Origin of the concept of «Oneness» in (Zen-) Buddhism

Gautama Buddha did not teach "oneness" ("ekatta") as the goal of his teachings or path. The sutta MN 1 clearly distinguishes between "oneness" ("ekatta") and the Buddha's goal of Nibbana.

Similarly, the sutta MN 121 rejects the various delusions of "oneness" ("ekatta") born of various samadhi states as being the supreme emptiness (sunnata) or Nibbana.

"Oneness" is found in Taoism, which would have probably influenced Chinese Buddhism, which is the source of Zen. For example:

Primal Virtue is deep and far. It leads all things back toward the great oneness.

Tao Te Ching 65

The Way is perfect like great space, Without lack, without excess. Because of grasping and rejecting, You cannot attain it. Do not pursue conditioned existence; Do not abide in acceptance of emptiness. In oneness and equality, Confusion vanishes of itself. Stop activity and return to stillness, And that stillness will be even more active. Merely stagnating in duality, How can you recognize oneness?

The Hsin Hsin Ming Verses on the Faith Mind by Chien-chih Seng-ts'an Third Zen Patriarch [606AD]

"Oneness" or "Advaita" is also found in Hinduism, which would have influenced the Mahayana.

As for Christian, Jewish Kabbala, Alewite and Sufi Mysticism, these are the practices and doctrines of heretics.

Jewish Kabbala probably has its roots in the Old Testament, particularity in the later teachings such as the nihilistic Ecclesiastes, which appears to normalize evil, such as in Chapter 3.

Sufism was probably Buddhism in disguise, since Buddhism did appear to continue to exist in Persia & Afghanistan for around 300 to 500 years after the rise of Islam; until the Turks & then the Mongols took control of Islam in Persia.

Syrian President Hafez al-Assad in the 1960s ordered a fatwa issued to declare Alawite as legitimate Islam because, previously, it was generally not considered to be true Islam. Since the Alawite believe in the Trinity and other aspects of Christianity, they are obviously heretics.

In summary, "Oneness" is evil Satanism because it negates 'good' & 'evil'. 'Oneness' is 'nihilism'. Gautama Buddha would never teach such evil & madness.

For example, when Muslims experience a terrible misfortune done by the evil violence of others, they declare: "It is the will of Allah". The Buddha utterly opposed this type of thinking in AN 3.61.

Also, Buddhists have often rejected monotheism, including in the Theravada scriptures (somewhere). This rejection is based on the logical argument that if there is one god, this god creates both good & evil. If this one god creates evil, it, itself, must be evil.

Case 15 of the Blue Cliff Record Preaching on Not-Oneness

A monk asked Ummon, “What is it when no thought is stirring and nothing presents itself?”

Unman said, “No preaching on Oneness.”

What makes you think that Zen preaches oneness? There are no practices that create or engender oneness. There is only emptiness and insight. Sometimes emptiness show us oneness, but sometimes it reveals two-ness. Sometimes we have to face down twoness to see oneness. The opposite is also true. You’re better off finding the place where oneness and two-ness are of single essence. Anything less is attachment to oneness. Anything more and you are lost in multiplicity.

Oneness is dead air. Twoness is a storm. Zen is both without compromising either.

Personally-speaking, I found the term on an older version of Ram Dass' website a few years ago. I don't think it was from his own words though. Also that website and him don't tout Buddhism, despite that he described solo retreats by himself, facing his internal self and attachments in numerous situations, and found a spiritual teacher to follow, things very much done in a variety of Buddhist practices. I believe on that website it originated from some Hindu teachings. This matches what other users described as a Vedic concept.

I found it a useful concept, personally. I also draw upon my Catholic background, Tao concepts as well.

To me it was a reshaping of my understanding of God. This is also not Buddhist. Buddhism does not describe the indescribable really, finds this foolish, innacurate, likely to be detrimental.

I know very little history, but perhaps I gave you another place to look if tracing it.

