The idea that everything is All One - and that meditation reveals that underlying reality is this one - and is timeless, nameless, stillness, peace... and entails a loss of self-awareness and indeed all thinking and consciousness...
This is an occult attack directed-against God, creation and all of life - against all Beings, including Jesus Christ, all Men, and all hope of resurrection to Heaven.
This, because oneness is another word for primordial chaos, the chaos of purposeless-meaninglessness before divine creation, before any-thing.
To desire oneness is therefore to desire nothing: to desire that God, creation, purpose, meaning and all that is beautiful true or virtuous... be rendered to nothing.
To seek oneness is to seek that which is as low as may be conceived; and yet to call this the highest wisdom!
Such inversion of real-values is the hallmark of Satan.