Ultimate truth is understood through relative truth, otherwise we have no basis for understanding it.
When we talk about the ultimate nature of things it has to be understood through the nature of interdependence. Everything is dependent, interdependent. There does not exist anything short or long on its own. When you think about something short, it is related to something long. If you say this is long, then there must be something shorter. Nothing short or long exists on its own. Short and long are related to others.
In some way, when you think about east we can say east, because there is a west.
When we talk about emptiness it has to be based on the understanding of related things. The reflection of the moon on the water does not exist on its own. There has to be a moon in the sky, water, reflectibility. When all these things come together then you see the reflection of the moon in the water. That is emptiness. Emptiness and interdependence go together, because everything is interdependently arising and interdependently designated. Nothing exists on its own independently, therefore the nature of things is emptiness. Because everything is empty, everything is interdependent, it means everything is possible. We think everything is fixed, just as it is, but it is not always like that.
Take poison, for instance. We think of poisonous plants as something very negative, but a lot of poisonous plants are not poisonous for some animals.
So does that poison really exist on its own? If it existed on its own it would kill every living being. As it doesn’t kill everything, we can say that nothing exists on its own as it is. It’s all interdependent, all dependently arising.
Ultimately it is emptiness. Emptiness, or ultimate truth is the understanding of relative truth. If ultimate truth is seen as something separate, not based on relative truth, then that approach is like nihilism. It’s like saying; “there is nothing there,” but it is not like that. The most wonderful thing is the togetherness, the co-emergence of ultimate and relative truth.
Things are empty in nature but they arise interdependently. Therefore, they are empty. Therefore, everything is possible. That is the most wonderful nature of things.