The four seals mentioned above have profound implications for a Buddhist practitioner. The first seal states that all compounded phenomena are impermanent. The question of impermanence has been expounded most fully by the Sutra Follower (Sautrantika) school, which explains that all compounded phenomena are by nature impermanent, in the sense that due to its being produced from a cause a phenomenon is by nature impermanent or disintegrating. If something is produced from a cause, no secondary cause is required for it to disintegrate. The moment that it was produced from the cause, the process of disintegration has already begun. Therefore, its disintegration requires no further cause. This is the subtle meaning of impermanence that anything produced by causes is 'other-powered' in the sense that it depends upon causes and conditions and therefore is subject to change and disintegration.
This is very close to the physicists’ explanation of nature, the momentariness of phenomena.
The second seal states that all contaminated phenomena are of the nature of suffering. Here, contaminated phenomena refer to the type of phenomena which are produced by contaminated actions and disturbing emotions. As explained above, something that is produced is 'other-powered' in the sense that it is dependent on causes. In this case causes refer to our ignorance and disturbing emotions. Contaminated actions and igno-rance constitute a negative phenomenon, a misconception of reality, and as long as something is under such a negative influence, it will be of the nature of suffering. Here, suffering does not only imply overt physical suffering, but can also be understood as of the nature of dissatisfaction.
By contemplating these two seals concerning the impermanent and suffering nature of contaminated phenomena, we will be able to develop a genuine sense of renunciation, the determination to be free from suffering. The question then arises, is it possible for us ever to obtain such a state of freedom? This is where the third seal, that all phenomena are empty and selfless, comes in.
Our experience of suffering comes about due to causes and conditions, which are contaminated actions and the ignorance which induced them. This ignorance is a mis-conception. It has no valid support and, because it apprehends phenomena in a manner contrary to the way they really are, it is distorted, erroneous and contradicts reality. Now, if we can clear away this misconception, the cessation (of suffering) becomes possible. If we penetrate the nature of reality, it is also possible to achieve that cessation within our minds and as the fourth seal states, such a cessation or liberation is true peace.
When we take into account the different explanations of various philosophical schools within Buddhism, including the great vehicle schools, it is necessary to discriminate those sutras that are definitive and those requiring further interpretation. If we were to make these distinctions on the basis of scriptural texts alone, we would have to verify the scripture we used for determining whether something was interpretable or definitive against another sutra, and because this would continue in an infinite regression it would not be a very reliable method. Therefore, we have to determine whether a sutra is definitive or interpretable on the basis of logic. So, when we speak of the great vehicle philosophical schools, reason is more important than the scripture.
How do we determine whether something is interpretable? There are different types of scriptures belonging to the interpretable category, for instance, certain sutras mention that one's parents are to be killed. Now, since these sutras cannot be taken literally, at face value, they require further interpretation. The reference here to parents is to the contaminated actions and attachment which brings about rebirth in the future.
Similarly, in tantras such as Guhyasamaja the Buddha says that the Tathagata or Buddha is to be killed and that if you kill the Buddha, you will achieve supreme enlightenment.
It is obvious that these scriptures require further interpretion. However, other sutras are less obviously interpretable. The sutra which explains the twelve links of dependent arising states that because of the cause the fruits ensue. An example is that because of ignorance within, contaminated actions come about. Although the content of this type of sutra is true on one level, it is categorized as interpretable, because when ignorance is said to induce contaminated action, it does not refer to the ultimate point of view. It is only on the conventional level that something can produce something else. From the ultimate point of view, its nature is emptiness. So, because there is a further, deeper level not referred to in these sutras, they are said to be interpretable.
Definitive sutras are those sutras, like the Heart of Wisdom, in which the Buddha spoke of the ultimate nature of phenomena, that form is emptiness and emptiness is form; apart from form, there is no emptiness. Because such sutras speak of the ultimate nature of phenomena, their ultimate mode of existence, emptiness, they are said to be definitive. However, we should also note that there are different ways of discriminating between definitive and interpretable sutras among different Buddhist schools of thought.
In short, the texts of the Middle Way Consequentialist (Madhyamika Prasangika) school, particularly those by Nagarjuna and his disciple Chandrakirti, are definitive and expound the view of emptiness the Buddha taught to its fullest extent. The view of emptiness expounded in these texts is not contradicted by logical reasoning, but rather is supported by it.
