The concept of Yin & Yang is as beautiful as it is straightforward. The symbol is known all across the globe and the depth of its meaning has inspired many truth-seekers. Yet some of its aspects remain quite misunderstood. One of the biggest misconceptions is, for example, the idea that Yin & Yang would also apply to good & evil.
Needless to say, Yin & Yang symbolise the fact that there's a universal balance between all opposites: small & big, poor & rich, male & female, dark & light, decay & growth, and so on. Yet good & evil do not fit this series of dualities. To understand why, one needs to properly understand the metaphysical logic behind the symbol.
The main spiritual realisation the symbol of Yin & Yang has to offer is the idea that one should not get attached to either Yin or Yang. Since everything in existence has both Yin and Yang aspects to it, and since those aspects are always in need of each other, one should always embrace them both. The symbol thus teaches that balance in one's own life can only be found when we're able to allow both the Yin & Yang to exist, and to accept the natural flow between them.
However, there is not much sense in thinking this would imply that 'good' and 'bad' are to be embraced, just like light and dark, just like male and female, just like all things Yin or Yang. In fact, the concept of Yin & Yang leads us to quite the opposite conclusion.
In as much as we can speak of moral concepts like 'good' and 'evil' when talking about Yin and Yang, they actually only arise when someone decides to add more value to either Yin or Yang and to demote the other. 'Good' and 'evil' are called into existence when some Yin or Yang is forcefully impeded to evolve into its opposite and thus disregards the necessary balance between the two polar sides of life.
Let me give a couple of clarifying examples: It doesn't really matter whether a country is big or small, but to wage wars simply to have more land or more resources is evil. Some people become rich and some are poor, that's an economic fact, but to aggressively keep other people poor out of greed is wrong. Being male or female is, in itself, simply a difference but to assume more importance or power because of one's gender disrupts a relationship. Light and dark are inevitable opposites, but to discriminate people on the basis of their skin colour is injustice. There's a time of growth and a time of decay but to always run after profit and expansion does not only bring stress in one's own life, it also uproots the social fabric of society and the ecological balance of the world.
As such, evil or Injustice aren't a part of Yin & Yang.Rather they're a disruption of the balance and the divine flow between Yin and Yang. They aren't examples of either Yin or Yang but, in a sense, a 'threat' to the equilibrium of Yin and Yang.
All of this leads to two insights. First, it's obvious that we should indeed learn from the Yin & Yang symbol what it has taught us for centuries: Things change and people are different. We should let them change and let them be different, for that's exactly what creates the dynamics called 'life'. Balance arises when one is able to adapt to the flow of Yin & Yang. And second, those who already learned this spiritual truth should not confuse the flow of harmony and the balance of life with the dynamics of good vs. bad. Injustice is a disruption of the balance and as such it should always be countered. The symbol of Yin & Yang is therefore also a spiritual reminder that we should always try to restore the balance if it has been blocked – in our society, our relational life as well as our inner selves.
The only Yin & Yang of good & evil is that sometimes you need little effort to protect the balance and sometimes more.