"It is because everyone under Heaven recognises beauty as beauty, that the idea of ugliness exists. And equally if everyone recognised virtue as virtue, this would merely create fresh conceptions of wickdness. For truly Being and Not-being grow out of one another; difficult and easy complete one another. Long and short test one another; high and low determine one another. The sounds of instrument and voice give harmony to one another. Front and back give sequence to one another. Therefore the Sage relies on actionless activity, carries on wordless teaching, but the myriad creatures are worked upon by him; he does not disown them. He rears them, but does not lay claim to them, controls them, but does not lean upon them, achieves his aim, but does not call attention to what he does; and for the very reason that he does call attention to what he does. He is not ejected from fruition of what he has done."
This chapter of the Dao De Jing is very profound, and talks about the interplay of Yin and Yang. Lao Zi says that a wise man should be in harmony with the cycle of change in the cosmos and the same applies to martial arts. In Tai Ji Quan we never oppose the opponents force. Instead we compliment it. We are not, however, floppy and lifeless. Yin and Yang must be in harmony, so if someones attacks, we may feel very hard to them, but that is not opposing or using muscular strength. It is using the mind, and it feels like an inflated balloon. We allow the opponent to fully extend his power and ultimately use it against him - actionless activity. In the Tai Ji Quan classic written by legendary Taoist master Zhang San Feng, he says:
"You must emphasise the use of the mind in controlling the movements, rather than the mere use of the external muscles. You should follow the Tai Ji principle of opposites: when you move upward, the mind must be aware of down; when moving forward, the mind thinks of moving back; when shifting to the left side, the mind should simultaneously notice the right side-so that if the mind is going up, it is also going down."