I do not believe one can say that duality is essential.
There is all possibility that reality is a monism, specifically a physical one. Why I say possibility is because the evidence for a mind can only be found in its existent physical manifestation. Whether this is evidence of a mind remains an open question.
Modern scientific evidence points to consciousness as being an emergent property of the physical brain.
I will grant it is possible to think in terms of dualism (and many people do) but whether the evidence can uphold this position is another question. Far easier (and more plausible, but not necessarily true) is the material monism. Again, I feel this is true of material monism as well when compared to the ideal monist position.
Again, I do not mind the holding of such dualist or idealist positions so long as one can justify their positions with the evidence and reason at hand.