Over my years of research of decks and Western mythology, I saw a repeating pattern of three "lower" states of childhood and a mature state of being the prince, bride, or adult. In looking at Sufi and Buddhist spirituality, and in looking at the requirements of Celtic kings, I noticed that the fifth level, or center, was the integration of all the four states of being a healthy adult. I began to call this the four-fold way, or the four legs of the chair. The adult can sit on the three-legged stool, but the spiritual adept or royal, must have four legs.
It was obvious that these four states must be body, emotions, mind and actions (society), for that is clear in almost every fairy tale and religious practice out there. Some are only three (Indian practice) and some are five (Chinese) but most are the same sorts of divisions, even the popular fantasy, Harry Potter, where the four schools at Hogwarts are of these divisions. Of course the colors can be changed around, and some of the attributes overlap, but I have tried to make these cards with a clear distinction using color as a mnemonic.
In looking at decks that used both aspects of the cards for different meanings (upright and reversed) it was clear that this could be the basic breathing of the spirit.
The Lower Arcana was designed using the in and out movement of protection and projection in the different areas of the human being. I wanted to show that the reversed positions of the cards were not "bad" aspects but the converse of the card, or going in the opposite direction. Thus at Five, we still get the chaos or instability of the cards that you see in other decks, but we also see a kind of denial on the reverse aspect. But if you look at Ten, generally a fulfillment card or a saturation card, on the reverse, you get the healthy aspect of breathing in now ready to go to the Ace uprights with projection. The Ten uprights are "breathed out" in need of renewal and will go to the ultimate of protection seen in the Aces reversed. So everything in the Lower Arcana is movement, a snapshot of what the querent is feeling, thinking or doing.