I was sitting once when I had a sudden sense that I was the breath. Several sits later, that experience remained. An image that came to mind was of two fields separated by a wire fence; one the field of thought, and one the field of being. From each field it is possible to see into the other, but in my sit I had shifted vantage point to the field of being.
Why is breath so important? Try doing without it – it is at the apex of Maslow’s hierarchy of needs! And in setting, we focus on the abdomen, the source of energy (in the literal food sense) that is common to most or all animals. To be in touch with this is to approach the nature of life itself.
But there is another way to look at breath, and that is semantically. We inspire, we expire; it’s called respiration, and the word spirit has the same root. Just think: the early Christians had this same experience. Of course they interpreted the experience differently as a separate being, but surely the experiential roots must be the same.