The answer, Kevin, is that nobody knows this, in the way they know that 3+3=6. What I will say is that every saint and teacher I have studied has said this, or some version of it. Ram Dass, Ramana Maharshi and on down the line. The book I recommend would be "Be As You Are" which is the book of Ramana Maharshi's teachings. It's short, sweet and gets to the point of our natural state within.