Recently somebody who's been surprised by the actual experience of the internal power for the first time (thanks to my stuff *ahem*) asked basically: but what IS this energy, really?
I understand the impulse to wonder about that. That's what usually prompts other teachers to rush forward with their neat, pat explanations coming either from West (electromagnetic pseudo babble, alpha-theta electrodes, fascia fallacy - w.evah.t.f.) or East (Taoist water wheel fairies, golden light of lunar rabbit - w.evah.t.f. fairy tales). Which is why my answer to this kind of question is usually more along the lines of the original Buddha's Parable of the Arrow:
"Suppose a man was hit by a poisoned arrow and his friends and relatives found a doctor able to remove the arrow. If this man were to say, 'I will not have the arrow taken out until I know whether the person who had shot it was a priest, a prince or a merchant, his name and his family. I will not have it taken out until I know what kind of bow was used and whether the arrowhead was an ordinary one or an iron one, and how it was fletched - whether by peacock or chicken.' That man would die before all these things are ever made known to him."
I love that. Life is fleeting! There's no time for bullshit speculation. But wait - isn't the ARC concept (see my books) a "theory" of the energy? No! The ARC is an immediately tangible framework which is not a theory or reductive 'explanation' playing with words. rather, the ARC is the hands-on blueprint for your minute-by-minute on-the-floor practice sessions. The ARC is like an instruction manual for operating the B&B Precision Machine Variable Polarity Plasma Arc welding torch (NASA advanced welding torch design), not a textbook on the theory of rapid high-temperature oxidation of metallic materials.
I try to apply the Ashtanga yoga dictum '1% theory, 99% practice' over to Tai Chi and Xing Yi. However, upon being pressed, I sometimes offer the following minimal theoretical framework for the practice.
Your physical body is your ANVIL. Your mind is your HAMMER. Your etheric body (energetic endowment) is like the SWORD hammered and forged between those two by these practices to intensify, purify, sharpen and transform your energy to a higher (more fun!) state.
That's all that needs to be said and all that can be honestly said on the "what is it" question at this time. Anything more theoretical or fancy-pants than that, whether blowing at you from East or West, is likely to be bullshit and filler.
But those images above are somewhat useful, as a background thing. It's funny that after my first book Juice came out, I saw feedback on various fora etc. from experienced Tai Chi and internal arts people that Juice was interesting but too much hyperbole. Ahahaha! So funny to me. Then I was stupid, I actually toned down my descriptions of the energy in later books, so as not to shock those cognoscenti overly much. What a joke. If anything the descriptions of the energy in Juice are way too mild, not wild at all. I could have put it much more strongly and straightly, But I didn't want to shock. Turns out it was still too radical even at half-strength.
Listen up, this power is for real. It's way more even than I've described it. The problem is that the practice works along a hypexponential curve:
Dig if you will the picture: the left side of the x-axis is negative numbers. This represents the very gradual decreasing tension in your body. For most people this is incredibly difficult for reasons that are entirely beyond me, but I see this tremendous barrier and blockage by tension of all kinds in EVERYBODY I meet. Doesn't matter if it is a one-day beginner or a 20-years teacher. Everybody without exception is tense as hell. (The only difference is that the 1-day guy will gracefully accept the diagnosis and start working on it, while the 20-year guy will get all irritated and start talking about how it isn't tension or tension is necessary or what would you if I got you in a rear naked choke - anything to change the subject. So, yeah. That's what those (hopefully decreasing) negative numbers on the left of x = 0 represent. But notice it's all still just pre-flight stuff. The y-axis, representing energy experience, is still at rock bottom as we approach x = 0.
But eventually, when you relax relax enough, just prior to true relaxation x=0, you begin to feel some stirrings of the power. Those are real and valuable! But frankly "quantitatively" (if I may continue my numeric analogy here), those are the merest chickenshit compared to what's coming up farther to the right on the line! But it's a necessary stage.
At that point, when x = 0 is approached (due to finally learning to relax just a little bit) and when something is felt, a new danger arises. At that point, the more hard-headed types will say to themselves:
Huh! Fuck a duck... Whaddya know. This stuff is kinda real after all. Who'd a thunk it.. But hey, you couldn't punch thru a paper bag with this flimsy little hippie 'sensations' of buzz and tingle. So fuck it let's get back on the mitts...
... or back to physicalized bio-mechanical work of whatever kind, even Tai Chi has become bio-mechanized these days.
Now, that above reaction is actually fine. Just depends on your goals. If you want to amputate your Tai Chi before even turning the key in the door, that's fine. Just different training goals is all that is. But you haven't even begun to understand the practice so when it comes to internal, it's best to stfu, also known as: silence is golden.
Anyway continuing with the graph, once you have dropped all physical tension (crossed over the x=0 point) then with just the barest touch of mind - BLAST OFF. See how little 'mind' needs to be applied - once you cross the 0-point - to get the most unbefuckinglieable results and experiences? THAT zone, beyond x=1, where the mind can play on the relaxed body, is what I was beginning to write about in Juice but ... hyperbole. Can't shake the paying audience too vehemently.
But it does have those two pre-requisites which seems to be so extremely hard for people Relax your body, apply your mind lightly. That's all it is. Don't need no steekin' secret style of 300 moves or whatever. Nor do you need complex breath regimens, meditation protocols or other weirdness. Just use your physical body according to a few simple straightforward practices as a foundation for a quantum of energy (your starting etheric body) which the lens of your mind will build, intensify, sharpen and purify.
In Tai Chi terms, in line with the ARC, your entire lower body becomes super-charged like a radioactive neon beehive. This mindblowing power interfaces with your relaxed upper body through the lower waist and pelvis. Basically the muladhara area (basin of lower hips including hips, dantian, perineum and sacral areas) becomes energetically ionized and whoa! Back off!
But once I mention those 'physical' anatomized touchpoints, everybody jumps immediately to thinking of this as a physical process again. Want to go all Gray's Anatomy on me. But no, you aren't really dealing with the physical body any more at all. That's why I bring up the (somewhat traditional) idea of an etheric body made of internal non-physical energy but co-located with your physical, overlapping it so that it's difficult (for most people, impossible) to distinguish. But real Tai Chi is the thin wedge that allows you to distinguish and thereafter work explicitly with the etheric body.
In most people the etheric body is weak, brittle and almsot lifeless. Overlaid pressed between so much physical tension (from below so to speak) and bullshit mental and emotional overlays (from above) that it's pretty much hopeless to call it out to play. But Tai Chi can tempt it to life.
The waist and hips (energetic version thereof) are the interface point for the power, which when/if you can drop all upper body tension and arm-waving histrionics will surge up in a torrent through your arms and hands at the lightest/slightest feather touch of mental engagement or command. In terms of practical work, the best embodiment of this process is the Fair Lady's Hand secret method of Zheng Manqing Tai Chi. But I'm just beating my head on a wall here, enough. It's all in the books anyway.