Yin and Yang is a pretty cool concept. It comes from Taoist metaphysics.

The Tao is made up of yin and yang elements. Tao kind of means “the way.” But, the first line of the tao te ching is “the tao that can be named is not the eternal tao.” So yeah. It’s kind of like quantum physics. If you think you understand it, you don’t understand it.

Positive and negative forces balance each other. If you look at the symbol, you’ll see little dots of white in the black and little dots of black in the white. There can be no light without dark. In fact, for light to exist, it needs darkness. It is only by defining dark can you explain light, and vice versa. Not only that, but there exists in everything that is dark, a little bit of the light. You need light in order to see the darkness.

This holds true with every binary concept like up and down, male and female (a banana is actually the ovary of the banana tree), left and right, and of course good and evil.

This means there is no such thing as pure evil. Evil literally needs good to define it, and within every bad guy, there is always a spark of good. And, or course, vice versa.

The Tao and the concept of yin and yang has permeated Chinese culture in a similar way that Christianity has permeated Western culture. Even those who don’t go to temple, still have a culture of Taoism. Much like an American might say “patience is a virtue” and not know it’s biblical origin, a Chinese person might say 三人行必有我师 (Sān rénxíng bì yǒu wǒ shī) to similar effect and not know that it comes from the writings of Confucius. The phrase literally means “(where) three people walk, (there) must be my teacher (among them)” and means you should be patient and willing to learn from anybody.