Oneness of the Universe was the original thesis of the (Kuru-Pancala) Vedic Religion (Brahmanism, as opposed to the later religion, the multi-deity Hinduism) - centuries before Buddhism appeared on scene. But it was never fully understood and the actual practitioners were rather corrupted, showing all kinds of real-life behaviors that went contrary to their own ideal.

Buddha had effectively cleaned it up and re-interpreted from the perspective of his own experience-centric framework.

Basically, Buddha said, the All of our lives can be summarized to our sensory and mental experience. Since experience is All, having painful and conflicted experience is the essence of suffering while having peaceful and harmonious experience is the essence of happiness.

The highest happiness or bliss, is Nirvana, the complete cessation of all limits, divisions, and conflicts that would have induced suffering. This cessation of limits includes (among other things) complete and utter cessation of any and all I-making or self-identification. So once the individual mind stops identifying anything as "self", not even the universe, the true realization of that which the concept of oneness meant to represent is achieved.

Note how this is different from the Vedic experience of All Universe as Self. In Buddha's own words, that could be liked to a dog claiming freedom from the pole it was tied to, while still running around that pole a leash-length away.

In Buddhism the authenticity of the attainment is verified in practice as absence of any longing, grasping, attachment, identification, juxtaposing, and reification. Any kind of conflicted unsatisfied mind betrays still having some limits. The liberated mind has no limits, no position, no identity, no fixed form. It is beyond even the concept of oneness and off to the Unbounded - which is what the notion of oneness meant to mean anyway. This emphasis on direct experience and personal behavior that must be in line with the transcendental realization is the trademark of the Buddha's method.

The essence of this teaching was carried along the trade routes from the original birthplace of Buddhism to Kashmir and from there to China, where it grew into Ch'an Buddhism, and then to Japan where it got known as Zen. The essential practice of Zen is direct non-verbal transmission of the first-hand experience of this formlessness and limitlessness, beyond scripture and conceptual interpretation.

Part of Chan's inspiration for making the emphasis on harmony with the natural environment comes from the ancient Chinese tradition of Taoism which teaches a similar end-state but without tying it to the social, ethical, and psychological implications the way Buddha did.

Coming back to the original Buddha's teaching, the suttas often describe Buddhist path as progression of steps taking the student from confusion to the experience of oneness and beyond. For example in MN137:

"There is equanimity coming from multiplicity, dependent on multiplicity; and there is equanimity coming from singleness, dependent on singleness.

"And what is equanimity coming from multiplicity, dependent on multiplicity? There is equanimity with regard to forms, equanimity with regard to sounds...smells...tastes...tactile sensations [& ideas: this word appears in one of the recensions]. This is equanimity coming from multiplicity, dependent on multiplicity.

"And what is equanimity coming from singleness, dependent on singleness? There is equanimity dependent on the dimension of the infinitude of space, equanimity dependent on the dimension of the infinitude of consciousness... dependent on the dimension of nothingness... dependent on the dimension of neither perception nor non-perception. This is equanimity coming from singleness, dependent on singleness.

"By depending & relying on equanimity coming from singleness, dependent on singleness, abandon & transcend equanimity coming from multiplicity, dependent on multiplicity.

"By depending & relying on non-fashioning, abandon & transcend the equanimity coming from singleness, dependent on singleness. Such is its abandoning, such its transcending."

In other words, the Buddha repurposed naive oneness of Brahmins as a stepping stone to "emptiness" - the true state of shapelessness and limitlessness which is the end of suffering.

Just like the Buddhist social ethics of non-violence, truthfulness, non-intoxication etc. lead away from the objective causes of suffering, Buddhist practice of oneness (Brahmaviharas, Formless Jhanas) leads away from the subjective causes of suffering, and all this is culminated by the teaching and practice of transcending the limits of conceptual mind - Emptiness - which removes the very ground the suffering stood on.