The concept is “complementary opposites”, two seemingly opposite states that “give birth” to each other. This is not exactly the “yin-yang” concept, which is more of an idea of being than one of becoming.
Sun Tzu expressed his idea of natural balance as “emptiness-fullness”. This is much closer to our modern idea of the second law of thermodynamics and entropy. Emptiness tends to fill up. Fullness tends to equal out. All things seek to level themselves. But Sun Tzu’s idea goes further: opposites will not only level but create their opposite. This difference is because Sun Tzu is not describing just natural states by the states of human interaction that are based on human psychology.
There are millions of practical applications of this idea, both in science and strategy, but the most important in Sun Tzu’s competitive systems is the fact that problems always represent opportunities. Problems are always a form of emptiness. They always represent a need for something that is lacking. If hunger is the problem, the need is for food. If poverty is the problem, the need is for money.
The mindset of look for the opportunity in a problem, rather than the lack, is the key to making progress easily. We look for “openings” in the environment, that is, a need that wants to be filling. The environment itself supports our move into that opening. Nature abhors a vacuum.
This is the secret to “winning without conflict”, which is Sun Tzu’s concept for advancing our positions without coming into expensive conflict with others. We do not move into fullness, that is, positions that others already occupy. Instead, we move into emptiness, where nature supports our move. If we are the first to establish our position on empty ground, we have the advantage of defending our position rather than attacking the position of another.
However, emptiness and fullness is only the most basic form of complementary opposites. There are a number of other such opposites that are important parts of his system. A few key ones are climate and ground, command and methods, defense and advance, spreading out and focusing, and on and on.