The Buddhist Philosophy as Oneness
Buddhism is a doctrine of salvation in the impermanence of every thing in this world. This impermanent world is called Samsara. There is a transcendental state called Nirvana. This form of dualism is what the Buddha tried to reconcile with Oneness in the Doctrine of Emptiness (Sunyata).
The Middle Way of Nagarjuna
Nagarjuna, founder of the Madhyamika (Middle Way) school of Mahayana Buddhism. The Middle Way is characterized by its logical refutation of any dualistic, or pluralist, view. Nagarjuna considers the concept of emptiness as a way of showing the relativity of all conventional conceptions. Even the basic elements of existence (dharmas) are taken to be void of ultimate reality.
The Mahayana sutras argued that since there is no permanent foundation beneath or within all things (conventional objects or actual modes of manifestation), the things themselves do not and indeed cannot exist. This is the doctrine of sunyata. We may associate this emptiness with Oneness.
The Doctrine of Emptiness (sunyata)
Nagarjuna considers the conventional objects, or the modes of manifestation, as the product of thought forms imposed on the Oneness, which is entirely unconditioned (not subject to limitations of any kind). These conventional objects or the modes of manifestation are that reason creates in its attempt to apprehend the nature of reality. They are purely relative and therefore ultimately unreal. The Oneness, on the other hand, is empty in the sense that it is totally devoid of artificial conceptual distinctions (without any articulation of reality).
The teaching also holds that there is an eternal, mutually sustaining dialectic between the Oneness and relative reality of the modes of manifestation or the conventional objects. Although the conventional objects or the manifestation modes are false and void in absolute terms, they are true and real in relative terms. The Mahayana goal was to transcend these opposites in ultimate enlightenment with Oneness.

