It gives divine joy to the mind, when one realizes the spirit of oneness. Even in Bhagavad Gita, when Arjuna questions about true knowledge, the supreme Lord tells him that true knowledge is identifying oneness in all the matter and energy around us. However, if actually oneness were the only truth, then why will it require the reference "oneness? What is meant, is that, when we refer to oneness, we are actually implicitly acknowledging the existence of duplicity. The true "oneness" must be so unique, that it should be free of all references. However, at the same time, we cannot perceive anything without reference. So is our understanding of oneness paradoxical?
Are you talking about unity or non-duality?
It's possible to be a non-dualist without asserting unity. It isn't that you're rejecting unity, it's just that you reject duality and make no (positive) assertions in its place.
Likewise, it's possible to assert unity while implicitly asserting duality. The problem here is that to even assert something is to imply the existence of its opposite, otherwise why assert? Why do we need to speak (or think) X if there is no not-X?
Can you see the problem? This is fitting, as the non-dualist points to conceptualization as the problem. Not a specific concept, but conceptualization. Well, if you try to fix conceptualization with conceptualization, are you really fixing anything?
In fact, I read this as the fundamental difference between Buddhism and Hinduism. Hinduism asserts unity. Buddhism asserts non-duality without asserting anything else. Yet this is a hard position to maintain, so a variety of positive assertions were made, yet these were a mistake, so a variety of attempts to counter those assertions were made, and the result is much of the (apparent) nonsense, contradictions, logical flouting and... well Nagarjuna :)
Yet if we look at Buddhism and Hinduism as being non-dual, we can see them as choosing two paths to solving the same problem.
The key here is realization; one is supposed to realize non-dualism, to feel or perceive this, perhaps even as a realization of how baseless duality is. One should not reason about this, or if one does so, to do so only insofar as is needed to get one on the right track (or just off the wrong one).
If you haven't done so, I recommend you read David Loy's Nonduality. It's a solid treatment of this subject.
Here is a speculative solution to the paradox:
There is "oneness in all the matter and energy around us", but consciousness is an exception to that oneness; you can observe this if you realize that there is no apparent continuum between your consciousness and another's; therefore consciousness is like a singularity point in the oneness which surrounds it.
Now, by consciousness I refer to the so called qualia, or to what is possibly referred to as watching in some eastern philosophies; it doesn't include ones psychology and cognition, which relative to watching are part of the "external" oneness and the continuum.
to make a metaphor, think of the galaxies in our universe, where each galaxy consists of hundreds of millions of stars orbiting a central massive black hole, which is a singularity in spacetime; these galaxies are part of an ever changing continuum, and yet each black hole is a separate singularity; a person is such a galaxy, and in its center there exists a singularity we call consciousness or watching.
Now, not only is that singularity separate, it also does not seem to change; this is because we can ascribe to it no attributes, and therefore we cannot say it ever changes; so watching is both separate and constant.
This seems to be in conflict with Buddhism, which I believe preaches that everything is in constant change, and nothing is separate; therefore, it seems as if Buddhism rejects the existence of watching, just as so many contemporary philosophers and scientists reject the existence of qualia (e.g. Dennet, and most physicists); could this view of Buddhism be the influence of a single philosopher such as Nagarjuna?
I am aware that this is all free-styling speculative, but I have not stumbled on similar ideas or discussion elsewhere, and I welcome corrections and comments.
Referencing oneness does not establish a duality if the agent of awareness (in this case the self) is a subset of the One.
As you observe, we can see that the One would have nothing outside itself for reference. The One itself is incongruous with categories or divisions of any kind.
However, a point of self-consciousness that exists in the context of time, place and other references, is bound to relate to them, in fact is defined by them. One of these references can be the relationship of the self to that which is beyond reference.
The neo-Platonist philosopher Plotinus identified a continuum of relationship from the individual item to the perfect unity of the One. His view was that we as individuals find bliss and fulfillment insofar as we approach "likeness" to the One, as opposed to the veil of tears he called "differentiation," fraught as it is with ambition, competition, desire. I believe this is a similar construct to that of Buddhism, but I defer to those with expertise on the subject.
I know I have heard consistent advice from esoteric teachers that we should eschew our individuality, try to blend back into the All or the One through various techniques, including meditation, and various life choices, such as asceticism.
However, given our natures, and assuming that we take our present form only for a time and in a particular place, it appears our differentiated selves are the only window we have on the One, which is our source, and in some way our home. So, I must account such awareness as precious, even if its existence only reinforces how temporary and fungible are all subset constructs in contrast to the great construct that includes everything. So identifying the concept of "oneness" strikes me as entirely worthwhile, in that it helps us understand ourselves.