A question about the reality of duality arose at a seminar that Douglas and Catherine Harding gave recently,  and I felt Douglas came up with a very good reply: it rang true. What I heard him say was that there is real otherness in this universe. And that this must be so or else this universe would not be compatible with the existence of real love. Why? Because self love is essentially trivial. A baby sucking its own thumb. Self love may be very sweet and compelling but it is essentially immature. It would not be possible for the self love of a baby to grow into real love if the universe was all just self.
One of the exercises that Douglas suggests is looking up on a starry night, arms spread wide. I think it is very hard to do this exercise without picking up some sense of the majesty of this universe. But if the universe is all just self, then it must lack majesty and could be dismissed as just a dream. A majestic dream perhaps, but still just a dream. A.