heirarchy - I don't know and don't think I am qualified to try and define it. But there is a natural order to things. I was throwing some thoughts out there that I have been recently thinking about...hoping more light could be shed on these topics...yes I feel all 4 are essential...air is really intriguing - the unknown...the inifinity of time and space...the elements essential to life in gas and plasma form. Where does air/plasma begin and end...in the earth's atmosphere or in the cosmos?