The refinement of Yi (意intention ）in horizontal fishing from Taichi Chuan
Yi ( 意 Intention/will) is the quality of the mind that directs the Chi. This happens after training the Neigong ( 內功 inner work) . The result of this training is the marrying of the Chi to the Yi , which in turn makes the Chi obedient to the Yi. Once one has learned to mobilize the Chi, then they can start to refine Their Yi. The following example uses the horizontal fishing transition from single whip. When Aaron holds my upper arm back and I try to turn with my waist and push with that arm I can barely move. The very first thing I can try is to make the mind reach with the hand that is not in contact with Aaron. Aaron is holding my left arm with both of his arms and with strength. He is making a yang energy expression. When I respond by pushing back with the arm that he is touching , then at the point of contact there is no Tai Chi. There is a double yang energy expression that can be corrected by me directing my left arm to be Yin while the active Yang energy is in the right arm. This results in Aaron and my contact point having Tai Chi . Once that is accomplished I can move again.
Another more refined method would be to activate one finger at a time starting with my pinky while the rest of the hand is passive. As I sequence through the fingers the angle of resistance is changed and this confuses Aaron making it difficult for him to find a line of resistance in which to hold the force back.
This is only one example . There is literally no end to the exploration and refinement of intention …