OK, let me jump in here... and, no, I haven't read the whole thread.
When dealing with issues brought to this forum's attention (examples: homeopathic efficacy, 9/11 conspiracies, dowsing, qi, telepathy), any given statement has three possibilities:
1) True
2) False
3) Undetermined
A cynic will compare the statement to what he believes he already knows, and either apply 1 or 2. A skeptic is willing to apply 3, but with the caveat that an undetermined statement does not allow for 1 to be conclusively applied.
Example: if a homeopath insists that a remedy diluted 1000 times has an effect on the common cold, a cynic will simply reply that the statement is false, as the available scientific evidence is overwhelmingly against this fact. A skeptic must look at the same facts and reply that, while it is impossible to know if this remedy will or won't ever or has ever in the past affected the common cold, all available evidence suggests this statement is false.
In the case of a lack of evidence, things become more complicated. If a believer in Christianity states that the biblical God exists, the cynic states that this is clearly false, based on a complete lack of any reasonable evidence. A skeptic should take the position that the Biblical God requires a resolution of many problems from the Biblical account, and that if paradox and conflict is to be resolved, any existing God cannot match the Biblical account. He must further state that the existence of any such God cannot be shown to exist or to not exist, causing this statement to match case 3.
The problem then for a pragmatic individual is that any statement which is indeterminate ceases to be useful. Such a statement can only be useful in the most vague, abstract ways. Saying that our world is a dream of another being might be interesting from some philosophical standpoint, but it's an indeterminate statement which lacks any practical value.
Let's examine the notion of qi for a moment:
Qi is very hard to define clearly to those unfamiliar with the concept. The origins of the concept revolves around the 'vital breath', and actually began around a superstition that all breath was an energy that permeated the world. Good air made one healthy, and bad air made one ill. Air is everywhere, air moves, and a lack of air causes death. Eventually, the concept evolved into an energy concept, rather than one involving air. This lead to mystical concepts and misconceptions, leading in turn to an entire system of supernatural belief that, fortunately to its practicioners, resulted in many positive benefits.
Yet if we look critically at the claims made by qi practicioners, we learn that much of what is being practiced is good health, good common sense, and self-control of natural bodily functions. We can remove notions of qi in almost every case and still come up with similar results to the physical practices of qi practicioners; those which appear to defy physics are, apparently, the results of self/mass delusion, tirickery, or selective memory.
I do not doubt that you've had experiences which cause you to believe in the power of qi, but I do doubt that you've applied critical thinking to those experiences. I say this because I've been along the same road many times, usually with magical/psychic phenomena. Since learning to apply critical thinking and observation, I've realized the many ways in which our minds can make mountains out of molehills, and how we can be caught up in perfectly ordinary physical reactions and believe them to be mystical.
Now, does qi exist?
A rigid definition of qi is wanting, unfortunately. The most rigid definition I can find is that qi is an emergent property of physical systems, related to the underlying order found in matter-energy relationships. Of course, this would cause qi to equal, to some degree, the laws of physics, rendering a need for the concept of qi to be unimportant. Other definitions of qi result similarly in either the concept being redundant, or being false (for example, that qi is the luminous ether).
However, I'll rely upon a common definition for qi as applid in martial arts: life energy. Obviously, life energy exists; any thing which is alive is undergoing constant biochemical reactions, which involves continual conversion of energy.
Now, can qi be used to, for example, protect yourself from harm?
By itself, no. If qi is just the common natural biochemical energy of the body, there's no particular way to focus that energy into a defensive field. You can, of course, prepare your body to lessen damage from an attack - classic 'roll with it' or 'bracing' techniques. You can, of course, mentally prepare yourself to not react to pain signals - even to ignore them completely. You can, of course, regulate your breathing and heart rate for a number of effects. Yes, these things require you to use life energy; but so does reading a book or walking to the store. Even sleeping requires the use of life energy. But of course, this once again renders the notion of qi to be irrelevant.
In the case of qi, the third value simply isn't applicable. Any given definition of qi either results in an outright false statement, or in a true statement, but one in which the definition of qi equals the definition of an existing known physical process or system.
It's like defining God as a daisy. Yes, in that case, God exists, but becomes irrelevant.
Now, that being said, an indeterminate statement does not always remain irrelevant; as new evidence is uncovered, a truth value can be assigned to a statement based on new evidence. But in most cases, until a truth value can be assigned, an indeterminate statement is irrelevant.
In some cases, the value of the statement comes from secondary results. For example, if I claim that precognition exists, we would have to say that the statement is indeterminate and irrelevant, since precognition has no resulting effects at the moment. The moment an alleged precog produces significant solid evidence of their abilities, without resorting to trickery, the statement shifts to becoming both true and relevant. Until then, however, the statement remains irrelevant.
Example: I claim I can dreamwalk. This ability is difficult to control and success is limited; further, there is no outward effect apparent from this ability, since interaction in the dreams of others is strongly limited. Hence, this claim is indeterminate (since no one, not even myself, can provide solid proof of the ability) and irrelevant, since such an ability has no objective observable effect.
So, perhaps the third value should simply be 'irrelevant'.
