According to Osho, duality is a mental construction: the mind is 'the other.' When you realize total aloneness, mind ceases, and with it both separation and the compensatory idea of oneness. Reality is conceptless, not-two (advaita); philosophy invents opposites, while true religion dissolves the inner barrier so existence is simply itself, indivisible.
Your thinking creates the feeling of ‘me versus other’; when thinking stops, there’s just one seamless being.