Of course any unarmed combat technique is first of all invented for self-defense, and can also serve to strengthen the body.
彼微動，己先動」，與孫子兵法中「後發而先至」的道理相同。太極拳的高明處，就在於「化勁」﹘﹘閃避對方的拳勢，等來拳落空，勁力已終，又尚未出下一招的當兒，趁機抓準對方身體的重心點或要害，不必用很大的力量，便可制敵。