The definition of duality, and non-duality, specifically in how we use it when speaking about spirituality or the spiritual search, is very, very simple.
Duality means more than one thing. Non-duality means not two. “Not divided” is really a better way to say it, because we often get confused and think it means there are no opposites: male and female, up and down, green and red. That’s not what it means.
It means that things are not separate.
You can see the whole forest, or you can divide it into all the different trees in the forest. Non-duality means seeing the full forest, understanding that all the trees grow within the forest.
More importantly, human beings tend to see and interpret reality as separate from us. Non-duality means that nothing is separate from me. There aren’t two of me. I don’t have a lower self and a higher self. I don’t have a good me and a bad me. All the different voices in my head are not separate selves.
And I am not separate from reality itself, from the Earth itself.
Duality, when we’re stuck in the feeling of separation, is what causes so much of our anxiety, angst, and pain, because we feel alone and separate.
In non-duality, you can’t feel alone, because you’re blended in with everything.
You can throw different words at it: duality is separation, the belief in separation, the belief in an individual self. There’s me all by myself, and there’s you all by yourself.
Non-duality says there is really no separation between you and me that we can find. Everything is intertwined.
Most important, non-duality is simply a statement about how reality itself is. It’s a statement about how life is. Everything is intertwined. That’s the reality of the universe, the reality of Earth, the reality of you and me.
Duality is an illusion because it doesn’t actually exist. We invent it as something that exists, and then we create all sorts of concepts to describe the duality we’ve invented.
So, non-duality is not a thing itself. It’s the way things are.
Duality is our imagination of how things are. It’s our illusion. It’s all the names we’ve put on everything.
The reason we say “nondual” instead of “unity” is because you can turn unity into something outside of yourself. You can think, “I’m trying to find unity. Where is it? I’ve got to find it somewhere.”
It’s easier to understand the negative statement: There is no division. There is no separation.
There is not two.