In Buddhism, Emptiness is the Ultimate Truth and is explained in the Heart Sutra. In the Heart Sutra, I understand that two kinds of Emptiness is described, namely Emptiness in the phenomenal world and Emptiness in the noumenal world. Usually, Buddhists explain that Emptiness means "empty of separate existence (or self)". In other words, Emptiness means that all pairs of opposites are interdependent co-arising, namely two sides of the same coin. They are not two but are not one (non-duality).
And the first half of the Heart Sutra explains Emptiness as above. Meanwhile, the latter half of the Heart Sutra explains Emptiness as the noumenal world. It is described that in Emptiness nothing (no matter) can exist and no phenomena can manifest. I understand that's because there is no space and time in the noumenal world. If so, Voidness may be more proper than Emptiness.
Therefore, there can be two kinds of Ultimate Truths to transcend the duality in the two worlds. Namely, Ultimate Truth in the phenomenal world is interdependent co-arising (non-duality), and Ultimate Truth in the noumenal world is wholeness (monism). That's why some people may make distinctions between Voidness and Emptiness. Of course, in the ultimate dimension, there is only the noumenal world, and in the historical dimension, there is only the phenomenal world.
Someone said, "One presumes, given the way the question is formed, that the "Viewer" is perceiving from the "Ultimate" State, and can still differentiate from what is phenomenal and what is Noumenal." I understand that the viewer is awareness (awakened consciousness), so s/he can transcend space and time. In other words, there is no separation between the noumenal world and the phenomenal world for awareness. Awareness can touch the true nature of reality without perceiving. This can be explained well by the theory of quantum physics called the enfolded (implicate) order and the unfolded (explicate) order. Body enfolds into consciousness. And consciousness unfolds into body.
"NOTHING EXISTS and that I AM NOT!" is a good expression of the noumenal world without space and time. Someone said, "what was being viewed around me (the universe) was no more than a concept, that objects and things are not what they are said to be". My understanding is as follows: If our mind sees psychological, physical, physiological phenomena as objects, what we see is only a projection or reflection of mind, namely an illusion or a delusion. Meanwhile, if awareness attains insight, or a direct view of truth itself without mind, what we see is the true nature of reality. (for more details: http://compassion5151.blogspot.jp/2015/11/true-nature-of-reality.html)
For Voidness (full enlightenment), we (awareness) need to throw away all notions by touching the true nature of reality. One method is mindfulness, concentration and insight. (for more details: http://compassion5151.blogspot.jp/2015/11/words-and-concepts.html)
Einstein's Theory of Relativity Photo by Elizabeth Therese Niwel