This is a very fundamental concept of Eastern Philosophy and is most basic to the thought process of Taoism.The implication of this term is discussed in detail in the classic books of Tao Te Ching and I Ching. The symbol of this concept is very popular nowadays though not all who wear it on the top of their t-shirts or even hang it on signboards outside their Martial Arts Schools know the underlying meaning of this.

In simple terms the meaning of this symbol is that in everything positive is something negative and in everything negative there is something positive.Mind you, by positive and negative here no reference is being made of good and bad. The positive and negative are the attributes which complement each other-- pairs of opposites like the day and night, light and dark, hardness and softness or the masculine and the feminine. These pairs of opposites are essential for one another and both are necessary phenomenon.For Western Thought on this subject go here
So hardness and softness are equally essential.And this fits for every aspect of life.
Likewise, in the world of martial arts hardness and softness complement each other.There are styles which go by the sobriquet "Hard Style" and there are others which call themselves "Soft Styles".Neither is a better style than the other.Neither is a worse style than the other.The best Martial Artist is the one who can fit both the hard and soft into his approach.The best martial artist has to be soft enogh to counter the hardest of attacks with the
minimum effort, while he has to be hard enough to be able to vanquish the toughest opponent.It has been said about one of the best fighters of the century
,who had little known connection with the martial arts that we are talking about that He floats like a butterfly and stings like a bee
This shows the necessity of merging hardness with softness. The true Martial artist has to merge:



After strainuous thought the answer came to him while on a boat , floating in the sea. Just like the calm waters of tjhe sea reflect the clouds without a ripple, our minds should be calm enough to register the combination of movement of the opponent without being disturbed by it. We must think while in motion , but at the same time be absolutely calm. That comes from viewing Martial Arts as meditation in action.