In terms of philosophy, the principle of yin-yang is perhaps the most well known. In terms of practice, the flowing characteristic of Taijiquan is most noticeable. As Goh withdraws his attacking arm to prepare for the next move, Sifu Wong flows with Goh's movement, following the withdrawing movement but guarding his hand to prevent Goh's counter-attack. Of the softest things in the world, Nothing is softer than water. Any hard object in the way Will be defeated by water.
Water never changes.
Hence soft defeats hard, Weak defeats strong. But few practise it. In Taoist writings, water is not just water. The first picture shows what would happen if Goh fails to respond appropriately. As Sifu Wong sinks down his stance, Goh would be injured or pushed away.