"We live in a world of parallels". Bad exists only if good also does.
There's dark if there's light. Male and female.
In and out, upper world and lower world (as we know or perceive them).
In simplicity, everything has an opposite.
And what about all the Thigns in the world? What's their parallel.
Their parallel is the nonexistent. The parallel in the world is what exists vs. what doesn't. Two opposites.
Either something exists or it doesn't. It's a fact. That's a parallel.
I imagine there can be, in a different universe and dimension, a situation in which we don't have the two extremes of "existence" and "non existence". Where there isn't "big" and "small", "right" and "wrong". Confusing.
In our world, as we know it, there are two sides to every coin.
And maybe our inner soul can be paralleled to our outer, visual world.