The opposites of yin and yang are the forces of female and male principles which manifest Cosmically as receptivity, and initiative respectively. These forces are united metaphysically in what is termed in Neo-Confucianism as T'ai Chi, or the Great Ultimate. In Toaism it is called the Tao that can be named.
In the Judeo-Christian Scriptures the harmony of opposites is also taught. This is seen in the famous text from Ecclesiastes, theres a time for war, and a time for peace...
Also in the New Testament, Christ is spoken of thus, Christ, the power of God, and the wisdom of God 1Cor
This is a very important doctrine to consider as Christians. We may learn a new perspective concerning God's relationship with the Cosmos, which Christians are often accused of not appreciating.
That relationship begins deep in the Godhead, as He is in His Essence. The Essence would be the Tao that cannot be named, and that Tao which can be would be the Godhead as revealed in the Beginning. The Father is that which may first be known in the Revelation of the Logos (the Preincarnate Christ), as He reveals deity. This is the First Emanation. It is in this that T'ai Chi, the Great Ultimate is known. T'ai Chi represents the harmony of Yin and Yang, the female and male principles respectively.
The Second Emanation is that of the Son, born of the Father for eternity. It is here where Yin and Yang are revealed through Li, Principle, the inner law of all things. It is also here that the Logos contains within Himself the male-female principle of Yin and Yang, refered to as Dunamis-power (Yang), and Sophia-wisdom (Yin).
It is from the dynamics of the two pole opposites as found within the Logos, from which all male-female relationships, or opposites within the Cosmos may be rooted. All change, and dyamics spring from these pole opposites within Him. Thus, the harmony is the balance between these two principles of Male and Female.