本研究從一個簡單的同音異字開始發想提問：什麼是「勢」與「式」的差別？而「勢」與「式」的差別又將如何引導我們重新思索太極拳的哲學？觀察太極拳形氣勢化的轉變過程，經論述爬梳企欲啟動有關太極拳「拳勢」的新思維。首先，從「勢」與「式」的系譜切入，經「氣論」、「勢論」和「力動」學說，探討形體與氣勢的變動流轉，「勢」一般以一定的「形」為基礎（有形則有勢；勢必因形而立），透過不可見內勢力量的蓄蘊與萌動，使之成為可見的動態形式。「勢」、「形勢」、「招勢」這些都是時間性的事件，它們雖然也都有外形姿勢，但其姿勢內裡蘊涵著指向「具體時延」的動態能量流動，是「潛在狀態」與「實在狀態」之間的流變；而「式」、「形式」、「招式」這些都是空間性的事物，這些都可以看作是無活性的「過去」存在，屬於再現體系的事物，作為法則，提供典範，成為「教」與「學」的模擬再製之用。太極拳強調的是「勢勢相承」架勢串連的套路，所有「靜止」中都蓄蘊著隱而未發的動勢，每一個「靜止」的架勢都是前一個動作的承接與後一個動作的開啟，太極拳的「勢」是動態的「形勢」而非靜態的「形式」，太極拳的「拳勢」不再只是「架式」，不再只是動作的規格、路線、身段、步態、串連與手眼心氣的配合演出，而是「氣以成勢，勢以御氣」的內在潛能動勢。

This research is inspired by a pair of Chinese homophones "propensity" (勢) and "form" (式), pronounced as shi. What is the difference between them? How does this difference lead us to reconsider the exercise philosophy of tai ji quan? By observing the constant transformation of propensity and form ("qi facilitates propensity; propensity drives qi"), this paper aims at initiating new thinking on the issue of tai ji "quan shi." The paper will start with a genealogical approach to the transformation of body form and qi shi by mapping out various theories of qi, shi, and force. "Propensity" is usually based upon a certain "form": form comes with propensity, which is established upon form. Through the accumulation of invisible inner forces, "propensity" could be visually externalized as outer "form." "Propensity" is mainly defined in temporal terms, as an event that points to the "concrete duration" of dynamic energy flow and a transformation between the potentiality and the reality. "Form" is mainly defined in spatial terms, as a representation of the inactive past and a pedagogical paradigm for the mimetic reproduction of body movements. Tai ji quan underscores an incessant cycle of "ongoing propensity" in which all seemingly static forms are loaded with surging forces and every seemingly static pose serves as the envelopment of the previous one and simultaneously the development of the next one. Therefore, "shi" in tai ji quan should be better understood as a dynamic "propensity" than a static "form." Tai ji quan shi will thus no longer be regarded merely as a set of poses with its prescribed measures, routes, gestures, steps, connections, and the integration of senses and mind; rather, it is a dynamic flow of qi as forces released from the principle that "qi facilitates propensity; propensity drives qi."