The two halves can transform into each other. So there are both external and internal contradictions and for that matter both external and internal interactions. The result of such transformation is the production of pluralism. Mutual production and mutual overcoming as the seasons rotate in cycles of rise and fall unite man and nature. All things are related.
Reality is also a process of mutual transformation.
But the essence of the reality is always the same, the will to survive. Transformation between yin and yang ensures the success of the survival and meaningful life in society. Harmony is not static. It is a result of dynamic operation. Harmony between yin and yang reinforced the Doctrine of the Golden Median.