Amongst the definitive sutras are also included sutras belonging to the third turning of the wheel of doctrine, particularly the Tathagata Essence Sutra, which is actually the fundamental source of such Middle Way treatises as the Sublime Continuum and the Collection of Praises written by Nagarjuna. Also included in the third turning were other sutras such as the Sutra Unravelling the Thought of the Buddha, which according to some Tibetan masters are also categorized as definitive.
These scholars (such as the Jonangpas) maintain a unique view of emptiness, which is technically called 'emptiness of other', and they speak of different kinds of emptiness qualifying different phenomena. They maintain that conventional phenomena are empty of themselves and ultimate phenomena are empty of conventional phenomena.
You could interpret this explanation of emptiness that conventional phenomena are empty of themselves, to mean that because conventional phenomena are not their own ultimate nature, they are empty of themselves. But these Tibetan scholars do not interpret it in such a way; they maintain that because phenomena are empty of themselves, they do not exist.
As we know from history that many masters belonging to this group of scholars actually achieved high realizations of the generation and completion stages of tantra, they must have had a profound understanding of their particular interpretation of emptiness. But if we were to interpret emptiness as things being empty of themselves in such a manner that they do not exist at all, it would be like saying that nothing exists at all.
Because they maintain that conventional phenomena do not exist, being empty of themselves, they maintain that their ultimate nature is a truly existent phenomenon that exists in its own right, is inherently existent. And when they speak of the emptiness of this ultimate truth they refer to its being empty of being a conventional phenomenon.
Dharmashri, the son of Yumo Mingyur Dorje, one the proponents of this view, stated in a text I once read that Nagarjuna's view of emptiness was a nihilistic view.
So, these systems of thought maintain that since conventional phenomena are empty of themselves, the only thing that exists is ultimate truth and that ultimate truth exists truly and inherently.
It is obvious that adherence to such a philosophical point of view directly contradicts the view of emptiness explained in the Perfection of Wisdom sutras, in which the Buddha has stated explicitly and clearly that as far as empty nature is concerned, there is no discrimination between conventional and ultimate phenomena. He has explained the emptiness of ultimate phenomena by using many different synonyms for ultimate truth, indicating that from form up to omniscience, all phenomena are equally empty.
Although Middle Way Consequentialists, proponents of the highest Buddhist philosophical tenets, speak of phenomena being empty and having an empty nature, this is not to say that phenomena do not exist at all. Rather that phenomena do not exist in or of themselves, in their own right, or inherently. The fact is that phenomena have the characteristics of existence, such as arising in dependence on other factors or causal conditions. Therefore, lacking any independent nature, phenomena are dependent. The very fact that they are by nature dependent on other factors is an indication of their lacking an independent nature. So, when Middle Way Consequentialists speak of emptiness, they speak of the dependent nature of phenomena in terms of dependent arising. Therefore, an understanding of emptiness does not contradict the conventional reality of phenomena.
Because phenomena arise in dependence on other factors, causal conditions and so forth, the Middle Way Consequentialists use their dependent nature as the final ground for establishing their empty nature. Lacking an independent nature, they lack inherent existence. The reasoning of dependent arising is very powerful, not only because it dispels the misconception that things exist inherently, but because at the same time it protects a person from falling into the extreme of nihilism.
In Nagarjuna's own writings, we find that emptiness has to be understood in the context of dependent arising. In the Fundamental Text Called Wisdom, Nagarjuna says, 'Since there is no phenomenon which is not a dependent arising, there is no phenomenon which is not empty.
It is clear that Nagarjuna’s view of emptiness has to be understood in the context of dependent arising, not only from his own writings, but also those of later commentators such as Buddhapalita, who is very concise but clear, and Chandrakirti in his Commentary on Nagarjuna's 'Treatise on the Middle Way', Clear Words, his Supplement to (Nagarjuna's) 'Treatise on the Middle Way' his auto-commentary to it and also his Commentary on Aryadeva's 'Four Hundred'. If you were to compare all these texts, it would become very clear that the view of emptiness as expounded by Nagarjuna has to be understood in terms of dependent arising. And when you read these commentaries, you begin to feel great appreciation for Nagarjuna.
This is a brief explanation of the sutra system of the Buddhist path.