There are three different levels of training in the union of the two truths. One is according to Sutra practice, the second is according to Action Tantra, and the third is according to Highest Yoga Tantra.
In Sutra, Buddha explained in more detail how to understand the two truths. First he explained ultimate truth and conventional truth separately, then how to understand the union of these two truths, and then how to understand that this union of the two truths is inseparably one nature.
These are more and more subtle - deeper and deeper. Understanding emptiness itself seems quite easy. Subtle conventional truth is more difficult. The union of the two truths, which means understanding that these two truths are inseparably one nature, is more subtle, deeper.
Yesterday I told you that when we realize the union of the two truths then our understanding of emptiness is completed.
In the Heart Sutra it says:
`Emptiness is not other than form; form also is not other than emptiness.’
This clearly shows that these two truths are inseparably one nature. Yesterday I also told you that our body, for example, is conventional truth and the emptiness of our body is ultimate truth. What is the emptiness of our body? It is the mere absence of our body that we normally see.
So the emptiness of our body is ultimate truth and the body itself is conventional truth, but these two truths are inseparably one nature. There is no body other than emptiness, and there is no emptiness of the body other than body.
This is not easy unless you deeply contemplate and meditate continually, then you will gradually understand. Finally we realize that our body does not exist outside of emptiness. It is just mere name. Body is just mere name. This mere name and emptiness are the same.
We can individually study first the subject of emptiness, then conventional truth, and then the union of these two truths, which are also explained in many other books, especially in chapter three of Mahamudra Tantra, called What is Emptiness?, as well as in Transform Your Life and in many other books.
I wrote it in all these because I thought that the more books I put this explanation in, the more people could see it! This is our generosity, our Dharma gift, because if we only put it in one book, some would see this book and others would not; but if we put it in every book, whoever receives any book it will appear to them!
So this is our wisdom generosity, distributing wisdom. Directly people receive the book in their hands, but from that their wisdom will increase whenever they read it. So our real gift is wisdom. We are distributors of wisdom. Our publishers are wisdom publishers! We are benefactors of wisdom. We are destroyers of ignorance!
From our side, we are not destroying mother sentient beings. We never destroy mother sentient beings. We never get angry with mother sentient beings. If we really want to get angry, we should get angry with our delusions, our ignorance. Therefore, for these beneficial reasons, you can see this subject in every book you can see, in many books!
So, to understand what conventional truth means, what ultimate truth means, and how these two are inseparably one nature, first we should read carefully, or listen to teachings and read Dharma books. Then we should try to understand this from our own side, and experience through contemplation.
When we think that what Buddha said is the truth -- that emptiness is not other than form and form is not other than emptiness – we realize ‘my body is not other than the emptiness of my body; the emptiness of my body is not other than my body. These two are not separate. They are inseparably one nature.`
When we realize and experience this from our own side, we then we should meditate. We should hold this knowledge without forgetting and continually contemplate and meditate until we gain deep familiarity.
So, gradually we will understand that everything that exists is inside emptiness, not outside - but it is also not other than emptiness. It is in reality emptiness itself, ultimate truth itself. It is a union. `Union’ means that what was previously two now becomes one, which is ultimate truth itself.
Then in this meditation, or concentration, for us everything, all phenomena, are equal in emptiness. Therefore in the Perfection of Wisdom Sutra, Buddha said that the training in the union of the two truths is called `training in equalizing samsara and nirvana`. In the Perfection of Wisdom Sutra and also in more detail in the Ambhisamayalankara commentary, he explained training in equalizing samsara and nirvana.
It seems impossible – how can we equalize samsara and nirvana because samsara is the nature of suffering and nirvana is the opposite of samsara? How can we equalize them?
But samsara is not other than emptiness and nirvana is not other than emptiness. In emptiness they are equal. There are no such opposite things; they do not exist in emptiness. Everything - emptiness and mere name. Mere name itself also is not other than emptiness.
So in emptiness everything becomes equal, peaceful, and comfortable. It is an amazing, great experience. So in Sutra, training in the union of the two truths is called `training in equalizing samsara and nirvana.’