(First of Forty Tenets of Plum Village)
"Space is not an unconditioned dharma. It manifests together with time, matter and consciousness."
(Space is not a separate existence. It is interdependent co-arising with time, matter and consciousness.)
(Second of Forty Tenets of Plum Village)
"In the historical dimension, every dharma is a conditioned dharma. In the ultimate dimension, every dharma is an unconditioned dharma."
(In the phenomenal world with space and time, everything or every phenomena is not a separate existence. It is interdependent co-arising with everything else. In the noumenal world without space and time, no separation is there and only the wholeness is there. So, every object of mind is unconditional.)
2) The ultimate truth in the noumenal world (ultimate dimension)
"Non-separation or wholeness" is the ultimate truth in the noumenal world. There is no duality. So, there is no need to transcend the duality in the noumenal world, or the ultimate dimension. It is also called "Emptiness", "Voidness" in other words. In the noumenal world, there is no space and time. So, nothing can exist, and there are no pairs of opposites like birth and death because of the extinction of all notions. Only nature (Buddha nature, Divine nature, Awareness) can be there. The method to attain the non-duality here is the insight of the true nature of reality (wholeness). When we understand that the wholeness can't be cut into pieces by notions, we are convinced that all notions are wrong. All notions were created by human ego for separations. So, we can easily throw away all notions and attain the non-duality. This non-duality is different from the non-duality through "interdependent co-arising" in the phenomenal world. That's because there are no notions of A and B. Only the wholeness is there. The non-duality in the noumenal world is not based on the duality. "Non-separation or wholeness" must be the only and perfect way to attain the non-duality in the noumenal world.
In the Heart Sutra, the ultimate truth in the noumenal world (ultimate dimension) is described from "是故空中 (So, in emptiness)" till the end of "般若心経 (Heart Sutra)". Especially, the ultimate dimension is clearly mentioned by "無苦集滅道" (there is no suffering, there is no making of suffering, there is no secession of suffering, there is no path leading to secession of suffering). That's the ultimate dimension (noumenal world). There is no separation, discrimination, or the duality there. So, if we (awareness) dwell in the ultimate dimension, it is impossible for us to suffer.
Now you can understand the meaning of "Suffering is impossible without separation." In the noumenal world (ultimate dimension), suffering is impossible. That's why there is no making (cause) of suffering, there is no secession (end) of suffering, there is no path (method) leading to secession of suffering.
Therefore, "Non-separation or wholeness" enables us to attain the perfect non-duality. We are all the same, as the whole cosmos. Not only humans but also all animals, plants and minerals are the same, as the whole cosmos. We can completely stop separating ourselves from others through this non-duality, or the wholeness. So, there is no space for any afflictions to arise. Therefore, we can completely liberate ourselves from sufferings.
David Bohm explained the relation between the noumenal world and the phenomenal world as follows:
"In the enfolded [or implicate] order, space and time are no longer the dominant factors determining the relationships of dependence or independence of different elements. Rather, an entirely different sort of basic connection of elements is possible, from which our ordinary notions of space and time, along with those of separately existent material particles, are abstracted as forms derived from the deeper order. These ordinary notions in fact appear in what is called the "explicate" or "unfolded" order, which is a special and distinguished form contained within the general totality of all the implicate orders."
"The implicate, or the enfolded order unfolds into the explicate order, or everything separate. (The explicate, or the unfolded order enfolds into the implicate order.)"
【The historical dimension (phenomenal world) enfolds into the ultimate dimension (noumenal world). The ultimate dimension (noumenal world) unfolds into the historical dimension (phenomenal world).】
"Now, the implicate order would help us to see that, to see everything enfolds, everybody, not merely depends on everybody, but actually everybody is everybody in a deeper sense. See, we are the earth because all our substance comes from the earth and goes back."
So, if we touch the phenomenal world deeply, we can touch the noumenal world. It is amazing that the Buddha touched the noumenal world (ultimate dimension) 2,600 years ago and understood the wholeness (ultimate truth in the ultimate dimension), just like what David Bohm explained through quantum physics.
By the way, there is one more truth called "the conventional truth" in the phenomenal world (historical dimension). This truth is familiar to most of the people in their daily life. It is based on separation, discrimination, or the duality. They see everything as follows:
"A and B are two separate entities.
So, A is not B.
That's why A is A."
This dualistic view separates oneself from others. Afflictions arise from this separation and make them suffer. So, they need to transform their suffering to happiness. Now you can understand the meaning of "Transform your suffering to happiness." And we need to remember that in the Four Noble Truths, all four truths are the conventional truths.