One of these is essential to the way the physical realm works, the other is nothing more than a two-dimensional belief system. Some people use the terms duality and polarity interchangeably, but I’m going to make a strong distinction between the two for the sake of clarity.
The first thing to understand about duality is that it divides, it’s either one thing or the other. Black or white, right or wrong, good or evil. It does this through judgement, separating things and creating conflict. Duality is how human beings, who have much more in common than not, are convinced to fight with and even kill each other. Duality is used to create an “us versus them” mentality.
Now polarity is something else entirely. Where duality has a positive and negative that conflict with each other, polarity has a positive and negative that attract each other. In the case of what recently happened with our Sun’s poles, they can even switch places. Polarity is complimentary forces that work together to create balance, duality is the belief in opposing forces that conflict with each other and create chaos.
In duality one is “better” or “above” another, and this is responsible for so much suffering on the Planet. Some people believe they’re more worthy, more deserving than others, and they take far more than they need. People compare themselves to others, and judge themselves as being “better” or “worse”, which leads to an inflated ego or hating oneself. If you really want peace in your life, I recommend letting go of duality altogether.
Where duality divides things into black or white, polarity includes the full spectrum, it’s all inclusive. Duality takes the spectrum and draws a line somewhere, cutting it in half. Duality really only exists in the mind, it doesn’t directly relate to the physical realm. What people call “evil” is only the product of not seeing clearly, it’s human judgement, not something inherent to the Universe itself. What is “evil” varies from culture to culture, and also between individuals. It changes over time, as people minds and opinions change.
The only darkness is that which you can’t see, what you don’t know. It’s the fear of the unknown that makes darkness menacing and “evil”. Your eyes only see a tiny fraction of the full spectrum of light, and yet all the light you cannot see you call “darkness”. This is a perfect example of why people believe in duality, it’s a product of limited perception. It’s a judgement based upon limited senses, people see only a tiny fraction of Reality and make assumptions about the whole thing.
Understanding vibration is key to understanding polarity. Take a guitar string for instance, is a low pitch “bad” and a high pitch “good”? That’s a lot like how duality interprets things. With polarity, you go up and down the full scale to make a beautiful song, the low notes complimenting the high notes. This is a “secret” to how Creation works, not through opposing forces, but Everything coming together to create a beautiful song.