Well I worked about the relationship of qi, ki and the christian "Holy Ghost" i.e. ruah, pneuma. ...
You can't seperate the understanding of ruah and pneuma from being the pneuma or ruah of god. Of him alone. This pneuma or ruah is send to his creation but it is not part it as ki/qi is:
Only god has ruah/pneuma. human beings / animals / trees have not. (Do we "have" ki?)
You can't direct ruah/pneuma as you can ki. You can't manage ruah/pneuma as you can ki in Shiatsu or Aikido.
You can't eat it or inhale it as you can ki.
You can't send it, as you can ki.
When God gives Adam live (Gen 2, 7) he "breathes into his nostris the breath of live" which to me is an equivalent of ki/qi the term ruah is not used in the hebrew text.
Or - am I wrong?
Ki, considered in physical terms as angular momentum, is a quantity, albeit a relative quantity because it depends entirely on choice of center, (or point of observation, equivalent to a "frame of reference"). It is the closest you come in classical mechanics to truly relativistic observations of motion and position in space. (If you follow Bishop Berkeley you can treat it as an absolute by considering all motion in relation to the "heavens of the fixed stars" but this, as he said is a convention, not a reality independent of the observer choosing it. The role of the observer cannot be dismissed, even classically, just as we see also in the perverse problems of quantum mechanics.
Kokyu is an ordering principle of that quantity. The principle of ordering divides Ki into to two apparently complementary natures, positive/negative, left/right, soft/hard, male/female, water/fire, in/yo .. etc. The binary complement understanding of the ordering is the more common conception of kokyu, but is also, as with absolute position and motion, merely a conventional ordering of a fundamental quantity. It need not have plus-minus ordering, either. It may be considered cyclical progress about the center (polar notation, for the math geeks).
Even the binary complements are also defined by a center. They move together in proper order from one predominating to the other predominating in turn. Center is not a simple geometric concept. The natural center of the male/female ordering pair, for instance, is not some dilute mixture of the two, but a child, a new being, male or female in its own right -- a new branching of the stem in Baien's conception of the unitive/divisive/creative ordering of Ki. BAien's image is of the tree as it branches -- one, becoming two, and being many -- some apparent (branches) and some hidden (roots) -- all at the same time. The center of fire/water, likewise, is steam (the pictographic basis for the image of KI, BTW) - a new thing not immediately known from the divided natures of a complementary or opposed ordering pair.
If we similarly treat the center/periphery as an ordering pair, the center may yet move during this progression of the "other" around it (relative to what, you say -- I know I know, bear with me) Then the result is not a circle but a spiral. The center moves in relation to yet again "something else" -- even cyclical progression is inherently seen also to be a "trinary" not a merely binary relationship.
Moving into the metaphysical, the temptation has been to over-read the physical relativity into a free-for-all in choices of ordering -- which is also incorrect. Kokyu, properly understood, is the "right ordering" of Ki in a given circumstance. There is a "right shape" (this is starting to sound a bit like the Noble Path, isn't it?) That order is as perceptible in any situation as it is variable and adaptable to many different circumstances in which it is found.
Consider the ordering pair of left/right. I have left eye and a right eye. Without both I cannot perceive three dimensional shape from a distance. Moreover, with both I can "see through" an obstacle to either one of them; putting a finger in front of one eye or the other, my bilocated perception allows me to see the reality the obstacle would block if I limited myself to the one eye with the impairment.
Biblically, this allows a couple of observations. The Gospel speaks of "skandalon" -- obstacles or stumbling blocks, things that block the progress of perception of the truth of reality. Christ summarizes all the Law and the prophets into the two Great Commandments of God: Love God with all your heart, mind and soul. And the second "like unto it," Love your neighbor as yourself. Self /God. Self/Neighbor. Ordering pairs again -- themselves set in an ordering pair. If you read Baien, this is a very familiar nested ordering, very much like the branching tree image he uses, very fractal in the mathematical sense of self-reflective.
The point is not to acknowledge the self as center and the "other" as peripheral, but to liberate perception by rightly ordering it -- and seeing with both centers (plural) of perception, and, ultimately, with ALL centers of perception . Let each be fully realized as a center of perception in its own right. In cooperating, in loving one another, these independent centers, like our own eyes, identify with one another; our perception is radically expanded, obstacles are defeated, and reality is seen in its true form.
"Before pointing out the mote in your brother's eye -- take the beam out of your own eye." Jesus thus directly illustrates this nature of perception and perspective. The EXACT SAME mote in my own eye seems as a beam -- whereas in my brother's eye it seems merely a mote.
The two commandments are the lessons of the Biblical text; Jesus even orders them in ultimate and proximate terms. From our perspective, the Second is the first lesson -- and a means to the First. The last shall be first and the first shall be last. First, learn to identify oneself with the "other" -- in particular. Then second, from that practical experience and training -- steadily learn to identify with the "Other" Universally.
Aikido is profound training in doing this. "Love your enemy." Liberating the centering perceptions of my whole body I learn to feel my opponent's structure and dynamic as I feel my own, and move with him as water and fire move together in creating steam. This is ki-musubi. This is kokyu-ho.