differentiation disappears. This latter may be a stage in the perpetual transformation of existence, such as is depicted of the early universe. It may well be a transformation repeated endlessly. But even right here, right now, amid all the wondrous phenomena of the universe, amid all the myriad persons, beings, and their lives and experience, this absolute oneness is the characteristic of existence. It is a oneness that nevertheless maintains multiplicity or plurality and differentiation. Everything remains as multifarious and diverse as before recognition of this oneness.
Nor is it a simple harmony, because it must include relative disharmony as well as relative harmony. The unifying characteristic of existence is that absolutely everything without exception is embraced on a field where each thing is really inseparable from and depends on each other thing, and where all things share the identity of emerging and disappearing from and as the formless and all-transforming, creative or generative ontological tissue of reality. The many phenomena are immanent in this one reality, this one reality is immanent as the many phenomena.
Nothing is lost in the recognition of this oneness (nothing that is, except illusion and all the suffering that arises from illusion). It is a stilling of the painful clamour of confusion and belief in the enormous conflicts of apparent individual selves, born of confusion.
The self-negation that is talked about doesn’t necessarily entail the annihilation of what we are used to thinking of as ‘our selves’. It recognises these as functional and simply part of conditioned existence. What it does point to however is that these ‘selves’ are not the true nature of identity; they’re objectifications and projections of what lies as our real self. The latter is that ground which can never be a true object, either for ourselves or others, but which is itself the true subjectivity of not only ourselves, but of others, and of all the world of relative subjects and objects. That ontological ground, (if it can even be called a ground since no relative terms are really appropriate; it simply is) is the absolute oneness of reality referred to in non-dualism.
Again, that is just my understanding of the matter!