Truth
But here is a very , very important point: in itself, truth has no function. Zen died out in China because many masters attached to words like these and could not perceive how this view of truth must function, from moment to moment, to help other beings. Zen lost its bodhisattva function and became a word game for the elite. Many Zen masters still say, "Yah, mountain is mountain, water is water. That is truth." And they are right: this is truth. But if you stop here, this is still an abstract view. It can remain a purely metaphysical truth. One more step is necessary: What is the correct function of truth? How does this truth connect with you and all other beings? How does this truth function in your life?