Oneness is a spiritual term referring to the 'experience' of the absence of egoic identity boundaries, and, according to some traditions, the realization of the awareness of the absolute interconnectedness of all matter and thought in space-time, or one's ultimate identity with God (see Tat Tvam Asi). Its meaning may be synonymous to that of nonduality, though some claim that non-duality implies 'not one' and 'not two', i.e. non-duality is analogous to the Hindu formula of negation and to Neti Neti, used in describing the absolute.

Oneness may also be known as Cosmic Consciousness; this term was popularized in a book by the same name by Richard M. Bucke. A functional psychological explanation has also been proposed as follows: the unification of consciousness with the subconsciousness to yield a supraconsciousness. Though some maintain that oneness necessarily transcends all consciousness per se.

Some feel that the human experiencing of Oneness expresses itself in the unity of thought and reality. They describe an experience of thought creating reality which feels like Omnipotence. However as the consciousness grows to encompass all, the ego becomes relatively insignificant. In its culmination, the seeker passes through ego death. This coincides with several teachings of different cultures:

Hinduism speaks of the Dance of Kali on the dead body of Shiva.
Jesus says: to enter the Kingdom of Heaven one has to be reborn in the Water and Spirit (see also Ergot and John 3:5 [1])
For others, Oneness, the characteristic of being one, is a term used to characterize God in contrast to Catholics who believe that the godhead is of a triune nature comprised of 3 distinct, but not separate, identities (see Trinity).

Alternatively, Oneness is the metaphysical claim of monism — that the multiplicity of beings is only apparent and that at some deeper metaphysical level all beings are really one entity or being.
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