Minh Nguyen Van,
(Once again, a series of questions, I'll answer each one at a time.)
1. From "The Principles of Effortless Power": on p. 11: "Performing any functional activity while
concentrating on [the center region] automatically increases the power, skill, and effectiveness of that
activity." On p. 13: "We must concentrate on our feet and the feeling in the feet...".
Question: How to do both at the same time? (it's even worse on p. 23: "One's attention must lie in
the center, the foot, and the earth"!)
There are many things we need to bring into our practice and development. In this case, the earth, feet,
and center are all related. Often we need to concentrate on becoming more aware of one area for a while in order to develop it, but this will always need to be connected with the other areas to which it is related. The center directs the whole body's movement but the ground is the source of the power to move the center, and this is accessed through the feet. Even if we concentrate for a time on one specific area or another, they are interconnected and so we need to understand not only one part but the whole. Beyond this, from time to time concentration on one thing or another can be more or less appropriate depending on what's needed or true.
2. Are the 2 visualizations, "ball and chain" and "water drop," to be chosen according to our feeling preference or are they to be both used?
PR: The purpose of such training is to become grounded, or to create an experience that can give us a sense of being grounded. Either visualization can be used, they each provide slightly different qualities. The goal is to feel these qualities as if they are real and present and so find a clear sense of ground. Once strong grounding is mastered, visualizations are not necessary, but for years they are very useful and should not be bypassed.
3. So, you said there is a minimum muscular strength used. I intended to ask you this question:
"How to get rid of the unconscious habit of using strength since we constantly use it in daily life?"
PR: Practice. Habits are built up over time, so getting rid of them usually follows the same procedure. Try not using so much strength in daily life. Find every opportunity to train relaxation and intrinsic strength in the most common activities (opening a door or lifting a coffee cup) and your development will be more certain and deeper.
4. Your visualizations make me ask questions. I've learned visualizations before but considered
them as a method of training, of helping to create new brain "cabling" or "auto-conditioning". But if you use them also, I wonder if this fact means:
a. you also use them as a method of training, of "auto-conditioning"; or
b. they are a way to make us conscious of a kind of reality we usually don't perceive, this reality being pre-existent; or
c. they create a new reality that did not exist before.
Which hypothesis is right? I tend to believe in the 2nd one because you said "things were there."
So it seems that you want us to be conscious of other realities and then live with them...
PR: One thing to watch out for is drawing a few conclusions and then assuming the answer lies within them. While it might be true that such visualizations draw our attention to some aspect of reality that we otherwise might miss, it is also true that we make up the visualizations and so they are not in themselves something "there." In answer to your question though, I might say all three are correct. We use some feeling-visual composed of familiar qualities placed in a new setting so as to train our feeling-attention to develop in a way it would not otherwise develop.