"Gao Fu, a Chen style master, was asked this question: What makes a T'ai-Chi movement a T'ai-Chi movement? Her reply was that if the intent leads the energy and the energy leads the muscles and bones then it's a T'ai-Chi movement. If the mind goes directly to the muscles and bones, bypassing the energetic level, then it's an ordinary movement. I like this definition because it's principle-based rather than tradition or form based. It also implies that in order to feel into the inherent balance underlying the surface of anything (T'ai-Chi means essentially unforced balance) I have to surrender to that holistic body intelligence that I call "energy". I can't force it or have it on my own terms. I don't make it happen, I allow it to emerge. I don't train to increase this balance since that is impossible. I train to increase my experience of that balance and innate intelligence, to give it more avenues through which to express itself and because it's a pleasure to participate in the movement of the universe.
This is a pretty abstract definition. Practically speaking I would also add that a good T'ai-Chi movement should be rooted in the feet and powered primarily by the legs. The waist should direct that leg generated power with some degree of turning. The power should move up the spine and gather strength between the shoulder blades and finally issue out the arms to the hands. This is easily said, but in practice many T'ai-Chi practitioners end up powering their movements with their waists or arms. If the waist powers the movement, the root usually ends up being in the pelvic floor instead of the feet. This usually results in knee problems as the legs are not grounded and end up twisting. If the movements are powered by the arms one ends up with so-called "local strength". Local strength means the arms move separately from the ripple or wave of power coming up from the feet and legs. Gao-Fu's definition is profound but general. It implies that in order to improve my experience of personal and universal balance, not to mention martial ability, I need to stop forcing the muscles and bones through the use of will power. I need to relax into the "energy" level of awareness and let the muscles and bones follow."
- Gene Burnett, Questions and Answers