Softness in Taiji doesn’t mean being weak or having no power. Being extremely soft is the high level of “Bu Diu Bu Ding” (neither leave the opponent nor oppose him); it is like a shadow that follows the body. When you touch your opponents (who know the real Taiji, of course), you feel like you are touching the emptiness, and you cannot feel his center. When you advance, you fall to emptiness; when you retreat, you lose your advantage. Hardness in Taiji is like when you feel your opponent’s enormous power; you have no chance or opportunity to get the upper hand. In other words, after a long period of training, it can create a waving power or “Gu Dang Jin” in your body. It is the Jin that is full of elastic power, and it can rebound your opponent’s force from any parts of your body, like the ocean wave that can support a boat with ten thousand tons.
-Yang Yuting, a Northern Wu style Taijiquan master-