My understanding is that the unconditioned dimension of my mind is the dimension that is in union with Life/Infinite Being/God, or whatever we call that Incomprehensible Mystery. I like the author's saying that the unconditioned dimension is like the fresh water in salt water. It's all me, fresh water and salt water combined, and part of growth, purification, and enlightenment is to distil the salt water to release and allow and have the fresh water, the soul, the unconditioned dimension. I think it's what John Dewey meant in saying that it is important for each of us to get ourselves in line with the moral axis of the universe. What has helped me is times when I am listening closely, paying attention, open to consider and learn. It's when I use my eyes to see and ears to hear what is and not what is my preconceived thinking. It's when I have the beginner's mind, as the Buddhists say. My sense is that I tap into the unconditioned dimension periodically and briefly, and in those moments I feel a sense of being right on which is satisfying. Then I'm back to the salt water.