When we, as ordinary people, look around us, we see only the illusory, ever-changing phenomena, not the truth of these phenomena. It is like looking at a stormy sea. We tend to see waves and surf. We forget the truth. What is the truth? The truth is that the waves and surf are water.
We see that the universe is ever changing, and the changing never stops for a second. Buddhism calls this “instantaneous arising and ceasing.” When the tide rises, it is “arising”; when the tide ebbs, it is “ceasing.” We usually see only the constantly changing phenomena, but we do not see the noumenon that manifests these changing phenomena.
Although all phenomena arise and cease instantaneously, and are constantly changing, the noumenon of the universe that manifests and makes changes possible does not change at all. It has the qualities of neither arising nor ceasing, neither coming nor going, neither eternal nor impermanent, and neither one nor many. These are the qualities used to describe the noumenon of the universe. It is our “original face before birth.”
The terms suchness, the absolute, self-nature, the true mind, and the fundamental substance all refer to this noumenon as well. Why did the Buddha use so many terms to refer to the same thing? Because he wanted us to not be attached to any term. All these terms are expediencies to help us understand the truth. We only need to know what they refer to and should not be attached to the terminology.
~ Based on Ven. Master Chin Kung's 2003 lecture series on the Amitabha Sutra