So, what is it then, this Ki ?
You say, it's a concept, which means an abstract or generalized idea.
And you say, it's a felt understanding.
Yes, Bernd, it is both!
Ki, and its equivalents, qi, prana, etc, have been mentioned in literature spanning thousands of years; so, as a concept it has been discussed extensively. It has also been the basis of health systems that are still in use.
This is not to say it has not been questioned and challenged - the Vitalism vs Atomism/Mechanism debate has raged in ancient Greece and India for centuries. However, both the Vitalism and the Atomism theories are just that - models that have some coherence and some evidence to "prove" their existence.
As W. Edwards Deming, adviser to Japan after the war, said, "All models are not true; but some are more useful than others."
Koichi Tohei taught that ki is a highly useful model for understanding aikido and performing it excellently. Not only that, he believed it is also a useful basis for self-mastery and personal transformation. Tohei was the first person to articulate Ueshiba's teaching in terms of ki, and to develop a system to learn and practise ki.
In his 1961 book Aikido: The Co-ordination of Mind and Body for Self-Defense
("Supervised by Morihei Uyeshiba"), Tohei said that ki was one of the most frequently used words in Ueshiba's dojo at the time, in expressions like ki wo neru
(to train your ki), ki wo totonoeru
(to prepare your ki), and ki wo dasu
(to pour forth ki).
It therefore comes as a surprise that, on Ueshiba's death, his son Kisshomaru and other instructors went into denial about ki, and effectively told 10th dan head instructor Tohei to pack and go. I rather suspect that, as Japan was then going through immense technological development through the adoption of Western mechanistic philosophy and methods, they dropped the "esoteric" side of aikido in order to appear progressive.
I have heard mechanistic teachers say, "Don't worry about ki, you may or may not get it - one day." Why wait? Why not develop ki now?
The best way - actually the only way - to understand ki is through felt experience. In my experience, when aikido is performed with awareness of ki, it is qualitatively different. The movements become smoother, and almost effortless. One has access to a different mode of power. For example, a petite student came up to me once to ask how to deal with a beginner, a tall largely-built man, who was holding her wrist very tightly. I asked him to hold me, and sure enough, it was tight and he was immovable. I decided to relax and use ki, and he flipped over and landed on all fours. Only experiences like these enable a person to validate the effectiveness of using ki in aikido. This is what Tohei calls mind-body coordination. Ki is the interface between mind and body, and is the vehicle to integrate them such that the result is greater than the sum of the parts.
On the side of the uke, when I was thrown by my teacher, I never felt any strength or resistance. Therefore there was nothing to resist. I just felt my attack being absorbed, dissipated or diverted, I moved comfortably and willingly, and only realised the power of the throw when I landed on the mat.
Developing sensitivity through the awareness of ki is crucial for instant response to an attack. We are taught to extend ki when facing an attacker - in fact at all times in one's daily life. Then one can detect the opponent's ki - their intention to attack - even before they have physically started the attacking movement. If one has a mechanistic approach to aikido, "If one reacts only after he sees his opponent's hand or feet move, he will be too late." (Maruyama, Aikido with Ki, 1984)
Thus, Ueshiba said,
"Seeing me before him,
The enemy attacks.
But by that time
I am already standing
Safely behind him."
My contention is that aikido was meant by its founder to be a means of personal transformation and individuation. This means that a holistic approach is needed: one that integrates body, mind and subtle energy - ki. It involves opening oneself up to a way of thinking, feeling and practising that is sometimes vague, sometimes seemingly beyond reach, yet sometimes very clear and tangible. Ki is not easy to grasp, it takes time, and it needs a sense of letting go rather than intellectual analysis. To have a mechanistic, reductionist approach to aikido reduces it to physical techniques and nothing else. That is why many people misunderstand aikido in relation to "self-defence," and why there is so much confusion about the purpose and modern-day relevance of aikido.